ngs - Next Generation Shell.
ngs [-e|-E|-p|-pi|-pj|-pl|-pjl] expression
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.
Given script_name runs the script.
Using expression is equivalent to running a script that consists of
-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.
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")
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.
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 10returns exit code 10.
T(a user-defined type) - The exit code can be customized by
- 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.
DEBUG- when non-empty string, switches on
debugmethod 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
NGS_BOOTSTRAPpoints to the bootstrap NGS file. On NGS startup this file is always run. Defaults to first of:
NGS_BOOTSTRAP_DEBUG- if defined, show bootstrap.ngs debugging information.
/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.
NGS_EXIT_BACKTRACE- print backtrace when
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.
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.
NGS_DIR. Standard library. Defines many methods and autoloading behaviour.
|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 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.
- Ilya Sher