NGS(1)

NAME
ngs - Next Generation Shell.

SYNOPSIS
ngs script_name.ngs [arguments]

ngs [-e|-E|-p|-pi|-pj|-ppj|-pl|-pjl|-pt] expression [arguments]

ngs [-h|–help]

DESCRIPTION
ngs is a Next Generation Shell. It has two main parts: the language and the interactive shell.

OPTIONS
Given script_name, runs the script. The script runs top to bottom. If the script defines main function/multimethod, it is automatically invoked (after the top-to-bottom run), with command line arguments converted to appropriate types. If no main is defined (or main did not match the arguments) and the result of top-to-bottom execution is a Namespace (ns { ... }) and at least one command line argument was passed, the first command line argument is taken as function/multimethod name in the Namespace to run.

If script_name is ., ngsfile is used as the script_name.

Using expression in the options described below is equivalent to running a script that consists of { expression }.

-e evaluates the expression.

-E prevents loading of stdlib.ngs and evaluates the expression.

-p prints the resulting expression value in a human readable NGS format.

-pi prints inspect(...) (detailed information) of the resulting expression value.

-pj prints the resulting expression value as JSON.

-ppj prints the resulting expression value as pretty JSON. Requires jq to be installed.

-pl prints elements of the result, one per line (mnemonic “print lines”)

-pjl prints elements of the result, one per line as JSON (mnemonic “print JSON lines”)

-pt prints the resulting expression value as a table.

-h and –help shows help

MOTIVATION
NGS tries to fill the void between classical shells such as bash and general-purpose programming languages such as Ruby, Python, Perl, Go. The shells are domain-specific languages but the domain has changed so classical shells are not optimal for today’s tasks. General-purpose languages on the other hand are not domain-specific so they are not good as shells and too verbose for system tasks scripting, not a good fit.

EXAMPLES
For examples, see ngstut(1).

EXIT STATUS
The exit code is whatever the running code (script_name or expression) returns using the following conversions:

•   Int (integer) - used directly as exit code (modulo 256). For example, ngs -E 10 returns exit code 10.

•   Bool (boolean) - true results 0, false results 1.

•   T (a user-defined type) - The exit code can be customized by ExitCode(x:T) method.

•   Anything else, including user-defined types without ExitCode(x:T) method will result 0.

In case of an uncaught exception, the exit code is 240. In cases where additional errors were encountered during exiting, the exit codes will be greater than 240, ngslang(1) has specific information on that.

ENVIRONMENT

•   DEBUG - when non-empty string, switches on debug method output (default is off). It’s recommended to use debug("my debug info") in your scripts for turning debug output on and off easily, using the DEBUG environment variable.

•   NGS_BOOTSTRAP points to the bootstrap NGS file. On NGS startup this file is always run. Defaults to built-in stdlib with bootsrapper.

•   NGS_BOOTSTRAP_DEBUG - if defined, show bootstrap.ngs debugging information.

•   NGS_PATH (defaults to $HOME/.ngs:/opt/local/etc/ngs:/opt/local/lib/ngs:/etc/ngs:/usr/lib/ngs) - location of the autoload directory. Files are automatically loaded from this directory when an undefined global variable is used.

•   NGS_EXIT_BACKTRACE - print backtrace when exit() is called.

•   NGS_WARN_BACKTRACE - print backtrace when warn() is called. Prints only unique backtraces.

•   NGS_ERROR_BACKTRACE - print backtrace when error() is called. Prints only unique backtraces.

FILES

  stdlib.ngs
Packaged into ngs binary during build. Standard library. Defines many methods and autoloading behaviour.

SEE ALSO

ngstut(1) | NGS language tutorial
ngslang(1) | NGS language manual
ngswhy(1) | Motivation behind creation of NGS
ngsstyle(1) | Recommended style for NGS scripts

THANKS
Thanks to Zeev Glozman for Mac support, CMake contribution and other help.
Thanks to Ricardo Gomes for feedback, fixes to documentation, and other contributions.
Thanks to Guy Egozy, Avishai Ish-Shalom and other friends for ideas and feedback.
Thanks to Rui Chen for Homebrew related fixes and GitHub actions fixes.

AUTHORS
Ilya Sher.