# GNU Gengetopt 2.23

## Table of Contents

- Gengetopt
- Audience
- Gengetopt Copying Conditions
- 1 Installation
  - 1.1 Download
  - 1.2 Anonymous Git Checkout
  - 1.3 What you need to build gengetopt
- 2 Basic Usage
- 3 Invoking gengetopt
- 4 Terminology
- 5 Options with enumerated values
- 6 Group options
- 7 Mode options
- 8 Parser function additional parameters
- 9 Configuration files
  - 9.1 Further details on the configuration file parser
- 10 Multiple Options
- 11 String Parsers and Multiple Parsers
- 12 What if getopt_long is not available?
  - 12.1 Include the `getopt_long` code into the generated parser
  - 12.2 Use automake/autoconf to check for the existence of `getopt_long`
    - 12.2.1 Use Gnulib
    - 12.2.2 Use getopt_long sources
- 13 Known Bugs and Limitations
  - 13.1 Getopt and subsequent calls
- 14 Mailing Lists
- Index

Next: Audience, Previous: (dir), Up: (dir)

## Gengetopt

Gengetopt is a tool to write command line option parsing code for C programs.

This is Edition 2.23 of the Gengetopt manual.

This file documents GNU Gengetopt version 2.23.

This manual is for GNU Gengetopt (version 2.23, 3 June 2019), a tool to write command line option parsers for C programs.

Copyright © 2001 - 2011 Free Software Foundation, Inc.

> Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover Texts being “A GNU Manual,” and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled “GNU Free Documentation License.”

> (a) The FSF's Back-Cover Text is: “You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development.”

Next: Copying, Previous: Top, Up: Top

## Audience

Gengetopt is a tool to generate C code to parse the command line arguments `argc` and `argv` that are part of every C or C++ program. The generated code uses the C library function `getopt_long` to perform the actual command line parsing.

This manual is written for C and C++ programmers, specifically the lazy ones. If you've written any non-trivial C program, you've had to deal with argument parsing. It isn't particularly difficult, nor is it particularly exciting. It is one of the classic programming nuisances, which is why most books on programming leave it as an exercise for the reader. Gengetopt can save you from this work, leaving you free to focus on the interesting parts of your program.

Thus your program will be able to handle command line options such as:

         myprog --input foo.c -o foo.o --no-tabs -i 100 *.class

And both long options (those that start with `--`) and short options (start with `-` and consist of only one character) can be handled (see Terminology for further details). For standards about short and long options you may want to take a look at the GNU Coding Standards.

Gengetopt can also generate a function to save the command line options into a file (see Basic Usage), and a function to read the command line options from a file (see Configuration files). Of course, these two kinds of files are compliant.

Generated code works also if you use GNU Autoconf and GNU Automake and it is documented with Doxygen comments. In particular, `PACKAGE`, `PACKAGE_NAME` and `VERSION` are used in the generated code to print information.

Next: Installation, Previous: Audience, Up: Top

## Gengetopt Copying Conditions

Gengetopt is free software; you are free to use, share and modify it under the terms of the GNU General Public License that accompanies this manual.

The code that Gengetopt generates is also free software; however it is licensed with a simple all-permissive license instead of the GPL or LGPL. You are free to do anything you like with the generated code, including incorporating it into or linking it with proprietary software.

Gengetopt was originally written by Roberto Arturo Tena Sanchez. It is currently maintained by Tomas Volf.

A primordial version of Terminology was written by Adam Greenblatt.

Next: Basic Usage, Previous: Copying, Up: Top

## 1 Installation

See the file `INSTALL` for detailed building and installation instructions; anyway if you're used to compiling Linux software that comes with sources you may simply follow the usual procedure, i.e. untar the file you downloaded in a directory and then:

         cd <source code main directory>
         ./configure
         make
         make install

Note: unless you specify a different install directory by `--prefix` option of configure (e.g. `./configure --prefix=<your home>`), you must be root to run `make install`.

Files will be by default installed in the following directories:

`executables`
  `/prefix/bin`
`docs`
  `/prefix/share/doc/gengetopt`
`examples`
  `/prefix/share/doc/gengetopt/examples`
`additional files`
  `/prefix/share/gengetopt`

Default value for prefix is `/usr/local` but you may change it with `--prefix` option to configure.

### 1.1 Download

You can download it from GNU's ftp site: ftp://ftp.gnu.org/gnu/gengetopt or from one of its mirrors (see https://www.gnu.org/prep/ftp.html). You can also use https protocol to benefit from encryption: https://ftp.gnu.org/gnu/gengetopt/. Binaries are not distributed, please either use your distribution's version or compile your own.

Archives are digitally signed by me (Tomas Volf) with GNU gpg (https://www.gnupg.org). My GPG public key can be found at my home page ({No value for `wolf_homepage'}).

### 1.2 Anonymous Git Checkout

This project's git repository can be checked out through the following clone instruction1:

         git clone git://git.savannah.gnu.org/gengetopt.git

Further instructions can be found at the address:

https://savannah.gnu.org/projects/gengetopt.

And the git repository can also browsed on-line at

https://git.savannah.gnu.org/cgit/gengetopt.git.

Please note that this way you will get the latest development sources of Gengetopt, which may also be unstable. This solution is the best if you intend to correct/extend this program: you should send me patches against the latest git repository sources.

If, on the contrary, you want to get the sources of a given release, through git, say, e.g., version X.Y.Z, you must specify the tag `rel_X_Y_Z`.

When you compile the sources that you get from the git repository, before running the `configure` and `make` commands, for the first time, you must run the command:

         autoreconf -i

This will run the autotools commands in the correct order, and also copy possibly missing files. You should have installed recent versions of `automake`, `autoconf` and `libtool` in order for this to succeed.

### 1.3 What you need to build gengetopt

Gengetopt has been developed under GNU/Linux, using gcc (C++), and bison (yacc) and flex (lex), and ported under Win32 with Cygnus C/C++compiler, available at https://www.cygwin.com.

For developing gengetopt, I use the excellent GNU Autoconf2, GNU Automake3 and GNU Libtool4. Since version 2.19 I also started to use Gnulib - The GNU Portability Library5, “a central location for common GNU code, intended to be shared among GNU packages” (for instance, I rely on Gnulib for checking for the presence and correctness of `getopt_long` function, Use Gnulib).

Moreover GNU Gengen (https://www.gnu.org/software/gengen) is used for automatically generating the code that generates the command line parser.

Actually, you don't need all these tools above to build gengetopt because I provide generated sources, unless you want to develop gengetopt.

The code generated by gengetopt relies on the `getopt_long` function that is usually in the standard C library; however, there may be some implementations of the C library that don't include it; we refer to No getopt_long, for instructions on how to check whether getopt_long is part of the library and how to deal with their lacking (using autoconf and automake).

Next: Invoking gengetopt, Previous: Installation, Up: Top

## 2 Basic Usage

The command line options, which have to be handled by gengetopt generated function, are specified in a file (typically with `.ggo` extension). This file consists of sentences with the formats shown below (these sentences are allowed to span more than one line). Statements in {} are optional (the `option` sentences need not to be given in separate lines):

         package "<packname>"
         version "<version>"
         purpose "<purpose>"
         usage "<usage>"
         description "<description>"
         versiontext "<versiontext>"

         args "<command line options>"

         option <long> <short> "<desc>"
         	{details="<detailed description>"}
         	{argtype} {typestr="<type descr>"}
         	{values="<value1>","<value2>",...}
         	{default="<default value>"}
         	{dependon="<other option>"}
         	{required} {argoptional} {multiple}
         	{hidden}

         option <long> <short> "<desc>" flag <on/off>

         section "section name" {sectiondesc="optional section description"}

         text "a textual sentence"

Where:

`package`
  This has the precedence over `PACKAGE` and `PACKAGE_NAME` generated by autoconf. This is required, unless you use autoconf.

  If `package` is specified, then it will be used to print the program name in the output of `--help` and `--version`, and also when printing errors (from within the generated parser). If it is not specified, then `PACKAGE` will be used when printing errors, and `PACKAGE_NAME` in the output of `--help` and `--version`. Note that if `PACKAGE_NAME` is empty, then `PACKAGE` will be used also in this case.

`version`
  This has the precedence over `VERSION` generated by autoconf. This is required, unless you use autoconf.
`purpose`
  What the program does (even on more than one line), it will be printed with the help, before the usage string. Optional.
`usage`
  The “Usage” string that will be printed with the help6. If not specified, it will be generated automatically. Optional.
`description`
  The “Description” string that will be printed with the help7, after the usage string. Optional.
`versiontext`
  Additional information that will be printed after the program name and version in the output of `--version`. This would be used, for example, to display copyright and licensing information.
`args`
  With `args`8 you can specify options that will be added to the command line options of gengetopt itself. For instance, if you always run gengetopt on your input file with the options `--no-handle-error --string-parser -u`, you can add these options in the input file like this:

                args "--no-handle-error --string-parser -u"

  and remove those recurrent options from the command line. Optional.

`long`
  The long option, a double quoted string with upper and lower case characters, digits, a dash (`-`) and a dot (`.`). No spaces allowed. The name of the variables generated to store arguments (see later in this section) are long options converted to be legal C variable names. This means that `.` and `-` are both replaced by `_`.

`short`
  The short option, a single upper or lower case char, or a digit. If a `-` is specified, then no short option is considered for the long option (thus long options with no associated short options are allowed). Since version 2.22 you can also specify `?` as the short option.

`desc`
  This description will be printed during the output of `--help`. Wrapping will be automatically performed.
`details`
  This is an extended description string for the option that will be printed (after the option) during the output of `--detailed-help`9, which will be automatically generated. Thus, these further details will NOT be printed with `--help`. Wrapping will be automatically performed. Optional.

  Note that if `--strict-hidden` is used, options that are hidden (See Hidden options.) will not appear in the output of `--detailed-help`, even if those options have details.

`argtype`
  `string`, `int`, `short`, `long`, `float`, `double`, `longdouble` or `longlong`. If the option is an enumerated one (see Options with enumerated values) the type can also be `enum`. If no type is specified the option does not accept an argument.

`typestr`
  a description for the type of the values for the option. This will be used during the output of `--help` (e.g., `"filename"` instead of simply `STRING`, or `"portnumber"` instead of simply `INT`).

`values`
  a list of strings containing all the possible values that can be passed to the option. If not specified, the type is considered string10. For this kind of options, the type can also be `enum`. More on this feature can be found in Options with enumerated values.

`default`
  an optional default value for the option. The value must always be specified as a double quoted string. It is possible to combine this with the `multiple` flag (Multiple Options) but only by giving a single default value. It is not possible to specify a list of default values.

`dependon`
  this option depends on another option (whose long name description is specified). If this option is given at command line but not the option it depends on, an error will be generated.

`required`
  `required` or `optional`. This specifies whether such option must be given at each program invocation. These keywords were introduced in release 2.17. Before, you had to use the keywords `yes` or `no`. You can still use these keywords but their use is not advised since they are not much explicative.

  If not specified, an option is considered mandatory; if you do not want this behavior, you can require that by default options are considered optional, by using the command line option `--default-optional`11.

`argoptional`
  If this flag is specified then this option has an argument that is optional. In this case, when you specify the argument at command line, please use `=` in case you use a long option, and avoid spaces if you use short option. For instance, if the option with optional argument is `-B|--bar`, use the following command line syntax: `-B15` or `--bar=15`, and NOT the following one `-B 15` nor `--bar 15`.

  By using this specification together with `default` you can obtain an option that even if not explicitly specified will have the default value, and if it is specified without an argument it will have, again, the default value.

`multiple`
  If this flag is specified then this option can be specified more than once at command line; all the values for this option are stored in an array. You can also specify the number of occurrences that a multiple option must be specified. Notice that this is independent from the `required` flag. See Multiple Options.

`hidden`

  If an option is “hidden” it will not appear in the output of `--help` but it can still be specified at command line12. When hidden options are used, the command line option `--full-help` will also be generated. This will also print hidden options13. Hidden options are also displayed in the output of `--detailed-help`, if it is present, along with any details that those options have.

  Note that when `--strict-hidden` is used, hidden options do not appear as described above, although they can still be given on the comand line. That is to say, the `--full-help` option is not generated, and hidden options do not appear in the output of `--detailed-help`, even if they have details.

`on/off`
  `on` or `off`. This is the state of the flag when the program starts. If user specifies the option, the flag toggles.

For strings (delimited by `"`) the following convention is adopted14: a string spanning more than one line will be interpreted with the corresponding line breaks; if the line break is not desired one can use the backslash `\` to break the line without inserting a line break. A line break in a string can also be inserted with the string `\n`. Here are some examples:

         "This string will be interpreted
         into two lines exactly as it is"

         "This string is specified with two lines \
         but interpreted as specified in only one line \
         i.e., without explicit line break"

         "This string\nwill have a line break"

Moreover, if the character `"` must be specified in the string, it will have to be escaped with the backslash15:

         "This string contains \"a quoted string\" inside"

The part that must be provided in the correct order is

         option <long> <short> "<desc>"

while the other specifications can be given in any order16. Thus, for instance

         option <long> <short> "<desc>" {argtype} {typestr="<type descr>"}

is the same as

         option <long> <short> "<desc>" {typestr="<type descr>"} {argtype}

Comments begin with `#` (except in strings) and ends in the end of line.

Notice that the options `-h,--help` and `-V,--version` are added automatically; however, if you specify an option yourself that has `h` as short form, then only `--help` is added17. The same holds for `-V,--version`.

In case hidden options are used, See Hidden options, the command line option `--full-help` will also be generated. This will print also the hidden options18.

Note, though, that when `--strict-hidden` is used, this is not the case and `--full-help` is not generated.

If there's at least one option with `details`, the command line option `--detailed-help` will also be generated. This will print also the details for options and hidden options19 (except when `--strict-hidden` is used).

Options can be part of sections, that provide a more meaningful descriptions of the options. A section can be defined with the following syntax (the `sectiondesc` is optional) and all the options following a section declaration are considered part of that sections:

         section "section name" {sectiondesc="optional section description"}

Notice that the separation in sections is stronger than separation in groups of mutually exclusive options (see Group options). Furthermore, sections should not be inserted among group options (but only externally). A section makes sense only if it is followed by some options. If you don't specify any option after a section, that section will not be printed at all. If you need to simply insert some text in the output of `--help`, then you must use `text`, explained in the next paragraph.

You can insert, among options, a textual string that will be printed in the output of `--help`20:

         text "\nA text description with possible line\nbreaks"

Of course, you can use this mechanism even to manually insert blank lines among options with an empty text string:

         text ""

You can also specify the list of `values` that can be passed to an option (if the type is not specified, the option has type `string`). More on this feature can be found in Options with enumerated values. If a value that is not in the list is passed, an error is raised. You can think of such options as enumerated options. It is not necessary to pass the complete value at the command line option: a non ambiguous prefix will do. For instance, if the accepted values are `"foo","bar","foobar"`, then you can pass at the command line the value `"b"` and the value `"bar"` will be selected, or the value `"foob"` and the value `"foobar"` will be selected; instead, passing the value `"fo"` will raise an ambiguity error.

Here's an example of such a file (the file is called `sample1.ggo`)

         # Name of your program
         package "sample1" # don't use package if you're using automake
         # Version of your program
         version "2.0"   # don't use version if you're using automake

         # Options
         option  "str-opt"         s "A string option, for a filename"
                 string typestr="filename"     optional
         text "\nA brief text description"
         text " before the other options.\n"
         option  "my-opt"          m "Another integer option, \
         this time the description of the option should be \"quite\" long to \
         require wrapping... possibly more than one wrapping :-) \
         especially if I\nrequire a line break"      int     optional
         option  "int-opt"         i "A int option"         int        yes
         section "more involved options"
                 sectiondesc="the following options\nare more complex"
         text ""
         option  "flag-opt"        - "A flag option"        flag       off
         option  "funct-opt"       F "A function option"    optional
             details="\nA function option is basically an option with no argument.\
           It can be used, e.g., to specify a specific behavior for a program.

         Well, this further explanation is quite useless, but it's only to \
         show an example of an option with details, \
         which will be printed only when --detailed-help is given \
         at the command line."
         section "last option section"
         option  "long-opt"        - "A long option"        long       optional
         option  "def-opt"         - "A string option with default"
                 string default="Hello" optional
         option  "enum-opt"         - "A string option with list of values"
                 values="foo","bar","hello","bye" default="hello" optional
         option  "secret"         S "hidden option will not appear in --help"
                 int optional hidden
         option  "dependant"         D
                 "option that depends on str-opt" int optional dependon="str-opt"
         text "\nAn ending text."

The simplest way to use gengetopt is to pass this file as the standard input, i.e.:

         gengetopt < sample1.ggo

By default gengetopt generates `cmdline.h` and `cmdline.c`. Otherwise we can specify these names with a command line option:

         gengetopt < sample1.ggo --file-name=cmdline1 --unnamed-opts

The option `--unnamed-opts` allows the generated command line parser to accept also names, without an option (for instance you can pass a file name without an option in front of it, and also use wildcards, such as `*.c`, `foo*.?` and so on). These are also called parameters (see Terminology). You can specify an optional description for these additional names (default is `FILES`).

In `cmdline1.h` you'll find the generated C struct:

         /** @file cmdline1.h
          *  @brief The header file for the command line option parser
          *  generated by GNU Gengetopt version 2.23
          *  http://www.gnu.org/software/gengetopt.
          *  DO NOT modify this file, since it can be overwritten
          *  @author GNU Gengetopt */

         #ifndef CMDLINE1_H
         #define CMDLINE1_H

         /* If we use autoconf.  */
         #ifdef HAVE_CONFIG_H
         #include "config.h"
         #endif

         #include <stdio.h> /* for FILE */

         #ifdef __cplusplus
         extern "C" {
         #endif /* __cplusplus */

         #ifndef CMDLINE_PARSER_PACKAGE
         /** @brief the program name (used for printing errors) */
         #define CMDLINE_PARSER_PACKAGE "sample1"
         #endif

         #ifndef CMDLINE_PARSER_PACKAGE_NAME
         /** @brief the complete program name (used for help and version) */
         #define CMDLINE_PARSER_PACKAGE_NAME "sample1"
         #endif

         #ifndef CMDLINE_PARSER_VERSION
         /** @brief the program version */
         #define CMDLINE_PARSER_VERSION "2.0"
         #endif

         /** @brief Where the command line options are stored */
         struct gengetopt_args_info
         {
           const char *help_help; /**< @brief Print help and exit help description.  */
           const char *detailed_help_help; /**< @brief Print help, including all details and hidden options, and exit help description.  */
           const char *full_help_help; /**< @brief Print help, including hidden options, and exit help description.  */
           const char *version_help; /**< @brief Print version and exit help description.  */
           char * str_opt_arg;	/**< @brief A string option, for a filename.  */
           char * str_opt_orig;	/**< @brief A string option, for a filename original value given at command line.  */
           const char *str_opt_help; /**< @brief A string option, for a filename help description.  */
           int my_opt_arg;	/**< @brief Another integer option, this time the description of the option should be \"quite\" long to require wrapping... possibly more than one wrapping :-) especially if I
           require a line break.  */
           char * my_opt_orig;	/**< @brief Another integer option, this time the description of the option should be \"quite\" long to require wrapping... possibly more than one wrapping :-) especially if I
           require a line break original value given at command line.  */
           const char *my_opt_help; /**< @brief Another integer option, this time the description of the option should be \"quite\" long to require wrapping... possibly more than one wrapping :-) especially if I
           require a line break help description.  */
           int int_opt_arg;	/**< @brief A int option.  */
           char * int_opt_orig;	/**< @brief A int option original value given at command line.  */
           const char *int_opt_help; /**< @brief A int option help description.  */
           int flag_opt_flag;	/**< @brief A flag option (default=off).  */
           const char *flag_opt_help; /**< @brief A flag option help description.  */
           const char *funct_opt_help; /**< @brief A function option help description.  */
           long long_opt_arg;	/**< @brief A long option.  */
           char * long_opt_orig;	/**< @brief A long option original value given at command line.  */
           const char *long_opt_help; /**< @brief A long option help description.  */
           char * def_opt_arg;	/**< @brief A string option with default (default='Hello').  */
           char * def_opt_orig;	/**< @brief A string option with default original value given at command line.  */
           const char *def_opt_help; /**< @brief A string option with default help description.  */
           char * enum_opt_arg;	/**< @brief A string option with list of values (default='hello').  */
           char * enum_opt_orig;	/**< @brief A string option with list of values original value given at command line.  */
           const char *enum_opt_help; /**< @brief A string option with list of values help description.  */
           int secret_arg;	/**< @brief hidden option will not appear in --help.  */
           char * secret_orig;	/**< @brief hidden option will not appear in --help original value given at command line.  */
           const char *secret_help; /**< @brief hidden option will not appear in --help help description.  */
           int dependant_arg;	/**< @brief option that depends on str-opt.  */
           char * dependant_orig;	/**< @brief option that depends on str-opt original value given at command line.  */
           const char *dependant_help; /**< @brief option that depends on str-opt help description.  */

           unsigned int help_given ;	/**< @brief Whether help was given.  */
           unsigned int detailed_help_given ;	/**< @brief Whether detailed-help was given.  */
           unsigned int full_help_given ;	/**< @brief Whether full-help was given.  */
           unsigned int version_given ;	/**< @brief Whether version was given.  */
           unsigned int str_opt_given ;	/**< @brief Whether str-opt was given.  */
           unsigned int my_opt_given ;	/**< @brief Whether my-opt was given.  */
           unsigned int int_opt_given ;	/**< @brief Whether int-opt was given.  */
           unsigned int flag_opt_given ;	/**< @brief Whether flag-opt was given.  */
           unsigned int funct_opt_given ;	/**< @brief Whether funct-opt was given.  */
           unsigned int long_opt_given ;	/**< @brief Whether long-opt was given.  */
           unsigned int def_opt_given ;	/**< @brief Whether def-opt was given.  */
           unsigned int enum_opt_given ;	/**< @brief Whether enum-opt was given.  */
           unsigned int secret_given ;	/**< @brief Whether secret was given.  */
           unsigned int dependant_given ;	/**< @brief Whether dependant was given.  */

           char **inputs ; /**< @brief unnamed options (options without names) */
           unsigned inputs_num ; /**< @brief unnamed options number */
         } ;

         /** @brief The additional parameters to pass to parser functions */
         struct cmdline_parser_params
         {
           int override; /**< @brief whether to override possibly already present options (default 0) */
           int initialize; /**< @brief whether to initialize the option structure gengetopt_args_info (default 1) */
           int check_required; /**< @brief whether to check that all required options were provided (default 1) */
           int check_ambiguity; /**< @brief whether to check for options already specified in the option structure gengetopt_args_info (default 0) */
           int print_errors; /**< @brief whether getopt_long should print an error message for a bad option (default 1) */
         } ;

         /** @brief the purpose string of the program */
         extern const char *gengetopt_args_info_purpose;
         /** @brief the usage string of the program */
         extern const char *gengetopt_args_info_usage;
         /** @brief the description string of the program */
         extern const char *gengetopt_args_info_description;
         /** @brief all the lines making the help output */
         extern const char *gengetopt_args_info_help[];
         /** @brief all the lines making the full help output (including hidden options) */
         extern const char *gengetopt_args_info_full_help[];
         /** @brief all the lines making the detailed help output (including hidden options and details) */
         extern const char *gengetopt_args_info_detailed_help[];

         /**
          * The command line parser
          * @param argc the number of command line options
          * @param argv the command line options
          * @param args_info the structure where option information will be stored
          * @return 0 if everything went fine, NON 0 if an error took place
          */
         int cmdline_parser (int argc, char **argv,
           struct gengetopt_args_info *args_info);

         /**
          * The command line parser (version with additional parameters - deprecated)
          * @param argc the number of command line options
          * @param argv the command line options
          * @param args_info the structure where option information will be stored
          * @param override whether to override possibly already present options
          * @param initialize whether to initialize the option structure my_args_info
          * @param check_required whether to check that all required options were provided
          * @return 0 if everything went fine, NON 0 if an error took place
          * @deprecated use cmdline_parser_ext() instead
          */
         int cmdline_parser2 (int argc, char **argv,
           struct gengetopt_args_info *args_info,
           int override, int initialize, int check_required);

         /**
          * The command line parser (version with additional parameters)
          * @param argc the number of command line options
          * @param argv the command line options
          * @param args_info the structure where option information will be stored
          * @param params additional parameters for the parser
          * @return 0 if everything went fine, NON 0 if an error took place
          */
         int cmdline_parser_ext (int argc, char **argv,
           struct gengetopt_args_info *args_info,
           struct cmdline_parser_params *params);

         /**
          * Save the contents of the option struct into an already open FILE stream.
          * @param outfile the stream where to dump options
          * @param args_info the option struct to dump
          * @return 0 if everything went fine, NON 0 if an error took place
          */
         int cmdline_parser_dump(FILE *outfile,
           struct gengetopt_args_info *args_info);

         /**
          * Save the contents of the option struct into a (text) file.
          * This file can be read by the config file parser (if generated by gengetopt)
          * @param filename the file where to save
          * @param args_info the option struct to save
          * @return 0 if everything went fine, NON 0 if an error took place
          */
         int cmdline_parser_file_save(const char *filename,
           struct gengetopt_args_info *args_info);

         /**
          * Print the help
          */
         void cmdline_parser_print_help(void);
         /**
          * Print the full help (including hidden options)
          */
         void cmdline_parser_print_full_help(void);
         /**
          * Print the detailed help (including hidden options and details)
          */
         void cmdline_parser_print_detailed_help(void);
         /**
          * Print the version
          */
         void cmdline_parser_print_version(void);

         /**
          * Initializes all the fields a cmdline_parser_params structure
          * to their default values
          * @param params the structure to initialize
          */
         void cmdline_parser_params_init(struct cmdline_parser_params *params);

         /**
          * Allocates dynamically a cmdline_parser_params structure and initializes
          * all its fields to their default values
          * @return the created and initialized cmdline_parser_params structure
          */
         struct cmdline_parser_params *cmdline_parser_params_create(void);

         /**
          * Initializes the passed gengetopt_args_info structure's fields
          * (also set default values for options that have a default)
          * @param args_info the structure to initialize
          */
         void cmdline_parser_init (struct gengetopt_args_info *args_info);
         /**
          * Deallocates the string fields of the gengetopt_args_info structure
          * (but does not deallocate the structure itself)
          * @param args_info the structure to deallocate
          */
         void cmdline_parser_free (struct gengetopt_args_info *args_info);

         /**
          * Checks that all the required options were specified
          * @param args_info the structure to check
          * @param prog_name the name of the program that will be used to print
          *   possible errors
          * @return
          */
         int cmdline_parser_required (struct gengetopt_args_info *args_info,
           const char *prog_name);

         extern const char *cmdline_parser_enum_opt_values[];  /**< @brief Possible values for enum-opt. */

         #ifdef __cplusplus
         }
         #endif /* __cplusplus */
         #endif /* CMDLINE1_H */

First of all, notice that the `argv` parameter (typically corresponding to the homonimous argument of your program's `main` function) is declared as `char **` and not as `char *const *`21. Actually, the version of `getopt_long` in libc uses prototypes with `char *const *argv` that are incorrect because getopt_long and getopt_long_only can permute argv; this is required for backward compatibility (e.g., for LSB 2.0.1)22. So, it is better to declare `argv` as `char **` in the generated parser functions.

The `<option>_given` field is set to 1 when an argument for `<option>` has been specified (otherwise it is 0)23. This fields also counts the times a multiple option is specified (see Multiple Options). If the option accepts an argument and it is not of `flag` type The `<option>_arg` field is set to the value passed at the command line. The `<option>_arg` field has the corresponding C type specified in the file passed to gengetopt.

Notice that if an option has a default value, then the corresponding `<option>_arg` will be initialized with that value but the corresponding `<option>_given` will NOT be initialized to 1. Thus, `<option>_given` will effectively inform you if the user has specified that command line option.

The additional field `<option>_orig` is always a string containing the original value passed at the command line. This may be different, for instance, in case of numerical arguments: gengetopt converts the passed value (a string) into the corresponding numerical type; due to conversions, float representations, etc., this may not correspond exactly to the original value passed at command line. It can also be different when enumerated options are used (see above): in particular the `<option>_arg` field will contain a value taken from the specified list, while `<option>_orig` contains the (non-ambiguous) prefix specified at the command line.

The user can always access this original value by using `<option>_orig` instead of `<option>_arg`, as he sees fit24. For instance, gengetopt itself uses the original value when it saves the command line options into a file (see the `_file_save` function in the following). However, apart from very specific command line processing, the user might hardly need the `<option>_orig` field, and can be always safely use `<option>_arg`.

The `<option>_help` contains the string (concerning this very option) that is printed when `--help` command line is given.

If it is of `flag` type, only the field `<option>_flag` is generated.

The strings `cmdline_parser_purpose` and `cmdline_parser_usage` contain the `purpose` as specified in the input file and the generated “usage” string as printed when `--help` command line is given. Finally, the string array `cmdline_parser_help` contains the strings (one for each option) printed when `--help` command line is given (this array is terminated by a null string element). If hidden options are used also the `cmdline_parser_full_help` array is available (containing also help strings concerning hidden options). If at least one option has `details`, then the `cmdline_parser_detailed_help` array is available (containing also help strings concerning hidden options and details for options). All these strings can be used by the programmer to build a customized help output25.

Even if `<option>_given` is 0, the corresponding `<option>_arg` is set to default value (if one has been specified for `<option>`). However, in this case, the `<option>_orig` is set to `NULL`.

Notice that by default the generated function is called `cmdline_parser` (see the command line options below, to override this name), and it takes the arguments that main receives and a pointer to such a struct, that it will be filled. Another version, `cmdline_parser2`, can be specified more arguments. Since you typically need this second version only in conjunction with other “kinds” of parsers such as configuration files and multiple parsers, you can find more details about it in Configuration files.

IMPORTANT: The array passed to the parser function (that in turn is passed to `getopt_long`) is expected to have in the first element (of index 0) the name of the program that was invoked. This will be used, for instance, for printing possible errors.

`cmdline_parser_free` can be called to deallocate memory allocated by the parser for string and multiple options.

`cmdline_parser_init` can be called to initialize the struct (it is not mandatory, since it is done automatically by the command line parser).

`cmdline_parser_file_save`26 can be used to save the command line options into a file. The contents of this file are consistent with the configuration files (Configuration files). Notice that if an option has a default value, this option will be saved into the file only if it was passed explicitly at command line (or read from a configuration file), i.e., default values will not be saved into the file. Alternatively, you can use `cmdline_parser_dump`27 that takes as the first parameter an already open stream (`FILE *`) instead of a file name.

And here's how these functions can be used inside the main program:

         /* main1.cc */
         /* we try to use gengetopt generated file in a C++ program */
         /* we don't use autoconf and automake vars */

         #ifdef HAVE_CONFIG_H
         #include "config.h"
         #endif

         #include <iostream>
         #include "stdlib.h"

         #include "cmdline1.h"

         using std::cout;
         using std::endl;

         int
         main (int argc, char **argv)
         {
           gengetopt_args_info args_info;

           cout << "This one is from a C++ program" << endl ;
           cout << "Try to launch me with some options" << endl ;
           cout << "(type sample1 --help for the complete list)" << endl ;
           cout << "For example: ./sample1 *.* --funct-opt" << endl ;

           /* let's call our cmdline parser */
           if (cmdline_parser (argc, argv, &args_info) != 0)
             exit(1) ;

           cout << "Here are the options you passed..." << endl;

           for ( unsigned i = 0 ; i < args_info.inputs_num ; ++i )
             cout << "file: " << args_info.inputs[i] << endl ;

           if ( args_info.funct_opt_given )
             cout << "You chose --funct-opt or -F." << endl ;

           if ( args_info.str_opt_given )
             cout << "You inserted " << args_info.str_opt_arg << " for " <<
               "--str-opt option." << endl ;

           if ( args_info.int_opt_given )
             cout << "This is the integer you input: " <<
               args_info.int_opt_arg << "." << endl;

           if (args_info.flag_opt_given)
             cout << "The flag option was given!" << endl;

           cout << "The flag is " << ( args_info.flag_opt_flag ? "on" : "off" ) <<
             "." << endl ;

           if (args_info.enum_opt_given) {
             cout << "enum-opt value: " << args_info.enum_opt_arg << endl;
             cout << "enum-opt (original specified) value: "
         	 << args_info.enum_opt_orig << endl;
           }

           if (args_info.secret_given)
             cout << "Secret option was specified: " << args_info.secret_arg
         	 << endl;

           cout << args_info.def_opt_arg << "! ";

           cout << "Have a nice day! :-)" << endl ;

           cmdline_parser_free (&args_info); /* release allocated memory */

           return 0;
         }

Now you can compile `main1.cc` and the `cmdline1.c` generated by gengetopt and link all together to obtain `sample1` executable:

         gcc -c cmdline1.c
         g++ -c main1.cc
         g++ -o sample1 cmdline1.o main1.o

(Here we assume that `getopt_long` is included in the standard C library; see Installation and No getopt_long).

Now let's try some tests with this program:

         $ ./sample1 -s "hello" --int-opt 1234
         This one is from a C++ program
         Try to launch me with some options
         (type sample1 --help for the complete list)
         For example: ./sample1 *.* --funct-opt
         Here are the options you passed...
         You inserted hello for --str-opt option.
         This is the integer you input: 1234.
         The flag is off.
         Have a nice day! :-)

You can also pass many file names to the command line (this also shows how flags work):

         $ ./sample1 *.h -i -100 -x
         This one is from a C++ program
         Try to launch me with some options
         (type sample1 --help for the complete list)
         For example: ./sample1 *.* --funct-opt
         Here are the options you passed...
         file: cmdline1.h
         file: cmdline2.h
         file: cmdline.h
         file: getopt.h
         This is the integer you input: -100.
         The flag is on.
         Have a nice day! :-)

And if we try to omit the `--int-opt` (or `-i`), which is required, we get an error:

         $ ./sample1
         This one is from a C++ program
         Try to launch me with some options
         (type sample1 --help for the complete list)
         For example: ./sample1 *.* --funct-opt
         sample1: `--int-opt' (`-i') option required!

Now, let's test the enumerated options, notice the use of a prefix for specifying an acceptable value, and the difference between the actual passed value and the one recorded in `<option>_arg`:

         $ ./sample1 -i 10 --enum-opt h
         ...
         enum-opt value: hello
         enum-opt (original specified) value: h
         ...

While the next one raises an ambiguity error (between `"bar"` and `"bye"`):

         $ ./sample1 -i 10 --enum-opt b
         ...
         ./sample1: ambiguous argument, "b", for option `--enum-opt'

Here is the output of `--help` of the parser generated from `sample1.ggo` by specifying the following options to gengetopt: `--long-help -u --show-required` (see Invoking gengetopt for further explanation for these command line options).

         This one is from a C++ program
         Try to launch me with some options
         (type sample1 --help for the complete list)
         For example: ./sample1 *.* --funct-opt
         Usage: sample1 -iINT|--int-opt=INT [-h|--help] [--detailed-help] [--full-help]
                  [-V|--version] [-sfilename|--str-opt=filename] [-mINT|--my-opt=INT]
                  [--flag-opt] [-F|--funct-opt] [--long-opt=LONG] [--def-opt=STRING]
                  [--enum-opt=STRING] [-DINT|--dependant=INT] [FILE]...

           -h, --help              Print help and exit
               --detailed-help     Print help, including all details and hidden options,
                                     and exit
               --full-help         Print help, including hidden options, and exit
           -V, --version           Print version and exit
           -s, --str-opt=filename  A string option, for a filename

         A brief text description before the other options.

           -m, --my-opt=INT        Another integer option, this time the description of
                                     the option should be "quite" long to require
                                     wrapping... possibly more than one wrapping :-)
                                     especially if I
                                     require a line break
           -i, --int-opt=INT       A int option (mandatory)

         more involved options:
           the following options
           are more complex
               --flag-opt          A flag option  (default=off)
           -F, --funct-opt         A function option

         last option section:
               --long-opt=LONG     A long option
               --def-opt=STRING    A string option with default  (default=`Hello')
               --enum-opt=STRING   A string option with list of values  (possible
                                     values="foo", "bar", "hello", "bye"
                                     default=`hello')
           -D, --dependant=INT     option that depends on str-opt

         An ending text.

Notice how `filename` is printed instead of `STRING` for the option `--str-opt` (since `typestr` was used in the `sample1.ggo` file) and how the description of `--my-opt` is wrapped to 80 columns, and how the `\n` is actually interpreted as a newline request. Also the usage string is wrapped. Moreover, since `-S,--secret` is an hidden option (See Hidden options.) it is not printed; if you wanted that to be printed, you should use `--full-help`. The option `--func-opt` has also the `details`, but they are not printed with `--help`.

Finally, notice how the `text` strings are printed in the help output (and the empty line after the “more involved options” section achieved with an empty `text` string).

Instead, here is the output of `--detailed-help` of the parser generated from `sample1.ggo`. You may want to compare this output with the one produced by `--help` (See Output of `--help`.); in particular, you may notice that the hidden option `--secret` is actually printed and the details of `--func-opt` are printed too:

         This one is from a C++ program
         Try to launch me with some options
         (type sample1 --help for the complete list)
         For example: ./sample1 *.* --funct-opt
         Usage: sample1 -iINT|--int-opt=INT [-h|--help] [--detailed-help] [--full-help]
                  [-V|--version] [-sfilename|--str-opt=filename] [-mINT|--my-opt=INT]
                  [--flag-opt] [-F|--funct-opt] [--long-opt=LONG] [--def-opt=STRING]
                  [--enum-opt=STRING] [-DINT|--dependant=INT] [FILE]...

           -h, --help              Print help and exit
               --detailed-help     Print help, including all details and hidden options,
                                     and exit
               --full-help         Print help, including hidden options, and exit
           -V, --version           Print version and exit
           -s, --str-opt=filename  A string option, for a filename

         A brief text description before the other options.

           -m, --my-opt=INT        Another integer option, this time the description of
                                     the option should be "quite" long to require
                                     wrapping... possibly more than one wrapping :-)
                                     especially if I
                                     require a line break
           -i, --int-opt=INT       A int option (mandatory)

         more involved options:
           the following options
           are more complex
               --flag-opt          A flag option  (default=off)
           -F, --funct-opt         A function option

           A function option is basically an option with no argument.  It can be used,
           e.g., to specify a specific behavior for a program.

           Well, this further explanation is quite useless, but it's only to show an
           example of an option with details, which will be printed only when
           --detailed-help is given at the command line.

         last option section:
               --long-opt=LONG     A long option
               --def-opt=STRING    A string option with default  (default=`Hello')
               --enum-opt=STRING   A string option with list of values  (possible
                                     values="foo", "bar", "hello", "bye"
                                     default=`hello')
           -S, --secret=INT        hidden option will not appear in --help
           -D, --dependant=INT     option that depends on str-opt

         An ending text.

If you're curious you may want to take a look at the generated C file `cmdline1.c`.

You may find other examples in `/prefix/share/doc/gengetopt/examples` or in the `tests` of the source tarbal.

Next: Terminology, Previous: Basic Usage, Up: Top

## 3 Invoking gengetopt

This is the output of `gengetopt --help`:

         gengetopt

         This program generates a C function that uses getopt_long function
         to parse the command line options, validate them and fill a struct.

         Usage: gengetopt [OPTION]...

           -h, --help                    Print help and exit
               --detailed-help           Print help, including all details and hidden
                                           options, and exit
               --full-help               Print help, including hidden options, and exit
           -V, --version                 Print version and exit

         Main options:

           -i, --input=filename          input file (default std input)
           -f, --func-name=name          name of generated function
                                           (default=`cmdline_parser')
           -a, --arg-struct-name=name    name of generated args info struct
                                           (default=`gengetopt_args_info')
           -F, --file-name=name          name of generated file  (default=`cmdline')
               --output-dir=path         output directory
               --header-output-dir=path  header output directory
               --src-output-dir=path     source output directory
           -c, --c-extension=ext         extension of c file  (default=`c')
           -H, --header-extension=ext    extension of header file  (default=`h')
           -l, --long-help               long usage line in help
               --default-optional        by default, an option is considered optional if
                                           not specified otherwise
           -u, --unnamed-opts[=STRING]   accept options without names (e.g., file names)
                                           (default=`FILE')

         The parser generated is thought to be used to parse the command line arguments.
         However, you can also generate parsers for configuration files, or strings that
         contain the arguments to parse, by using the following two options.

           -C, --conf-parser             generate a config file parser
           -S, --string-parser           generate a string parser (the string contains
                                           the command line)

         Additional options:
           -G, --include-getopt          adds the code for getopt_long in the generated
                                           C file
           -n, --no-handle-help          do not handle --help|-h automatically
               --no-help                 do not add --help|-h automatically
           -N, --no-handle-version       do not handle --version|-V automatically
               --no-version              do not add --version|-V automatically
           -e, --no-handle-error         do not exit on errors
               --show-required[=STRING]  in the output of help will specify which
                                           options are mandatory, by using the optional
                                           passed string  (default=`(mandatory)')
               --strict-hidden           completely hide hidden options
           -g, --gen-version             put gengetopt version in the generated file
                                           (default=on)
               --set-package=STRING      set the package name (override package defined
                                           in the .ggo file)
               --set-version=STRING      set the version number (override version
                                           defined in the .ggo file)
               --show-help               show the output of --help instead of generating
                                           code
               --show-full-help          show the output of --full-help (i.e., including
                                           hidden options) instead of generating code
               --show-detailed-help      show the output of --detailed-help (i.e.,
                                           including details and hidden options) instead
                                           of generating code
               --show-version            show the output of --version instead of
                                           generating code

         Please refer to the info manual for further explanations.

The options should be clear; in particular:

`--func-name`
  if no `--func-name` is given, `cmdline_parser` is taken by default;
`--output-dir`
  if no `--output-dir`28 is given, the files are generated in the current directory;
`--src-output-dir`
`--header-output-dir`
  With these options29 the generated C file and the corresponding generated header files can be generated in different directories;
`--arg-struct-name`
  allows to specify the name of the generated struct for command line arguments (default is `gengetopt_args_info`)
`--long-help`
  the “Usage” line reports all the options; this may be unpleasant if options are many;
`--default-optional`
  If this command line option is given, by default, options are considered optional (if not explicitly specified otherwise). Otherwise, options are considered mandatory (if not explicitly specified otherwise).
`--unnamed-opts`
  the program will accept also options without a name, which, in most case, means that we can pass many file names to the program (see the example in Basic Usage, where we call `sample1 *.h`). You can specify an optional description for these additional names (default is `FILES`).
`--no-handle-help`
`--no-handle-version`
  if `--no-handle-help` (`--no-handle-version`) is given the command line option `--help|-h` (`--version|-V`) is not handled automatically, so the programmer will be able to print some other information; then the function for printing the standard help (version) response can be used; this function is called `<parser-name>_print_help` (`<parser-name>_print_version`), where `<parser-name>` is the name specified with `--func-name` or the default, `cmdline_parser`. In case hidden options are used, See Hidden options, also the function `<parser-name>_print_full_help` will be generated; if `details` are used for at least one option, then also the function `<parser-name>_print_detailed_help` will be generated. Notice that, although the programmer can handle these options manually, the parser will return after finding one of these options: the other command line options, if any, will be ignored. In case you want to have full control on `--help|-h`, `--version|-V`, you should use the following options:
`--no-help`
`--no-version`
  With these options30 you can disable the automatic addition of options `--help|-h` and `--version|-V`, respectively. The programmer will then be able to add these options in the input file and handle them as he sees fit. Notice that `--no-help` will also disable the automatic options `--detailed-help` and `--full-help`. The programmer can still define options with short character `h` and `V` as he wants, but he cannot define options `help` and `version`, unless he specifies `--no-help` and `--no-version`, respectively (otherwise an error will be printed). An example using these options and manually handles `--help` and `--version` can be found in `test_manual_help_cmd.ggo` and `test_manual_help.c` in the `examples` directory.
`--no-handle-error`
  if `--no-handle-error` is given, an error in the parsing does not provoke the exit of the program; instead, since the parser function, in case of an error, returns a value different 0, the program can print a help message, as gengetopt itself does in case of an error (try it!).
`--show-required`
  if `--show-required` is given, possibly with a string, in the output of `--help` will be made explicit which options are actually required, See Basic Usage.
`--strict-hidden`
  when given, this causes hidden options to become really hidden. That is to say, the `--full-help` option will not be added, and hidden options will not show-up in the output of `--detailed-help`, even if they have details. See Hidden options.
`--gen-version`
  is a flag (default on) that when disabled does not put in the output file the gengetopt version (it is useful for testing purposes).
`--conf-parser`
  Detailed in Configuration files.
`--string-parser`
  Detailed in String Parsers and Multiple Parsers.
`--include-getopt`
  Adds the code for `getopt_long` into the generated parser C file. This will make your generated parser much bigger, but it will be compiled in any system, even if `getopt_long` is not part of the C library where your program is being compiled. See also No getopt_long.
`--show-help`
`--show-full-help`
`--show-version`
  only make gengetopt show the output of `--help`, `--full-help` and `--version` command lines without generating any code, See Automatically added options. For instance, I use the `--show-help` option to generate a texinfo file with the output of help (this also shows an example of use of `--set-package` and `--set-version`):

                ../src/gengetopt --show-help -i ../src/cmdline.ggo \
                	--set-package="gengetopt" \
                	--set-version="" > help_output.texi

You may have already guessed it: gengetopt uses gengetopt itself for command line options, and its specification file is `cmdline.ggo` in the source directory. In particular the command line for gengetopt itself is generated with the following command:

         gengetopt --input=cmdline.ggo --no-handle-version \
         	--no-handle-help --no-handle-error

Indeed when `--help|-h` is passed on the command line, gengetopt will call `cmdline_parser_print_help()` and then the lines for reporting bugs. When `--version|-V` is passed, it will call cmdline_parser_print_version() and then prints a copyright. If an error occurs it prints a message on the screen:

         $ ./gengetopt --zzzz
         ./gengetopt: unrecognized option `--zzzz'
         Run gengetopt --help to see the list of options.

Next: Options with enumerated values, Previous: Invoking gengetopt, Up: Top

## 4 Terminology

An argument is an element of the `argv` array passed into your C or C++ program by your operating system.

An option is an argument that begins with `-`, or `--`.

A value is an argument, or part of an argument, that is associated with a particular option (an option may also not accept any value). For example, in

         > ls --width=80

`ls` is called with one argument, `--width=80`, which is an option that has a value, `80`, while in

         > ls --width 80

`ls` is called with two arguments, `--width`, which is an option, and `80` which might or might not be a value. In this case, whether the `80` is treated as a value associated with the preceding `--width` option, or as the name of a file to list depends on how `ls` parses the `--width` option.

The order in which options are specified is usually unimportant:

         > ls -a -l
         > ls -l -a

both do exactly the same thing.

An parameter is an argument that is not an option. For example, in

         > cp --archive source dest

`cp` is called with three arguments, the option `--archive`, the parameter `source`, and the parameter `dest`. Unlike options, the order in which parameters are specified usually is important:

         > cp --archive --verbose source dest
         > cp --verbose --archive source dest
         > cp --archive source --verbose dest
         > cp --archive --verbose dest source

The first three `cp` commands do the same thing, but the fourth one is completely different.

If you're new to Gengetopt, you may wish to skip the rest of this section. It goes into more detail about different sorts of options, and how they are parsed.

Note that some parameters may begin with `-` or `--`. Equivalently, not all arguments that begin with `-` or `--` are options. Consider

         > ls -- -file
         > tar -c -f - . > ../foo.tar

The `ls` command has two arguments; the first argument, `--` is ignored by `ls`, but causes the `-file` argument to be interpreted as a parameter. The `tar` command has four arguments. The `-c` argument tells tar to create an archive; the `-f` argument, which takes a value, `-`, tells tar that the archive should be written onto the standard output, and the fourth argument, `.`, tells tar what directories to include in the archive. (The remaining two items, `>` and `../foo.tar`, tell the shell to redirect the `tar` command's output to the file ../foo.tar. The `tar` command doesn't even see them.)

The GNU convention is that `-` by itself is always interpreted as a value or parameter, while the first `--` by itself is always ignored, but causes all subsequent arguments to be interpreted as parameters. Gengetopt always behaves this way.

A short option is an option that begins with `-`. Not including the leading dash, short options must be one character long:

         > ls -a -l -t --width=80

The `-a`, `-l`, and `-t` options are all short options. Multiple short options may be combined into a single argument:

         > ls -alt --width=80

is equivalent to the above example.

A long option is an option that begins with `-` or `--`. Ignoring the leading punctuation, long options may be one or more characters long:

         > ls --all -fs

The `ls` command has two arguments; the long option `--all`, and the pair of short options `-fs`.

Long options need not have synonymous short options; after all, complex programs like `cc` have more long options than there are valid short option characters; it wouldn't be possible to assign a short option to each of them. Short options are encouraged, but not required, to have a synonymous long option.

Long options may be abbreviated, as long as the abbreviation is not ambiguous. Gengetopt automatically treats unambiguous abbreviations as synonyms.

Short options may have values just like long options, but if several short options are grouped together into one argument, only the last one may have a value. Values in the same argument as a long option are delimited by an equals sign, values in the same argument as a short option are not:

         > ls --width 60  # ok, value is "60"
         > ls --width=60  # ok, value is "60"
         > ls -w60        # ok, value is "60"
         > ls -w 60       # ok, value is "60"
         > ls -w=60       # unexpected, value is "=60"
         > ls -T7 -w60    # ok, value for -T is 7, value for -w is 60
         > ls -T7w60      # unexpected, value for -T is "7w60", no -w at all

A required option must be present, otherwise an error will be raised.

A multiple option is an option that may appear more than once on the command line. Gengetopt would create a tidy array for multiple options (see Multiple Options, for further details about dealing with multiple options).

Next: Group options, Previous: Terminology, Up: Top

## 5 Options with enumerated values

You can also specify the list of `values` that can be passed to an option (if the type is not specified, the option has type `string`). If a value that is not in the list is passed, an error is raised. You can think of such options as enumerated options. It is not necessary to pass the complete value at the command line option: a non ambiguous prefix will do. For instance, if the accepted values are `"foo","bar","foobar"`, then you can pass at the command line the value `"b"` and the value `"bar"` will be selected, or the value `"foob"` and the value `"foobar"` will be selected; instead, passing the value `"fo"` will raise an ambiguity error.

Since version 2.22 options with values can be given a specific type (the default is string). If you give a numeric type to such options, gengetopt will check that the enumerated values are actually valid values for that numeric type.

As for other options, the `<option>_arg` field will have the specified type, while the `<option>_orig` field will always be a string (`char *`) storing the (non-ambiguous) prefix specified at the command line.

For such an option, no matter what its type is, an array of strings, `<parser-name>_<option>_values`, will be generated that contains all the strings representing the possible accepted values.

An option with enumerated values can also be given the type `enum`; in that case, a C `enum` type is also generated with name `enum_<option>`; the values of such C enum will be generated according this pattern: `<option>_arg_<value>`, where `value` is the value specified in the input file, and the starting value is always 0. An additional value is generated to represent the null/empty value, with the pattern `<option>__NULL` (note the double underscore) with integer value -1. For instance, if we specify in the input file the following option

         option "myopt" ... ... values="FOO","180","BAR" enum ...

then the following C enum will be generated:

         enum enum_myopt {
         myopt__NULL = -1, myopt_arg_FOO = 0, myopt_arg_180, myopt_arg_BAR };

If you use the symbols `+` and `-`, these will be translated into `PLUS_` and `MINUS_`, respectively, in the C enum. Thus, if we specify in the input file the following option

         option "myopt" ... ... values="+foo","-all","-foo" enum ...

then the following C enum will be generated:

         enum enum_myopt { myopt__NULL = -1,
         	myopt_arg_PLUS_foo = 0,
         	myopt_arg_MINUS_all, myopt_arg_MINUS_foo };

An example using options with values (and enum options) is `tests/test_values_cmd.ggo` and `tests/test_values.c`.

Next: Mode options, Previous: Options with enumerated values, Up: Top

## 6 Group options

It is also possible to group options; options belonging to a group are considered in mutual exclusion. In order to use this feature, first the `group` has to be defined, and then a `groupoption` can be defined. A groupoption has basically the same syntax of a standard option, apart that the required flag must not be specified (it would not make sense, since the options of the same group are mutually exclusive) and the group to which the option belongs has to be specified.

         defgroup "<group name>" {groupdesc="<group description>"} {required}
         groupoption <long> <short> "<desc>" <argtype> group="<group name>" \
         	{argoptional} {multiple}

If a group is defined as `required`, then one (but only one) option belonging to the group has to be specified.

Here's an example (taken from the test `test_group_cmd.ggo`):

         defgroup "my grp2"
         defgroup "grp1" groupdesc="an option of this group is required" required
         groupoption "opta" a "string a" group="grp1" multiple
         groupoption "optA" A "string A" string group="grp1" argoptional
         groupoption "optAmul" M "string M" string group="grp1" argoptional multiple
         groupoption "optb" b "string b" group="grp1"
         groupoption "optc" - "string c" group="my grp2"
         groupoption "optd" d "string d" group="my grp2"

The group `grp1` is required, so either `--opta` or `--optb` has to be specified (but only one of them). Here's the output of some executions:

         $ ./test_groups
         test_groups: 0 options of group grp1 were given. One is required
         $ ./test_groups -a          OK
         $ ./test_groups -a -a       OK (the same option given twice)
         $ ./test_groups -a -b
         test_groups: 2 options of group grp1 were given. One is required
         $ ./test_groups -a -c       OK
         $ ./test_groups -a --optc -d
         test_groups: 2 options of group my grp2 were given. At most one is required

Next: Parser function additional parameters, Previous: Group options, Up: Top

## 7 Mode options

It is also possible to specify “mode options”; options belonging to a mode are considered in mutual exclusion with options of a different mode. Thus, you can specify more options belonging to the same mode, but you cannot specify, on the same command line, two options belonging to two different modes (thus, modes are different from groups, Group options).

These sets of options are called modes, since they represent the different modes (modalities), in which a program can be run.

In order to use this feature, first the `mode` has to be defined, and then a `modeoption` can be defined. A modeoption has basically the same syntax of a standard option, and it can be given the required flag must not be specified (with a slightly different semantics, see below) and the group to which the option belongs has to be specified.

         defmode "<mode name>" {modedesc="<mode description>"}
         modeoption <long> <short> "<desc>" <argtype> mode="<mode name>" \
         	{argoptional} {multiple} {required}

If a mode option is specified as `required`, then it will be required only if other options of the same mode are specified; this makes it possible to specify options of different modes as required.

Options not belonging to any mode are not in conflict with mode options.

For instance, let us consider the file `test_modes_cmd.ggo`:

         package "test_modes"
         version "1.0"

         section "some non mode options"

         option "no-mode" N "a generic option not beloging to any mode" optional
         option "no-mode2" - "another generic option not beloging to any mode" string optional

         section "some modes just for testing"

         defmode "mode 2"
         defmode "my mode"
         defmode "mode1" modedesc="any option of this mode is in contrast with any \
         option of the other mode\nNotice that this description is quite long so \
         it may spawn many lines...              \
         fortunately gengetopt will wrap it for you :-)"

         modeoption "opta" a "string a" multiple mode="mode1" optional
         modeoption "optA" A "string A" string argoptional mode="mode1" required
         modeoption "optAmul" M "string M"
                 argoptional string mode="mode1" multiple optional
         modeoption "optb" b "string b" mode="mode1" optional

         modeoption "optc" - "string c" mode="mode 2" optional
         modeoption "optd" d "string d" mode="mode 2" required

         modeoption "mopt" m "option of my mode" int optional mode="my mode" optional

Now, we use the program `test_modes` (that uses the generated parser for the input file above) to demonstrate how the parser generated by gengetopt perform checks on mode options.

         test_modes -N

This execution generates no errors (although there are required options which are not specified, these required options are part of modes and they are required only if that mode is used).

         test_modes -a
         ./test_modes: '--optA' ('-A') option required

Since an option of a mode is specified, then required options of that mode must be provided, but, in this execution, we forgot to specify a required option of the mode that is being used.

         test_modes -a -A -N

This execution is correct: we specified two options of the same mode, in particular we also specified the required option of that mode. Notice that we use also an option not belonging to any mode, which does not interfere with mode options.

         test_modes -a -A -N --optc
         test_modes: option --optc conflicts with option --opta
         test_modes: option --optc conflicts with option --optA
         test_modes: '--optd' ('-d') option required

Here we see a conflict, (actually two), since the last option we specified belongs to a mode that is different from the one of the first two options.

If you require gengetopt to generate `--full-help` (See `--full-help`.), the usage string will be generated so that it will show the modes of the program; for instance, this is the output of `--help` of the generated parser for the input file above:

         test_modes 1.0

         Usage: test_modes [-h|--help] [-V|--version] [-N|--no-mode] [--no-mode2=STRING]
           or : test_modes -d|--optd [--optc]
           or : test_modes -ASTRING|--optA=STRING [-a|--opta]
                  [-MSTRING|--optAmul=STRING] [-b|--optb]
           or : test_modes [-mINT|--mopt=INT]

           -h, --help              Print help and exit
           -V, --version           Print version and exit

         some non mode options:
           -N, --no-mode           a generic option not beloging to any mode
               --no-mode2=STRING   another generic option not beloging to any mode

         some modes just for testing:

          Mode: mode1
           any option of this mode is in contrast with any option of the other mode
           Notice that this description is quite long so it may spawn many lines...
           fortunately gengetopt will wrap it for you :-)
           -a, --opta              string a
           -A, --optA[=STRING]     string A
           -M, --optAmul[=STRING]  string M
           -b, --optb              string b

          Mode: mode 2
               --optc              string c
           -d, --optd              string d

          Mode: my mode
           -m, --mopt=INT          option of my mode

Next: Configuration files, Previous: Mode options, Up: Top

## 8 Parser function additional parameters

Besides the parser functions, in the generated header file, gengetopt also generates31 an additional structure `<cmd_parser_name>_params` that can be used to customize the invocation of the generated parsers (it is especially useful when using configuration file parsers, Configuration files, string parsers, String Parsers and Multiple Parsers, and, in general, multiple parsers).

These are the fields of this structure (as usual, boolean options are represented as `int` and they are `true` if they are set to `1` and `false` if they are set to `0`):

`int initialize (default = 1)`
  tells whether the args_info struct has to be initialized.
`int override (default = 0)`
  tells whether the values for the options that are parsed should override those that are already present in the passed args_info struct (e.g., this is the case when you call a parser multiple times using the same args_info struct, see, e.g., Configuration files and String Parsers and Multiple Parsers).
`int check_required (default = 1)`
  tells whether the check for required options must be performed or not.
`int check_ambiguity (default = 0)`
  tells whether the check whether options that are parsed are not already present in the passed args_info struct; this is performed only for NON multiple options (see also Multiple Options).
`int print_errors (default = 1)`
  tells32 whether `getopt_long` must print error messages to the standard error stream if it encounters an unknown option character or an option with a missing required argument. This is the default behavior. If you set this variable to zero, `getopt_long` does not print any messages, but the generated parser will still return with error.

Gengetopt also generates an initialization function for such structures33, called `<cmd_parser_name>_params_init`, which takes as argument a pointer to such structure and initialize all its fields to their default values; it also generates a function called `<cmd_parser_name>_params_create` that returns a dynamically allocated structure with all fields initialized to their default values.

We strongly advise to use such functions for creating and initializing such a structure, since this will make your code scalable to future releases of gengetopt where such structure might contain additional fields. Otherwise, you might risk to use a structure where some fields are not initialized, with unpredictable results. Furthermore, since the `<cmd_parser_name>_params_create` function returns a pointer to a dynamically allocated structure (with `malloc`), it is up to you to deallocate that structure when you no longer need it (with `free`).

Some examples of usage of this parameters struct are shown in Configuration files.

Next: Multiple Options, Previous: Parser function additional parameters, Up: Top

## 9 Configuration files

It is often useful to specify command line options directly in a configuration file, so that the value of some options are read from this file if they are not given as command line options. When the command line option `-C|--conf-parser` is given to gengetopt, apart from the standard command line option parser, also this additional parser is generated (its name is `<cmd_parser_name>_config_file`34):

         int
         <cmd_parser_name>_config_file(char * const filename,
         	struct gengetopt_args_info *args_info,
         	struct <cmd_parser_name>_params *params);

The parameter structure `<cmd_parser_name>_params` is described in Parser function additional parameters. For instance, `params->override` tells whether the values read in the configuration file have to override those specified at the command line.

IMPORTANT: you have to explicitly set `params->initialize` to 1 if you call the config file parser before the standard command line option parser, otherwise unpredictable results may show.

If you call the config file parser before the standard command line option parser and then you want to call the standard command line parser you MUST use this second version of the parser function, with `params->initialize` set to 0, so that collected values from the config file are not lost35:

         int
         <cmd_parser_name>_ext (int argc,
         	char **argv,
         	struct gengetopt_args_info *args_info,
         	struct <cmd_parser_name>_params *params);

Notice, that with this version you can also specify whether the options passed at the command line must override the ones read from the config file. Moreover, you have to specify whether the check for missing required options must be performed or not. This concerns also options of a required group (Group options).

If you decide not to request the check for required option, you can test it manually, after the command line parsing returns by using the following generated function:

         int
         <cmd_parser_name>_required (struct gengetopt_args_info *args_info,
         	const char *program_name);

where `program_name` is the name of your executable (usually you should pass `argv[0]` as argument). If the function returns a value different from 0, then some required options are missing. An error has already been printed by this function. This concerns also options of a required group (Group options).

The config file has the following simple syntax: lines starting with `#` are considered comments and:

         <option_name> = {<option_val>}

or simply (if the option does not take an argument):

         <option_name>

which means that `option_name` is given, and if it accepts an argument, then its value is `option_val`. The `=` is not mandatory.

Since version 2.19, it is possible to include other files (i.e., other configuration files) in a configuration file, by using the `include` syntax:

         include "filename"

For instance here's a program that uses this feature (this is the test `test_conf_parser`):

         /* test_conf_parser.c test */

         /* test all kinds of options and the conf file parser */

         #ifdef HAVE_CONFIG_H
         #include "config.h"
         #endif

         #include <stdlib.h>
         #include <stdio.h>

         #include "test_conf_parser_cmd.h"

         static struct my_args_info args_info;

         int
         main (int argc, char **argv)
         {
           unsigned int i;
           int result = 0;

           struct test_conf_parser_cmd_parser_params *params;

           /* initialize the parameters structure */
           params = test_conf_parser_cmd_parser_params_create();

           /* call the command line parser */
           if (test_conf_parser_cmd_parser (argc, argv, &args_info) != 0) {
             result = 1;
             goto stop;
           }

           /*
              override command line options,
              but do not initialize args_info, check for required options.
              NOTICE: we must NOT skip the 0 assignment to initialize,
              since its default value is 1 and override defaults to 0
              while check_required is already set to its default value, 1
           */
           params->initialize = 0;
           params->override = 1;

           /* call the config file parser */
           if (test_conf_parser_cmd_parser_config_file
               (args_info.conf_file_arg, &args_info, params) != 0)
             {
               result = 1;
               goto stop;
             }

           printf ("value of required: %s\n", args_info.required_arg);
           printf ("value of string: %s\n", args_info.string_arg);
           printf ("value of no-short_given: %d\n", args_info.no_short_given);
           printf ("value of int: %d\n", args_info.int_arg);
           printf ("value of float: %f\n", args_info.float_arg);

           printf ("value of multi-string_given: %d\n", args_info.multi_string_given);
           for (i = 0; i < args_info.multi_string_given; i++)
             printf ("  value of multi-string: %s\n", args_info.multi_string_arg [i]);

           printf ("value of multi-string-def_given: %d\n",
                   args_info.multi_string_def_given);
           for (i = 0; i < args_info.multi_string_def_given; ++i)
             printf ("  value of multi-string-def: %s\n",
                     args_info.multi_string_def_arg [i]);
           if (!args_info.multi_string_def_given && args_info.multi_string_def_arg [0])
             printf ("default value of multi-string-def: %s\n",
                     args_info.multi_string_def_arg [0]);

           printf ("value of opta: %s\n", args_info.opta_arg);

           printf ("noarg given %d times\n", args_info.noarg_given);
           printf ("noarg_noshort given %d times\n", args_info.noarg_noshort_given);

           printf ("opt-arg given: %d\n", args_info.opt_arg_given);
           printf ("opt-arg value: %s\n", (args_info.opt_arg_arg ? args_info.opt_arg_arg : "not given"));

           if (args_info.file_save_given) {
             if (test_conf_parser_cmd_parser_file_save (args_info.file_save_arg, &args_info) == EXIT_FAILURE)
               result = 1;
             else
               printf ("saved configuration file %s\n", args_info.file_save_arg);
           }

          stop:
           /* deallocate structures */
           test_conf_parser_cmd_parser_free (&args_info);
           free (params);

           return result;
         }

So if we use the following config file

         # required option
         required "this is a test"
         float 3.14
         no-short
         string another

and we run `test_conf_parser` like that, we will have

         ./test_conf_parser -r bar -i 100 --float 2.14 --conf-file test_conf.conf
         value of required: this is a test
         value of string: another
         value of no-short: 1
         value of int: 100
         value of float: 3.140000

If, instead we call the `test_conf_parser_cmd_parser_configfile` with 0 for override argument, we get the following result

         value of required: bar
         value of string: another
         value of no-short: 1
         value of int: 100
         value of float: 2.140000

This second example use the second version of the command line parser: first call the configuration file parser and then the command line parser (the command line options will override the configuration file options):

         /* test_conf_parser_ov2.c test */

         /* test all kinds of options and the conf file parser */
         /* differently from test_conf_parser_ov.c, first scan the conf file and
            then the command line */

         #ifdef HAVE_CONFIG_H
         #include "config.h"
         #endif

         #include <stdlib.h>
         #include <stdio.h>

         #include "test_conf_parser_cmd.h"

         static struct my_args_info args_info;

         int
         main (int argc, char **argv)
         {
           struct test_conf_parser_cmd_parser_params *params;

           /* initialize the parameters structure */
           params = test_conf_parser_cmd_parser_params_create();

           /*
              initialize args_info, but don't check for required options
              NOTICE: the other fields are initialized to their default values
           */
           params->check_required = 0;

           /* call the config file parser */
           if (test_conf_parser_cmd_parser_config_file
               ("./test_conf2.conf", &args_info, params) != 0)
             exit(1);

           /*
              override config file options,
              do not initialize args_info, check for required options.
           */
           params->initialize = 0;
           params->override = 1;
           params->check_required = 1;

           /* call the command line parser */
           if (test_conf_parser_cmd_parser_ext (argc, argv, &args_info, params) != 0)
             exit(1) ;

           printf ("value of required: %s\n", args_info.required_arg);
           printf ("value of string: %s\n", args_info.string_arg);
           printf ("value of no-short_given: %d\n", args_info.no_short_given);
           printf ("value of int: %d\n", args_info.int_arg);
           printf ("value of float: %f\n", args_info.float_arg);

           /* release memory */
           test_conf_parser_cmd_parser_free (&args_info);
           free (params);

           return 0;
         }

This is an invocation and its results:

         ./test_conf_parser_ov2 -r "bar" --float 2.14 -i 100
         value of required: bar
         value of string: another
         value of no-short: 1
         value of int: 100
         value of float: 2.140000

If on the above code you substitute `params->override = 1` with `params->check_ambiguity = 1` (see the test file `test_conf_parser_ov4.c`), then the following invocation will generate an error:

         ./test_conf_parser_ov4 -r "bar" -i 100
         ./test_conf_parser_ov4: `--required' (`-r') option given more than once

since the `-r` option is specified both in the configuration file and at the command line.

### 9.1 Further details on the configuration file parser

The generated config file parser function uses the constant `CONFIG_FILE_LINE_SIZE` to read each line of the configuration file. By default this constant is set to `2048` that should be enough for most applications. If your application uses configuration files with lines that are longer, you can compile the generated C file by specifying an explicit value for this constant with the `-D` command line option of `gcc`.

Next: String Parsers and Multiple Parsers, Previous: Configuration files, Up: Top

## 10 Multiple Options

If an option is specified as `multiple`, then it can be specified multiple times at command line. In this case, say the option is called `foo`, the generated `foo_given` field in the args structure contains the number of times it was specified and the generated field `foo_arg` is an array containing all the values that were specified for this option.

Notice that if a default value is specified for a multiple option, that value is assigned to the option only if no other value is specified on the command line, i.e., a default value IS NOT always part of the values of a multiple option.

As in the case for standard options, if a multiple option has a default value, and this is set because no value was specified on the command line, then the corresponding `<option>_given` will still be initialized to 0. Thus, `<option>_given` will effectively inform you if the user has specified that command line option.

If it is known that a multiple option has a default value, then it can be safely assumed that the first element of generated array `<option>_arg` is always set.

For instance, if the gengetopt file is as follows

         # test options that can be given more than once
         option "string"      s "string option" string optional multiple
         option "int"         i "int option" int optional multiple

Then the command line options can be collected like that

         /* test options that can be given more than once */

         #ifdef HAVE_CONFIG_H
         #include "config.h"
         #endif

         #include <stdlib.h>
         #include <stdio.h>

         #include "test_multiple_cmd.h"

         static struct gengetopt_args_info args_info;

         int
         main (int argc, char **argv)
         {
           int i = 0;

           if (test_multiple_cmd_parser (argc, argv, &args_info) != 0)
             exit(1) ;

           for (i = 0; i < args_info.string_given; ++i)
             printf ("passed string: %s\n", args_info.string_arg[i]);

           for (i = 0; i < args_info.int_given; ++i)
             printf ("passed int: %d\n", args_info.int_arg[i]);

           return 0;
         }

Then if this program is called with the following command line options

         ./multiple_example -s world -s hellow -s bar -s foo -i 200 -i 100

The output of the program will be

         passed string: world
         passed string: hello
         passed string: bar
         passed string: foo
         passed int: 200
         passed int: 100

You can also pass arguments to a multiple option separated by commas (if you need to actually specify the comma operator as part of the argument you can escape it with `\`), as in the following:

         ./test_multiple -s"foo","bar","hello" -i100,200 -s "world"

You can specify the number of occurrences of multiple options by using the following syntax (that must be given after the `multiple` keyword):

`(number)`
  requires that the multiple option, if given, must be given exactly `number` times
`(number1-number2)`
  requires that the multiple option, if given, must be given not less than `number1` times and no more than `number2` times
`(number-)`
  requires that the multiple option, if given, must be given at least `number` times
`(-number)`
  requires that the multiple option, if given, must be given at most `number` times

Here are some examples:

         option "string"      s "string option" string optional multiple(4)

         option "string"      s "string option" string optional multiple(1-4)

         option "string"      s "string option" string optional multiple(-5)

Notice that this is independent from the `required` flag.

Next: No getopt_long, Previous: Multiple Options, Up: Top

## 11 String Parsers and Multiple Parsers

The parsers generated by gengetopt (indeed the C and header files) are self-contained and different parsers can be linked in the same program, without interferences. This is useful, e.g., in cases where a specific command line option argument has a complex syntax that accepts options itself according to terminology already defined, i.e., the one handled by `getopt_long`, see Terminology. Another case when multiple parsers can be useful is when your command behaves differently according to a specific command line option.

Obviously there exists only one instance of command line arguments passed to the `main` function (namely the variables `argc` and `argv`) so passing the same arguments to different command line parsers is likely to generate errors: the different command line parsers are likely to have different syntaxes for accepted options.

For this reason gengetopt can generate parser functions that take a string containing the further options to parse, instead of taking an array. This additional parser will have the parser name and the suffix `_string`. If you want these additional parsers to be generated you have to pass the command line option `-S|--string-parser` to gengetopt (see Invoking gengetopt). The two functions will be:

         int <parser_name>_string (const char *cmdline,
         	struct test_first_cmdline_cmd_struct *args_info,
         	const char *prog_name);
         int <parser_name>_string_ext (const char *cmdline,
         	struct test_first_cmdline_cmd_struct *args_info,
         	const char *prog_name,
         	struct <cmd_parser_name>_params *params);

The second version36 allows you to specify more details about the parsing, using the `<cmd_parser_name>_params` structure, shown in Parser function additional parameters (this is the same as for configuration files, thus we refer to that section for the details of the two functions and default values, see Configuration files).

Of course, these functions can be used in general to simulate the invocation of a program with specific command line options (stored in the first string argument), or in general to parse options that are all stored in a string (instead of a vector).

The first argument of these parsers is a string containing the options to parse (remember that this must respect the option format handled by `getopt_long`, see Terminology). The second one is the pointer to the struct that will be filled with passed options and arguments, as usual. The third option is the program name: this will be used when errors have to be printed. This last argument can be null: in this case, the first element of the first string argument is considered the program name.

Let's show these functionalities with an example. Consider a program that accepts two command line options (required in this case):

         # test for multiple parsers, this is the main file
         # test_main_cmdline_cmd.ggo

         option "first-cmd" F "the first command line to parse" required \
         	typestr="first command" string multiple
         option "second-cmd" S "the second command line to parse" required \
         	typestr="second command" string multiple

These two options accept strings as argument that in turn are considered command line arguments, according to specific syntaxes. The first one is:

         # test for multiple parsers, this is the first command line file
         # test_first_cmdline_cmd.ggostr

         option "option-a" a "option a of the first command line to parse"
         optional int option "multi" M \
         	"multiple option of the first command line to parse" \
         	optional string multiple

and the second one is:

         # test for multiple parsers, this is the second command line file
         # test_second_cmdline_cmd.ggostr

         option "option-a" a "option a of the second command line to parse" \
         	optional string
         option "option-b" b "option a of the second command line to parse" \
         	optional string
         option "my-multi" M \
         	"multiple option of the second command line to parse" \
         	optional string multiple

These last two files are processed with gengetopt using the `--string-parser`. Let's put everything together in this main file:

         #ifdef HAVE_CONFIG_H
         #include "config.h"
         #endif

         #include <stdio.h>
         #include <stdlib.h>

         #include "test_main_cmdline_cmd.h"
         #include "test_first_cmdline_cmd.h"
         #include "test_second_cmdline_cmd.h"

         int
         main(int argc, char **argv)
         {
           struct gengetopt_args_info main_args_info;
           struct test_first_cmdline_cmd_struct first_args_info;
           struct test_second_cmdline_cmd_struct second_args_info;
           int exit_code = 0;
           unsigned int i, j;

           if (test_main_cmdline_cmd_parser (argc, argv, &main_args_info) != 0) {
             exit_code = 1;
             return exit_code;
           }

           for (j = 0; j < main_args_info.second_cmd_given; ++j) {
             printf("second cmdline: %s\n", main_args_info.second_cmd_arg[j]);
             if (test_second_cmdline_cmd_parser_string
         	(main_args_info.second_cmd_arg[j], &second_args_info, argv[0]) == 0) {
               if (second_args_info.option_a_given)
         	printf("  --option-a: %s\n", second_args_info.option_a_arg);
               if (second_args_info.option_b_given)
         	printf("  --option-b: %s\n", second_args_info.option_b_arg);
               for (i = 0; i < second_args_info.my_multi_given; ++i)
         	printf("  --my-multi: %s\n", second_args_info.my_multi_arg[i]);

               test_second_cmdline_cmd_parser_free (&second_args_info);
             }
           }

           for (j = 0; j < main_args_info.first_cmd_given; ++j) {
             printf("first cmdline: %s\n", main_args_info.first_cmd_arg[j]);
             if (test_first_cmdline_cmd_parser_string
         	(main_args_info.first_cmd_arg[j], &first_args_info, argv[0]) == 0) {
               if (first_args_info.option_a_given)
         	printf("  --option-a: %d\n", first_args_info.option_a_arg);
               for (i = 0; i < first_args_info.multi_given; ++i)
         	printf("  --multi: %s\n", first_args_info.multi_arg[i]);

               test_first_cmdline_cmd_parser_free (&first_args_info);
             }
           }

           test_main_cmdline_cmd_parser_free (&main_args_info);

           return exit_code;
         }

Notice that in the `for` loops we always free the elements of the argument structures in order to avoid memory leaks.

Now if you can run this program as follows (notice that we use the comma separated arguments for multiple option arguments but we escape it with `\` because otherwise, e.g., 200 and 300 would be intended as further arguments of `--first-cmd` instead of `--multi`, see Multiple Options):

         ./test_multiple_parsers \
         	--first-cmd="-M400 -a10 --multi 100\,200\,300" \
         	--second-cmd="-a20 -b10 --my-multi=a\,b\,c\,d\,e\,f" \
         	-F"-M500 -M600" -S"--my-multi g"
         second cmdline: -a20 -b10 --my-multi=a,b,c,d,e,f
         	--option-a: 20
         	--option-b: 10
         	--my-multi: a
         	--my-multi: b
         	--my-multi: c
         	--my-multi: d
         	--my-multi: e
         	--my-multi: f
         second cmdline: --my-multi g
         	--my-multi: g
         first cmdline: -M400 -a10 --multi 100,200,300
         	--option-a: 10
         	--multi: 400
         	--multi: 100
         	--multi: 200
         	--multi: 300
         first cmdline: -M500 -M600
         	--multi: 500
         	--multi: 600

Next: Bugs, Previous: String Parsers and Multiple Parsers, Up: Top

## 12 What if getopt_long is not available?

If you use gengetopt to generate C functions for parsing command line arguments you have to know that these generated functions use `getopt_long` to actually read the command line and parsing it. This function is typically part of the standard C library, but some implementations may not include it. If you want your program to be portable on several systems, and be compilable with many C compilers, you can rely on one of the following solutions.

Next: Use automake/autoconf, Previous: No getopt_long, Up: No getopt_long

### 12.1 Include the `getopt_long` code into the generated parser

Since version 2.17, gengetopt can include into the generated C parser file the code of `getopt_long`, so that the include code will be used to actually parse the command line arguments, instead of that taken from the C library.

This solution is actually quite easy, since you only need to specify the command line option `--include-getopt` (see Invoking gengetopt), but it has two main drawbacks:

- The generate C file of the parser will be much bigger;
- You won't be able to use the latest version of `getopt_long` of the C library

It is up to you to choose between this and the automake/autoconf based solution.

Actually, this solution has the advantage that your program won't behave strangely when used with another implementation of `getopt_long`.

I prefer the automake/autoconf based solution, as described in Use automake/autoconf, in particular the one described in Use Gnulib, which is also the one I adopt for gengetopt itself.

Previous: Include the getopt_long code into the parser, Up: No getopt_long

### 12.2 Use automake/autoconf to check for the existence of `getopt_long`

Autoconf and Automake are great tools to generate a configure script that automatically checks for the configuration of your system and for possible missing functions required to compile your program. However, in case of detected missing functions, your program must be able to provide a replacement for such functions. In the next sections we describe two mechanisms for including the (possible) missing code for `getopt_long` and for checking its presence with automake/autoconf. Since version 2.19, gengetopt itself uses the first mechanism.

Next: Use getopt_long sources, Previous: Use automake/autoconf, Up: Use automake/autoconf

#### 12.2.1 Use Gnulib

Since version 2.19 I also started to use Gnulib - The GNU Portability Library37, “a central location for common GNU code, intended to be shared among GNU packages”. Gnulib provides an easy and smooth way to add to your package sources the sources of functions that you want to check during configure. It will also handle the checks for these functions in the configure script, and in case they're not in your system (or they're present but with some missing features) it compiles their sources into a library (that you will need to link your program to, as illustrated in the following).

Once you retrieved gnulib (for the moment it is available only through git, see the home page), you can invoke ``gnulib-tool --import`' that will copy source files, create a `Makefile.am` to build them, generate a file `gnulib-comp.m4` with Autoconf M4 macro declarations used by `configure.ac`, and generate a file `gnulib-cache.m4` containing the cached specification of how Gnulib is used. In particular, you must specify the modules you want to import, and in our case, it is getopt:

         gnulib-tool --import getopt

By default, the source code is copied into `lib/` and the M4 macros in `m4/`. You can override these paths by using `--source-base=DIRECTORY` and `--m4-base=DIRECTORY`. For instance, gengetopt uses `gl` and `gl/m4`, respectively. We will use these directories in the rest of this section.

You must ensure Autoconf can find the macro definitions in `gnulib-comp.m4`. Use the `ACLOCAL_AMFLAGS` specifier in your top-level `Makefile.am` file (and the first time you run `aclocal` you have to use the `-I` as well); for instance, in the case of gengetopt we have:

         ACLOCAL_AMFLAGS = -I gl/m4

You are now ready to call the M4 macros in `gnulib-comp.m4` from `configure.ac`. The macro `gl_EARLY` must be called as soon as possible after verifying that the C compiler is working. Typically, this is immediately after `AC_PROG_CC`, as in:

         ...
         AC_PROG_CC
         gl_EARLY
         ...

The core part of the gnulib checks are done by the macro `gl_INIT`. Place it further down in the file, typically where you normally check for header files or functions. For example:

         ...
         # For gnulib.
         gl_INIT
         ...

`gl_INIT` will in turn call the macros related with the gnulib functions, be it specific gnulib macros. So there is no need to call those macros yourself when you use the corresponding gnulib modules.

You must also make sure that the gnulib library is built. Add the `Makefile` in the gnulib source base directory to `AC_CONFIG_FILES`, as in:

         AC_CONFIG_FILES(... gl/Makefile ...)

You must also make sure that `make` will recurse into the gnulib directory. To achieve this, add the gnulib source base directory to a `SUBDIRS` Makefile.am statement, as in:

         SUBDIRS = gl

Finally, you have to add compiler and linker flags in the appropriate source directories, so that you can make use of the gnulib library. Since the ``getopt`' module copies files into the build directory, `top_builddir/gl` is needed as well as `top_srcdir/gl`. For example:

         ...
         AM_CPPFLAGS = -I$(top_srcdir)/gl -I$(top_builddir)/gl
         ...
         LDADD = gl/libgnu.a
         ...

Don't forget to `#include` the various header files. In this example, you would need to make sure that ``#include "getopt.h"`' is evaluated when compiling all source code files, that want to make use of `getopt` or `getopt_long`. If you simply use the files generated by gengetopt, you won't need include this header though, since it is already handled by the generated files.

Every now and then, check whether there are updates in the Gnulib modules, and if the modules you use (e.g., `getopt`) are upgraded, please remember to also update your files, simply by running:

         gnulib-tool --update

We refer to Gnulib documentation for further explanations and features.

Previous: Use Gnulib, Up: Use automake/autoconf

#### 12.2.2 Use getopt_long sources

NOTICE: this was the procedure used by gengetopt itself up to version 2.18. We suggest now to use the procedure described in Use Gnulib, since the files described in the following might not be kept up-to-date.

We provide C files that actually implement `getopt_long` function: `getopt.c` `getopt1.c` and `gnugetopt.h`. You'll find these files in the `<install prefix>/share/gengetopt` directory where `<install prefix>` is the one you specified during compilation. If no prefix had been specified, `/usr/local` is the default. If you downloaded gengetopt in binary form prefix will probably be `/usr/local` or `/usr`.

You can rename `gnugetopt.h` to `getopt.h` and then simply compile these files and link them to the executable of you program. However, if you use automake and autoconf here's a more elegant solution: you should download the file `adl_func_getopt_long.m4` you find at this site:

https://autoconf-archive.cryp.to

and add its contents to your `acinclude.m4`. You can find this macro also in the `acinclude.m4` in the sources of gengetopt.

This macro checks if getopt_long function is in C library; if it is not then it adds `getopt.o` and `getopt1.o` to the objects files that will be linked to your executable (`LIBOBJS`).

Then in `Makefile.am` of your source directory you have to add the contents of `LIBOBJS` to the `LDADD` of the program that has to use getopt_long; e.g., if the program `foo` has to use getopt_long, you have to add the following line

         foo_LDADD = @LIBOBJS@

Now these files will be compiled and linked to your program only if necessary.

Moreover you have to add `getopt.c` `getopt1.c` and `gnugetopt.h` to your distribution. Note that it is not necessary to put these file names among the `foo_SOURCES` contents), but you have to add `gnugetopt.h` to `EXTRA_DIST`:

         EXTRA_DIST = gnugetopt.h

You may want to take a look at gengetopt's `configure.in` and `src/Makefile.am`: they both use the techniques described here.

Next: Mailing Lists, Previous: No getopt_long, Up: Top

## 13 Known Bugs and Limitations

If you find a bug in `gengetopt`, please use the Savannah web interface

https://savannah.gnu.org/bugs/?group=gengetopt

Include the version number, which you can find by running ``gengetopt --version`'. Also include in your message the output that the program produced and the output you expected.

If you have other questions, comments or suggestions about `gengetopt`, contact the author via electronic mail or ask at the mailing list.

The list of to-dos in the `TODO`.

Previous: Bugs, Up: Bugs

### 13.1 Getopt and subsequent calls

It seems that `getopt_long`, at least the version in the GNU library, if invoked with different `argv` arrays, might access memory in a bad way leading to crashes or unexpected behaviors. This happens because it keeps pointers to locations of the previous arrays if not initialized each time by setting `optind = 0`38. Unfortunately this initialization behavior seems to be part only of the implementation of GNU library and actually it is not documented (you can see it by taking a look into the source of `getopt.c`); other implementations of `getopt_long` might not be affected by this problem; alternatively, as reported by a user, `optind = 0` leads some `getopt_long` implementations to consider the program name as a command line option (since it is in position 0), which is bad anyway!

Probably this is usually not a problem since you usually parse only the command line, thus you only invoke the command line parser only once, and only with one instance of array (i.e., the `argv` passed to `main`). However, it can lead to problems when you use advanced features, as in the case of configuration file parsing (see Configuration files) and multiple parsers (see String Parsers and Multiple Parsers).

The parser generated by gengetopt checks whether the program name was actually considered a command line option, and in that case it removes it from the collected command line options; thus, this `optind` issue should not come up anyway. In case you still don't feel comfortable, you can include a correct `getopt_long` implementation in the generated parser, so that you can be sure you will always use the same implementation of `getopt_long` (Include the getopt_long code into the parser).

Next: Index, Previous: Bugs, Up: Top

## 14 Mailing Lists

The following mailing lists are available:

`help-gengetopt at gnu dot org`

for generic discussions about the program and for asking for help about it (open mailing list), https://mail.gnu.org/mailman/listinfo/help-gengetopt

`info-gengetopt at gnu dot org`

for receiving information about new releases and features (read-only mailing list), https://mail.gnu.org/mailman/listinfo/info-gengetopt.

`bug-gengetopt at gnu dot org`

if you prefer reporting bugs via email instead of web interface at savannah, please use this mailing list, https://mail.gnu.org/mailman/listinfo/bug-gengetopt.

If you want to subscribe to a mailing list just go to the URL and follow the instructions, or send me an e-mail and I'll subscribe you.

Previous: Mailing Lists, Up: Top

## Index

- `--arg-struct-name`: Invoking gengetopt
- `--conf-parser`: Invoking gengetopt
- `--default-optional`: Basic Usage
- `--default-optional`: Invoking gengetopt
- `--detailed-help`: Basic Usage
- `--full-help`: Basic Usage
- `--func-name`: Invoking gengetopt
- `--gen-version`: Invoking gengetopt
- `--header-output-dir`: Invoking gengetopt
- `--include-getopt`: Include the getopt_long code into the parser
- `--include-getopt`: Invoking gengetopt
- `--long-help`: Invoking gengetopt
- `--no-handle-error`: Invoking gengetopt
- `--no-handle-help`: Invoking gengetopt
- `--no-handle-version`: Invoking gengetopt
- `--no-help`: Invoking gengetopt
- `--no-version`: Invoking gengetopt
- `--output-dir`: Invoking gengetopt
- `--show-full-help`: Invoking gengetopt
- `--show-help`: Invoking gengetopt
- `--show-required`: Invoking gengetopt
- `--show-version`: Invoking gengetopt
- `--src-output-dir`: Invoking gengetopt
- `--string-parser`: Invoking gengetopt
- `--unnamed-opts`: Invoking gengetopt
- `-C,--conf-parser`: Configuration files
- `-h,--detailed-help`: Basic Usage
- `-h,--help`: Basic Usage
- `-S,--string-parser`: String Parsers and Multiple Parsers
- `-V,--version`: Basic Usage
- <cmd_parser_name>_config_file: Configuration files
- <cmd_parser_name>_ext: Configuration files
- <cmd_parser_name>_required: Configuration files
- argoptional: Basic Usage
- args: Basic Usage
- argtype: Basic Usage
- argument, defined: Terminology
- argv: Basic Usage
- Audience: Audience
- autoconf: Installation
- autoconf: Use getopt_long sources
- autoconf: Use automake/autoconf
- autoconf: Installation
- automake: Installation
- automake: Use getopt_long sources
- automake: Use automake/autoconf
- automake: Installation
- check_ambiguity: Parser function additional parameters
- check_required: Parser function additional parameters
- Conditions for copying Gengetopt: Copying
- configuration files: Configuration files
- Copying conditions: Copying
- default: Basic Usage
- dependon: Basic Usage
- desc: Basic Usage
- description: Basic Usage
- details: Basic Usage
- download: Installation
- enum: Options with enumerated values
- enumerated options: Options with enumerated values
- gengetopt options: Invoking gengetopt
- getopt_long: No getopt_long
- getting started with Gengetopt: Basic Usage
- Git: Installation
- gnulib: Use Gnulib
- gnulib: Installation
- group options: Group options
- hidden: Basic Usage
- how to use Gengetopt: Basic Usage
- include: Configuration files
- initialize: Parser function additional parameters
- installation: Installation
- invoking: Invoking gengetopt
- Known Bugs: Bugs
- libtool: Installation
- Limits: Bugs
- long: Basic Usage
- long option, defined: Terminology
- mailing list: Mailing Lists
- Misfeatures: Bugs
- mode options: Mode options
- multiple: Basic Usage
- multiple option, defined: Terminology
- multiple options: Multiple Options
- multiple parsers: String Parsers and Multiple Parsers
- on/off: Basic Usage
- option without name: Basic Usage
- option, defined: Terminology
- optional: Basic Usage
- override: Parser function additional parameters
- PACKAGE: Basic Usage
- PACKAGE: Audience
- package: Basic Usage
- PACKAGE_NAME: Audience
- PACKAGE_NAME: Basic Usage
- parameter: Basic Usage
- parameter, defined: Terminology
- parameters: Parser function additional parameters
- parser parameters: Parser function additional parameters
- print_errors: Parser function additional parameters
- purpose: Basic Usage
- required: Basic Usage
- required option, defined: Terminology
- requirements: Installation
- section: Basic Usage
- short: Basic Usage
- short option, defined: Terminology
- string parsers: String Parsers and Multiple Parsers
- Terminology: Terminology
- text: Basic Usage
- tutorial: Basic Usage
- typestr: Basic Usage
- usage: Basic Usage
- value, defined: Terminology
- values: Basic Usage
- values: Options with enumerated values
- version: Basic Usage
- VERSION: Basic Usage
- VERSION: Audience
- versiontext: Basic Usage
- Who should use Gengetopt: Audience
- wrapping: Basic Usage

#### Footnotes

[1] Since version 2.22.4 of Gengetopt the CVS repository was dismissed in favor of Git (https://git-scm.com/).

[2] https://www.gnu.org/software/autoconf

[3] https://www.gnu.org/software/automake

[4] https://www.gnu.org/software/libtool

[5] https://www.gnu.org/software/gnulib

[6] Since version 2.19.

[7] Since version 2.19.

[8] Since version 2.18

[9] Since version 2.22.

[10] Since version 2.22 the type can be specified

[11] Since version 2.20.

[12] Since version 2.15.

[13] Since version 2.16.

[14] This is true since version 2.19. Before this version, strings were not allowed to spawn more than one line.

[15] Since version 2.19.

[16] This holds since version 2.15: in previous versions the option specifications had to be given in a fixed order.

[17] Before version 2.22 neither `--help` was added and you had to handle the help option manually

[18] Since version 2.16.

[19] Since version 2.22.

[20] Since version 2.18.

[21] as it was up to version 2.22.2 of gengetopt.

[22] This is taken from the comments in `getopt.in.h` of gnulib.

[23] Since version 2.22 this field is of type `unsigned int` instead of `int` for uniformity with multiple options.

[24] The `<option>_orig` was introduced in the release 2.14.

[25] These strings and the `<option>_help` were introduced in the release 2.17.

[26] This function was introduced in the release 2.14.

[27] Introduced in version 2.22, thanks to Papp Gyozo.

[28] Since version 2.17.

[29] Since version 2.22.3.

[30] Since version 2.22.

[31] Since version 2.21.

[32] Introduced in version 2.22

[33] The `<cmd_parser_name>_params_init` was introduced in version 2.21, but it used to initialize all its fields to 0, which does not make much sense, since it's more helpful to have the fields initialized to their default values; in order not to silently break the semantics of previous code, the (void argument) creation function is now called `<cmd_parser_name>_params_create` and `<cmd_parser_name>_params_init` is now a procedure that initializes a passed pointer to the structure. This will make previous code not compilable, since the signature of `<cmd_parser_name>_params_init` has changed; hopefully, this will force the programmer to realize that something has changed. I'm sorry for the (hopefully little) problems this change might imply.

[34] The previous function `<cmd_parser_name>_configfile` — notice the absence of the `_` — is deprecated and should be no longer used, since it might be removed in the future releases.

[35] The previous function `<cmd_parser_name>2` — notice the `2` — is deprecated and should be no longer used, since it might be removed in the future releases.

[36] The previous function `<cmd_parser_name>_string2` — notice the `2` — is deprecated and should be no longer used, since it might be removed in the future releases.

[37] https://www.gnu.org/software/gnulib

[38] `optind` is the global variable in getopt implementation that is the index in ARGV of the next element to be scanned. This is used for communication to and from the caller and for communication between successive calls to `getopt_long`.