NAME

ngs - Next Generation Shell.

SYNOPSIS

ngs script_name.ngs

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

DESCRIPTION

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

This project contains the language part which is under development. The interactive part will be dealt with later. This manual covers both implemented and unimplemented parts.

OPTIONS

Given script_name runs the script.

Using expression 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.

-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")

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.

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

In case of an uncaught exception, the exit code is 1.

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 easily be turning on/off.
• NGS_BOOTSTRAP points to the bootstrap NGS file. On NGS startup this file is always run. Defaults to first of:
  • $HOME/.bootstrap.ngs
  • /etc/ngs/bootstrap.ngs
  • /var/lib/ngs/bootstrap.ngs
  • /usr/share/ngs/bootstrap.ngs
• NGS_BOOTSTRAP_DEBUG - if defined, show bootstrap.ngs debugging information.
• NGS_DIR (defaults to /usr/share/ngs) - location of stdlib.ngs file and the autoload directory. Files are automatically loaded from this directory when an undefined global variable is used.

FILES

bootstrap.ngs

Typically located in NGS_DIR. Responsible for bootstrapping NGS.

• Loads stdlib.ngs if needed.
• Runs the script specified in the command line or exectes expression according to swithces.
• Prints expression value if needed.

stdlib.ngs

Located in NGS_DIR. Standard library. Defines many methods and autoloading behaviour.

SEE ALSO

THANKS

Thanks to Guy Egozy, Avishai Ish-Shalom and other friends for ideas and feedback.