The case of the supersized shebang

The case of the supersized shebang

It's much less common with the "modern" scripting languages (python/ruby), since they're usually treated as full-featured programming environments quite separate to any functionality they have as an interactive shell experience.

Guile is pretty close, with a "\" "meta switch" and defining #! ... !# as comment delimiters. You can do this:

#!/usr/local/bin/guile \
-e main -s
!#
(define (main args)
  (display "hello, world!")
  (newline))

Many other "scripting" languages use # as a comment character and can do some similar shell bootstrap hack too. Most of these are used to lookup the language interpreter in the path, knowing only that /bin/sh exists.

For some reason I never understood, the modern world has decided it is better to assume that /usr/bin/env exists instead (using env in this way still doesn't allow multiple args, unless you're using freebsd's env -S magic arg - also in coreutils 8.30 apparently).

Perl:

#!/bin/sh
#! -*-perl-*-
eval 'exec perl -x -wS $0 ${1+"$@"}'
    if 0;
# perl code continues here

Python:

#!/bin/sh
''':'
if type python2 >/dev/null 2>/dev/null; then
  exec python2 "$0" "$@"
else
  exec python "$0" "$@"
fi
'''
# Python code continues here