# Lintian User's Manual

## Introduction

### About Lintian

Lintian is a Debian package checker. It can be used to check binary and source packages for compliance with the Debian policy and for other common packaging errors.

Lintian uses an archive directory, called laboratory, in which it stores information about the packages it examines. It can keep this information between multiple invocations in order to avoid repeating expensive data-collection operations. It's also possible to check the complete Debian archive for bugs — in a timely manner.

### The intention of Lintian

Packaging has become complicated—not because dpkg is complicated (indeed, dpkg-deb is very simple to use) but because of the high requirements of our policy. If a developer releases a new package, she has to consider hundreds of guidelines to make the package `policy compliant.'

All parts of our policy have been introduced by the same procedure: Some developer has a good idea how to make packages more `unique' with respect to a certain aspect—then the idea is discussed and a policy proposal is prepared. If we have a consensus about the policy change, it's introduced in our manuals.

Therefore, our policy is not designed to make life harder for the maintainers! The intention is to make Debian the best Linux distribution out there. With this in mind, lots of policy changes are discussed on the mailing lists each week.

But changing the policy is only a small part of the story: Just having some statement included in the manual does not make Debian any better. What's needed is for that policy to become `real life,' i.e., it's implemented in our packages. And this is where Lintian comes in: Lintian checks packages and reports possible policy violations. (Of course, not everything can be checked mechanically — but a lot of things can and this is what Lintian is for.)

Thus, Lintian has the following goals:

- To give us some impression of the `gap' between theory (written policy) and praxis (current state of implementation).

  From the results of the first two Lintian checks I implemented, I see that there is a big need to make this gap smaller. Introducing more policy aspects is worthless unless they are implemented. We first should fix packages to comply with current policy before searching for new ways to make policy more detailed. (Of course, there are also important policy changes that need to be introduced — but this is not what's meant here.)

- To make us re-think about certain aspects of our policy.

  For example, it could turn out that some ideas that once sounded great in theory are hard to implement in all our packages — in which case we should rework this aspect of policy.

- To show us where to concentrate our efforts in order to make Debian a higher quality distribution.

  Most release requirements will be implemented through policy. Lintian reports provide an easy way to compare all our packages against policy and keep track of the fixing process by watching bug reports. Note, that all this can be done automatically.

- To make us avoid making the same mistakes all over again.

  Being humans, it's natural for us to make errors. Since we all have the ability to learn from our mistakes, this is actually no big problem. Once an important bug is discovered, a Lintian check could be written to check for exactly this bug. This will prevent the bug from appearing in any future revisions of any of our packages.

### Design issues

There are three fields of application for Lintian:

- one person could use Lintian to check the whole Debian archive and reports bugs,

- each maintainer runs Lintian over her packages before uploading them,

- dinstall checks packages which are uploaded to master before they are installed in the archive.

The authors of Lintian decided to use a very modular design to achieve the following goals:

- flexibility: Lintian can be used to check single packages or the whole archive and to report and keep track of bug reports, etc.

- completeness: Lintian will eventually include checks for (nearly) everything that can be checked mechanically.

- uptodateness: Lintian will be updated whenever policy is changed.

- performance: Lintian should make it possible to check single packages within seconds or check the full archive within 5 days.

The design also has a number of constrains that limits the things Lintian can check for and what tools it can use:

- static analysis: The code in a package may be analyzed, but it should never be executed. However, Lintian can (and does) use external tools to analyze files in the package.

- deterministic replay-ability: Checks should not rely on the state of system caches or even the system time. These things makes it harder for others to reproduce (the absence of) tags.

- same source analysis: Lintian checks packages in small isolated groups based on the source package. Requiring the presence of all the dependencies to provide the full results make it harder to run lintian (not to mention, it makes "deterministic replay-ability" a lot harder as well).

### Disclaimer

Here is a list of important notes on how to use Lintian:

1. Lintian is not finished yet and will probably never be. Please don't use Lintian as a reference for Debian policy. Lintian might miss a lot of policy violations while it might also report some violations by mistake. If in doubt, please check out the policy manuals.

2. The Debian policy gives the maintainers a lot of freedom. In most cases, the guidelines included in the manuals allow exceptions. Thus, if Lintian reports a policy violation on a package and you think this is such an exception (or if you think Lintian has a bug) you can do two things: If your package is a bit non-standard and weird in this regard, you can install an override. If you think however that the check is too easily or outright wrongly triggered, please file a bug on the lintian package.

3. Please DO NOT use Lintian to file bug reports (neither single ones nor mass bug reports). This is done by the authors of Lintian already and duplication of efforts and bug reports should be avoided! If you think a certain bug is `critical' and should be reported/fixed immediately, please contact the maintainer of the corresponding package and/or the Lintian maintainers.

4. Any feedback about Lintian is welcome! Please send your comments to the lintian maintainers lintian-maint@debian.org.

## Getting started

### Installing Lintian

Before you can start to check your packages with Lintian, you'll have to install the `lintian` Debian package.

Alternatively you can checkout Lintian from the source repository and use that directly. By setting LINTIAN_ROOT (or using the --root option) lintian can be run from the source directory as if it had been installed on your system.

The only known caveat of using Lintian from the source directory is that Lintian requires a C.UTF-8 (or en_US.UTF-8) locale to correctly process some files. Lintian 2.5.5 supports using the C.UTF-8 locale from the `libc-bin` in Debian Wheezy.

If either your version of `libc-bin` or Lintian are too old, you can work around this issue by generating an en_US.UTF-8 locale. Alternatively, installing a copy of `lintian` should solve this, as older versions of Lintian generates a private locale at install time. Note, older versions of Lintian can only use the en_US.UTF-8 locale.

### Running lintian

After that, you can run Lintian on a changes file or any Debian binary, udeb or source packages like this:

    $ lintian libc5_5.4.38-1.deb
    W: libc5: old-fsf-address-in-copyright-file
    W: libc5: shlib-without-dependency-information usr/lib/libgnumalloc.so.5.4.38
    W: libc5: shlib-without-dependency-information lib/libc.so.5.4.38
    W: libc5: shlib-without-dependency-information lib/libm.so.5.0.9
    E: libc5: shlib-with-executable-bit lib/libc.so.5.4.38 0755
    E: libc5: shlib-with-executable-bit lib/libm.so.5.0.9 0755
    E: libc5: shlib-missing-in-control-file libgnumalloc usr/lib/libgnumalloc.so.5.4.38
    $

Please note that some checks are cross-package checks and can only be (accurately) performed if the binary packages and the source are processed together. If Lintian is passed a changes file, it will attempt to process all packages listed in the changes file.

Lintian supports a number of command line options, which are documented in the manpage of lintian(1). Some of the options may appear in the lintianrc file (without the leading dashes) in Lintian 2.5.1 (or newer).

### Lintian Tags

Lintian uses a special format for all its error and warning messages. With that it is very easy to write other programs which run Lintian and interpret the displayed messages.

The first character of each line indicates the type of message. Currently, the following types are supported:

Errors (E)

- The displayed message indicates a policy violation or a packaging error. For policy violations, Lintian will cite the appropriate policy section when it is invoked with the `-i` option.

Warnings (W)

- The displayed message might be a policy violation or packaging error. A warning is usually an indication that the test is known to sometimes produce false positive alarms, because either the corresponding rule in policy has many exceptions or the test uses some sort of heuristic to find errors.

Info (I)

- The displayed message is meant to inform the maintainer about a certain packaging aspect. Such messages do not usually indicate errors, but might still be of interest to the curious. They are not displayed unless the `-I` option is set.

Notes (N)

- The displayed message is a debugging message which informs you about the current state of Lintian.

Experimental (X)

- The displayed message is one of the types listed above, but has been flagged as `experimental' by the Lintian maintainers. This means that the code that generates this message is not as well tested as the rest of Lintian, and might still give surprising results. Feel free to ignore Experimental messages that do not seem to make sense, though of course bug reports are always welcome. They are not displayed unless the `-E` option is set.

Overridden (O)

- The displayed message indicates a previous Warning or Error message which has been overridden (see below). They are not displayed unless the `--show-overrides` option is set.

Pedantic (P)

- The displayed message indicates a message of Lintian at its most pickiest and include checks for particular Debian packaging styles, checks that are very frequently wrong, and checks that many people disagree with. They are not displayed unless the `--pedantic` option is set.

The type indicator is followed by the name of the package and for non-binary packages the type of the package. Then comes the problem that was discovered, also known as a tag (for example, `old-fsf-address-in-copyright-file`).

Depending on which tag has been reported, the line may contain additional arguments which tell you, for example, which files are involved.

If you do not understand what a certain tag is about, you can specify the `-i` option when calling Lintian to get a detailed description of the reported tags:

    $ lintian -i libc5_5.4.38-1.deb
    W: libc5: old-fsf-address-in-copyright-file
    N:
    N:   The /usr/share/doc/<pkg>/copyright file refers to the old postal
    N:   address of the Free Software Foundation (FSF). The new address is:
    N:
    N:     Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
    N:     MA 02110-1301, USA.
    N:
    N:   Severity: normal, Certainty: certain
    N:
    [...]
    $

In some cases, the messages contain some additional text with a leading hash character (`#`). This text should be ignored by any other programs which interpret Lintian's output because it doesn't follow a unique format between different messages and it's only meant as additional information for the maintainer.

### Overrides

In some cases, the checked package does not have a bug or does not violate policy, but Lintian still reports an error or warning. This can have the following reasons: Lintian has a bug itself, a specific Lintian check is not smart enough to know about a special case allowed by policy, or the policy does allow exceptions to some rule in general.

In the first case (where Lintian has a bug) you should send a bug report to the Debian bug tracking system and describe which package you checked, which messages have been displayed, and why you think Lintian has a bug. Best would be, if you would run Lintian again over your packages using the `-d` (or `--debug`) option, which will cause Lintian to output much more information (debugging info), and include these messages in your bug report. This will simplify the debugging process for the authors of Lintian.

In the other two cases (where the error is actually an exception to policy), you should probably add an override. If you're unsure though whether it's indeed a good case for an override, you should contact the Lintian maintainers too, including the Lintian error message and a short note, stating why you think this is an exception. This way, the Lintian maintainers can be sure the problem is not actually a bug in Lintian or an error in the author's reading of policy. Please do not override bugs in lintian, they should rather be fixed than overridden.

Once it has been decided that an override is needed, you can easily add one by supplying an overrides file. If the override is for a binary or udeb package, you have to place it at `/usr/share/lintian/overrides/`<package>`` inside the package. The tool `dh_lintian` from the Debian package `debhelper` may be useful for this purpose.

If the override is for a source package, you have to place it at `debian/source/lintian-overrides` or `debian/source.lintian-overrides` (the former path is preferred). With that, Lintian will know about this exception and not report the problem again when checking your package. (Actually, Lintian will report the problem again, but with type overridden, see above.)

Note that Lintian extracts the override file from the (u)deb and stores it in the laboratory. The files currently installed on the system are not used in current Lintian versions.

#### Format of override files

The format of the overrides file is simple, it consists of one override per line (and may contain empty lines and comments, starting with a `#`, on others): `[[`<package>`][ `<archlist>`][ `<type>`]: ]`<lintian-tag>`[ [*]`<lintian-info>`[*]]`. `<package>` is the package name; `<archlist>` is an architecture list (see Architecture specific overrides for more info); `<type>` is one of `binary`, `udeb` and `source`, and `<lintian-info>` is all additional information provided by Lintian except for the tag. What's inside brackets is optional and may be omitted if you want to match it all. An example file for a binary package would look like:

    /usr/share/lintian/overrides/foo, where foo is the name of your package

    # We use a non-standard dir permission to only allow the webserver to look
    # into this directory:
    foo binary: non-standard-dir-perm
    foo binary: FSSTND-dir-in-usr /usr/man/man1/foo.1.gz

An example file for a source package would look like:

    debian/source.lintian-overrides in your base source directory
    foo source: debian-files-list-in-source
    # Upstream distributes it like this, repacking would be overkill though, so
    # tell lintian to not complain:
    foo source: configure-generated-file-in-source config.cache

Many tags can occur more than once (e.g. if the same error is found in more than one file). You can override a tag either completely by specifying its name (first line in the examples) or only one occurrence of it by specifying the additional info, too (second line in the examples). If you add an asterisk (`*`) in the additional info, this will match arbitrary strings similar to the shell wildcard.

The first wildcard support appeared in Lintian 2.0.0, which only allowed the wildcards in the very beginning or end. Version 2.5.0~rc4 extended this to allow wildcards any where in the additional info.

#### Documenting overrides

To assist reviewers, Lintian will extract the comments from the overrides file and display the related comments next to the overridden tags.

Comments directly above an override will be shown next to all tags it overrides. If an override for the same tags appears on the very next line, it will inherit the comment from the override above it.

    # This comment will be shown above all tags overridden by the following
    # two overrides, (because they apply to the same tag and there is no
    # empty line between them)
    foo source: some-tag exact match
    foo source: some-tag wildcard * match
    # This override has its own comment, and it is not shared with the
    # override below (because there is an empty line in between them).
    foo source: some-tag another exact match

    foo source: some-tag override without a comment

Empty lines can be used to disassociate a comment from an override following it. This can also be used to make a general comment about the overrides that will not be displayed.

    # This is a general comment not connected to any override, since there
    # is one (or more) empty lines after it.

    foo source: another-tag without any comments

#### Architecture specific overrides

In rare cases, Lintian tags may be architecture specific. It is possible to mark overrides architecture specific by using the optional architecture list.

The architecture list has the same syntax as the architecture list in the "Build-Depends" field of a source package. This is described in detail in the Debian Policy Manual §7.1. Examples:

    # This is an example override that only applies to the i386
    # architecture.
    foo [i386] binary: some-tag optional-extra

    # An architecture wildcard would look like:
    foo [any-i386] binary: another-tag optional-extra

    # Negation also works
    foo [!amd64 !i386] binary: some-random-tag optional-extra

    # Negation even works for wildcards
    foo [!any-i386] binary: some-tag-not-for-i386 optional-extra

    # The package name and the package type is optional, so this
    # also works
    [linux-any]: tag-only-for-linux optional-extra.

Support for architecture specific overrides was added in Lintian 2.5.0. Wildcard support was added in 2.5.5. Basic sanity checking was also added in 2.5.5, where unknown architectures trigger a `malformed-override` tag. As does an architecture specific override for architecture independent packages.

### Vendor Profiles

Vendor profiles allows vendors and users to customize Lintian without having to modify the underlying code. If a profile is not explicitly given, Lintian will derive the best possible profile for the current vendor from dpkg-vendor.

#### Rules for profile names and location

Profile names should only consist of the lower case characters ([a-z]), underscore (_), dash (-) and forward slashes (/). Particularly note that dot (.) are specifically not allowed in a profile name.

The default profile for a vendor is called `$VENDOR/main`. If Lintian sees a profile name without a slash, it is taken as a short form of the default profile for a vendor with that name.

The filename for the profile is derived from the name by simply concatenating it with `.profile`, Lintian will then look for a file with that name in the following directories:

- `$XDG_DATA_HOME/lintian/profiles`

- `$HOME/.lintian/profiles`

- `/etc/lintian/profiles`

- `$LINTIAN_ROOT/profiles`

Note that an implication of the handling of default vendor profiles implies that profiles must be in subdirectories of the directories above for Lintian to recognise them.

The directories are checked in the listed order and the first file matching the profile will be used. This allows users to override a system profile by putting one with the same filename in `$XDG_DATA_HOME/lintian/profiles` or `$HOME/.lintian/profiles`.

#### Profile syntax and semantics

Profiles are written in the same syntax as Debian control files as described in the Debian Policy Manual §5.1. Profiles allow comments as described in the Policy Manual.

##### Main profile paragraph

The fields in the first paragraph are:

Profile (simple, mandatory)

- Name of the profile.

Extends (simple, optional)

- Name of the (parent) profile, which this profile extends. Lintian will recursively process the extended profile before continuing with processing this profile. In the absence of this field, the profile is not based on another profile.

Load-Checks (folded, optional)

- Comma-separated list of checks. Lintian will ensure all checks listed are loaded (allowing tags from them to be enabled or disabled via Enable-Tags or Disable-Tags).

  If a given check was already loaded before this field is processed, then it is silently ignored. Otherwise, the check is loaded and all of its tags are disabled (as if it had been listed in Disable-Tags-From-Check).

  This field is most likely only useful if the profile needs to enable a list of tags from a check in addition to any tags already enabled from that check (if any).

Enable-Tags-From-Check (folded, optional)

- Comma-separated list of checks. All tags from each check listed will be enabled in this profile. The check will be loaded if it wasn't already.

Disable-Tags-From-Check (folded, optional)

- Comma-separated list of checks. All tags from each check listed will be disabled in this profile. The check will be loaded if it wasn't already.

Enable-Tags (folded, optional)

- Comma-separated list of tags that should be enabled. It may only list tags from checks already loaded or listed in one of the following fields "Load-Checks", "Enable-Tags-From-Check" or "Disable-Tags-From-Check" in the current profile.

Disable-Tags (folded, optional)

- Comma-separated list of tags that should be disabled. It may only list tags from checks already loaded or listed in one of the following fields "Load-Checks", "Enable-Tags-From-Check" or "Disable-Tags-From-Check" in the current profile.

The profile is invalid and is rejected, if Enable-Tags and Disable-Tags lists the same tag twice - even if it is in the same field. This holds analogously for checks and the three fields Load-Checks, Enable-Tags-From-Check and Disable-Tags-From-Check.

It is allowed to list a tag in Enable-Tags or Disable-Tags even if the check that provides this tag is listed in the Disable-Tags-From-Check or Enable-Tags-From-Check field. In case of conflict, Enable-Tags / Disable-Tags shall overrule Disable-Tags-From-Check / Enable-Tags-From-Check within the profile.

Load-Checks, Enable-Tags-From-Check and Disable-Tags-From-Check can be used to load third-party or vendor specific checks.

It is not an error to load, enable or disable a check or tag that is already loaded, enabled or disabled respectively (e.g. by a parent profile).

A profile is invalid if it directly or indirectly extends itself or if it extends an invalid profile.

By default the tags from the check "lintian" will be loaded as they assist people in writing and maintaining their overrides file (e.g. by emitting `malformed-override`). However, they can be disabled by explicitly adding the check `lintian` in the Disable-Tags-From-Check field.

##### Tag alteration paragraphs

The fields in the secondary paragraphs are:

Tags (folded, mandatory)

- Comma separated list of tags affected by this paragraph.

Overridable (simple, optional)

- Either "Yes" or "No", which decides whether these tags can be overridden. Lintian will print an informal message if it sees an override for a tag marked as non-overridable (except if --quiet is passed).

Severity (simple, optional)

- The value must be a valid tag severity other than "classification". The severity of the affected tags is set to this value. This cannot be used on any tag that is defined as a "classification" tag.

  Note that experimental is not a severity.

The paragraph must contain at least one other field than the Tag field.

##### An example vendor profile

Below is a small example vendor profile for a fictive vendor called "my-vendor".

    # The default profile for "my-vendor"
    Profile: my-vendor/main
    # It has all the checks and settings from the "debian" profile
    Extends: debian/main
    # Add checks specific to "my-vendor"
    Enable-Tags-From-Check:
      my-vendor/some-check,
      my-vendor/another-check,
    # Disable a tag
    Disable-Tags: dir-or-file-in-opt

    # Bump severity of no-md5sums-control-file
    # and file-missing-in-md5sums and make them
    # non-overridable
    Tags: no-md5sums-control-file,
          file-missing-in-md5sums,
    Severity: serious
    Overridable: no

### Vendor specific data files

Lintian uses a number of data files for various checks, ranging from common spelling mistakes to lists of architectures. While some of these data files are generally applicable for all vendors (or Debian derivatives), others are not.

Starting with version 2.5.7, Lintian supports vendor specific data files. This allows vendors to deploy their own data files tailored for their kind of system. Lintian supports both extending an existing data file and completely overriding it.

#### Load paths and order

Lintian will search the following directories in order for vendor specific data files:

- `$XDG_DATA_HOME/lintian/vendors/`PROFILENAME`/data`

- `$HOME/.lintian/vendors/`PROFILENAME`/data`

- `/etc/lintian/vendors/`PROFILENAME`/data`

- `$LINTIAN_ROOT/vendors/`PROFILENAME`/data`

If none of the directories exists or none of them provide the data file in question, Lintian will (recursively) retry with the parent of the vendor (if any). If the vendor and none of its parents provide the data file, Lintian will terminate with an error.

#### Basic syntax of data files

Generally, data files are read line by line. Leading whitespace of every line is removed and (now) empty lines are ignored. Lines starting with a `#` are comments and are also ignored by the parser. Lines are processed in the order they are read.

If the first character of the line is a `@`, the first word is parsed as a special processing instruction. The rest of the line is a parameter to that processing instruction. Please refer to section-2.6.2.1-title.

All other lines are read as actual data. If the data file is a table (or map), the lines will parsed as key-value pairs. If the data file is a list (or set), the full line will be considered a single value of the list.

It is permissible to define the same key twice with a different value. In this case, the value associated with the key is generally redefined. There are very rare exceptions to this rule, where the data file is a table of tables (of values). In this case, a recurring key is used to generate the inner table.

##### List of processing instructions

The following processing instructions are recognised:

@delete `ENTRY`

- Removes a single entry denoted by `ENTRY` that has already been parsed.

  It is permissible to list a non-existent entry, in which case the instruction has no effect. This instruction does not prevent the entry from being (re-)defined later, it only affects the current definition of the entry.

  For key-pair based data files, `ENTRY` must match the key. For single value data files, `ENTRY` must match the line to remove.

@include-parent

- Processes parent data file of the current data file.

  The informal semantics of this instruction is that it reads the "next" data file in the vendor "chain". The parsing of the parent is comparable to a C-style include or sourcing a shell script.

  More formally, let `CP` be the name of the vendor profile that defines the data file containing the instruction. Let the parent of `CP` be referred to as `PCP`.

  Lintian will search for the data file provided by `PCP` using the rules as specified in section-2.6.1-title. If no data file is found, Lintian will terminate the parsing with an error. Thus, this instruction can only be used by profiles that extends other profiles.

## Advanced usage

### How Lintian works

Lintian is divided into the following layers:

frontend

- the command line interface (currently, this layer consists of two scripts, namely `lintian` and `lintian-info`)

checks

- a set of modules that check different aspects of packages.

data collectors

- a set of scripts that prepares specific information about a package needed by the check modules

When you check a package with Lintian, the following steps are performed (not exactly in this order—but the details aren't important now):

1. An entry is created for the package in the laboratory (or just lab).

2. Some data is collected about the package. (That is done by the so-called data collector scripts.) For example, the `file` program is run on each file in the package and the output is stored in the lab.

3. The checks are run over the package and report any discovered policy violations or other errors. These scripts don't access the package contents directly, but use the collected data as input.

4. Depending on the lab mode Lintian uses (see below), the whole lab directory is removed again. If the lab is not removed, parts of the data collected may be auto cleaned to reduce disk space.

This separation of the check from the data collector scripts makes it possible to run Lintian several times over a package without having to recollect all the data each time. In addition, the checker scripts do not have to worry about packaging details since this is abstracted away by the collector scripts.

### The laboratory

Lintian's laboratory directory can be defined via the `LINTIAN_LAB` variable (either in the configuration file or as environment variable). If this variable is not defined, Lintian creates a temporary lab in `/tmp` which is removed again after Lintian has completed its checks. This mode is called temporary lab mode.

In the static lab mode (if the laboratory directory is defined by the user), the laboratory has to be set up first before it can be used by Lintian. This can be done with the `-S` (or `--setup-lab`) command line option.

### Writing your own Lintian checks

This section describes how to write and deploy your own Lintian checks. Lintian will load checks from the following directories (in order):

- `$LINTIAN_ROOT/checks`

Existing checks can be shadowed by placing a check with the same name in a directory appearing earlier in the list. This also holds for the checks provided by Lintian itself.

Checks in Lintian consist of a description file (.desc) and a Perl module implementing the actual check (.pm). The names of these checks must consist entirely of the lower case characters ([a-z]), digits ([0-9]), underscore (_), dash (-), period (.) and forward slashes (/).

The check name must be a valid Perl unique module name after the following transformations. All periods and dashes are replaced with underscores. All forward slashes are replaced with two colons (::).

Check names without a forward slash (e.g. "fields") and names starting with either "lintian/" or "coll/" are reserved for the Lintian core. Vendors are recommended to use their vendor name before the first slash (e.g. "ubuntu/fields").

#### Check description file

The check description file is written in the same syntax as Debian control files as described in the Debian Policy Manual §5.1. Check description files allow comments as described in the Policy Manual.

The check description file has two paragraph types. The first is the check description itself and must be the first paragraph. The rest of the descriptions describe tags, one tag per paragraph.

##### Check description paragraph

The fields in the check description paragraph are:

Check-Script (simple, mandatory)

- Name of the check. This is used to determine the package name of the Perl module implementing the check.

Type (simple, mandatory)

- Comma separated list of package types for which this check should be run. Allowed values in the list are "binary" (.deb files), "changes" (.changes files), "source" (.dsc files) and "udeb" (.udeb files).

Needs-Info (simple, optional)

- Comma separated list of collections required for the check to be run. Common values here include "unpacked", "index" and "file-info".

Info (multiline, optional)

- A short description of what the check is for.

Author (simple, optional)

- Name and email of the person, who created (or implemented etc.) the check.

Abbrev (simple, optional)

- Alternative or abbreviated name of the check. These can be used with certain command line options as an alternative name for the check.

##### Tag description paragraph

The fields in the tag description paragraph are:

Tag (simple, mandatory)

- Name of the tag. It must consist entirely of the lower or/and upper case characters ([a-zA-Z]), digits ([0-9]), underscore (_), dash (-) and period (.). The tag name should be at most 68 characters long.

Severity (simple, mandatory)

- Determines the default value for how "severe" the tag is. The value must be one of "serious", "important", "normal", "minor", "wishlist" and "pedantic". The effective severity and the value of the Certainty field of a tag determine the "one-letter" code (of non-experimental tags).

Certainty (simple, mandatory)

- How accurate the tag is (believed to be). The value must be one of "certain", "possible", "wild-guess". The effective severity and the value of the Certainty field of a tag determine the "one-letter" code (of non-experimental tags).

Info (multiline, mandatory)

- The description of the tag, which can be seen by using lintian-info (etc.). The HTML tags "<tt>" and "<i>" may be used in the description.

  The symbols &, < and > must be escaped as &amp;, &lt; and &gt; (respectively).

  Indented lines are considered "pre-formatted" and will not be line wrapped. These lines are still subject to the allowed HTML tags and above mentioned escape sequences.

Ref (simple, optional)

- A comma separated list of references. It can be used to refer to extra documentation. It is primarily used for manual references, HTTP links or Debian bug references.

  If a reference contains a space, it is taken as a manual reference (e.g. "policy 4.14"). These references are recorded in the "output/manual-references" data file.

  Other references include manpages ("lintian(1)"), ftp or http(s) links ("https://lintian.debian.org"), file references ("/usr/share/doc/lintian/changelog.gz") or Debian bug numbers prefixed with a hash ("#651816").

  Unknown references are (silently) ignored.

Experimental (simple, optional)

- Whether or not the tag is considered "experimental". Recognised values are "no" (default) and "yes". Experimental tags always use "X" as their "one-letter" code.

#### Check Perl module file

This section describes the requirements for the Perl module implementing a given check.

The Perl package name of the check must be identical to the check name (as defined by the "Check-Script" field in the description file) with the following transformations:

- All periods and dashes are replaced with underscores.

- All forward slashes are replaced by two colons (::).

- The resulting value is prefixed with "Lintian::".

As an example, the check name `contrib/hallo-world` will result in the Perl package name `Lintian::contrib::hallo_world`.

##### API of the "run" sub

The Perl module must implement the sub called `run` in that Perl package. This sub will be run once for each package to be checked with 5 arguments. These are (in order):

- The package name.

- The package type being checked in this run. This string is one of "binary" (.deb), "changes" (.changes), "source" (.dsc) or "udeb" (.udeb).

- An instance of API Lintian::Collect. Its exact type depends on the type being processed and is one of Lintian::Collect::Binary (.deb or .udeb), Lintian::Collect::Changes (.changes) or Lintian::Collect::Source (.dsc).

- An instance of Lintian::Processable that represents the package being processed.

- An instance of Lintian::ProcessableGroup that represents the other processables in the given group. An instance of the Lintian::Collect::Group is available via its "info" method.

Further arguments may be added in the future after the above mentioned ones. Implementations should therefore ignore extra arguments beyond the ones they know of.

If the run sub returns "normally", the check was run successfully. Implementations should ensure the return value is undefined.

If the run sub invokes a trappable error (e.g. "die"), no further checks are done on the package and Lintian will (eventually) exit with 2 to its caller. The check may still be run on other packages.

The run sub may emit tags by invoking the sub "tag" from Lintian::Tags (it can be imported). The first argument is the name of the tag to emit. Any extra arguments will be used as the "tag extra" (or diagnostics). Example:

    use Lintian::Tags qw(tag);
    sub run {
        tag 'my-tag', 'hallo world';
        return;
    }

would emit the tag "my-tag" with the extra note "hallo world" like this:

    I: package: my-tag hallo world