shcmp

Compare outputs using different shells

Usage: shcmp -h|--help | [--NOERR] [--TIME] arg...
       shcmp --SHELL shell [arg...]

Run different shells with arg... and cluster by output + exit-code.
Succeeds only when all shells behave the same (one cluster).
Note: any unrecognized option, e.g. -c, is considered the begining of arg.

  --NOERR  Capture and cluster by stdout only, else (default) stdout+stderr.
  --TIME   Measure durations - expects $SHCMP_TIME_FILE or time.sh at $PATH .
           See https://github.com/avih/time.sh .
  --SHELL  Run shcmp-name `shell' [arg...] without processing or redirections.

Home: https://github.com/avih/shcmp

Example:

Not all shells support the non standard local command, and some need to quote assignments in local. This shows how different shells behave in this regard:

shcmp -c 'f() { local x=$(echo A B) && echo "|$x|"; }; f'

The above might produce the following output, depending on shells availability and versions:

= sh, dash_058, posh:
|A|
(exit:0)

= bash, bash_posix, busybox_ash, dash_0511, mksh, mksh_posix:
|A B|
(exit:0)

= ksh93:
ksh93: local: not found [No such file or directory]
(exit:127)

Note that the captured output also includes stderr (the error message for ksh93). Use --NOERR to prevent that and capture only stdout.

shcmp can also be used to compare the output of a script. E.g. use shcmp ./myscript foo bar to run ./myscript with two arguments in all shells and compare their outputs.

--TIME

Using this option will measure the execution time at each shell and display a sorted summary. For instance this command:

shcmp --TIME -c 'i=50000; while [ $i != 0 ]; do i=$((i-1)); done; echo OK'

may have an output similar to this:

-----
1283 ms, 1 ms/measure, Linux/dash
-----
 325 ms  25 %  bash
 205 ms  16 %  oksh
 186 ms  14 %  bb_ash
 182 ms  14 %  mksh
 156 ms  12 %  ksh93
 150 ms  12 %  pdksh
  79 ms   6 %  dash
-----
= dash, bash, bb_ash, mksh, pdksh, ksh93, oksh:
OK

In order for --TIME to work, you will need to place time.sh at your $PATH or specify it with $SHCMP_TIME_FILE. See https://github.com/avih/time.sh .

Alternatively, you can measure and summarize yourself by defining the functions shcmp_time_init, shcmp_time_switch_to <name> and shcmp_time_finish at ~/.shcmprc (see below). The functions are called from the same shell context.

~/.shcmprc

shcmp includes a built-in sample list of common shells and some posix variants (function wrappers with additional arguments).

If the file ~/.shcmprc exists, then it's sourced and replaces the list of built-in shells (and wrapper functions). It should set the variable shells to a space-separated list of shells to run. This list may also include function names - which this file should define too.

E.g. ~/.shcmprc:

myshell()       { /path/to/myshell "$@"; }
myshell_posix() { /path/to/myshell -o posix "$@"; }

shells="bash sh myshell myshell_posix"

You could also use ~/.shcmprc to support setting the list via an environment variable, e.g. replacing the last line at the file above with:

[ "${shells-}" ] || shells="bash sh myshell myshell_posix"

Will allow running this: shells="sh myshell_posix" shcmp ./myscript .

Additionally, if sourcing ~/.shcmprc results in a non-0 status (e.g. if its last command is false), then the built-in list is used instead.