sh-c

#!/bin/sh
# sh-c (part of ossobv/vcutil) // wdoekes/2020 // Public Domain
#
# Helper to allow more complex shebangs to be executed.
#
# When executing a script, the shebang value is split into a program and
# a single argument. For example: /usr/bin/env (program) + python (argument).
# This script is a shortcut for "sh -c '<argument>'", so you can write a
# small shell script as the second argument.
#
# For example, you could do py3-or-py2.py:
#
#     #!/usr/bin/sh-c exec "$(which python3 python false|head -n1)" "$0" "$@"
#     import sys
#     print(sys.argv)
#     print(sys.version)
#
# Which would amount to calling this helper:
#
#     sh-c 'exec "$(which python3 python false|head -n1)" "$0" "$@"' \
#       py3-or-py2.py ARGS..
#
# Which would result in:
#
#     sh -c 'exec "$(which python3 python false|head -n1)" "$0" "$@"' \
#       py3-or-py2.py ARGS..
#
# Yielding one of these, depending on whether python3 existed:
#
#     ['py3-or-py2.py', 'ARGS..']
#     3.6.9 (default, Nov  7 2019, 10:44:02)
#     [GCC 8.3.0]
#
#     ['py3-or-py2.py', 'ARGS..']
#     2.7.17 (default, Nov  7 2019, 10:07:09)
#     [GCC 7.4.0]
#
# BUGS/CAVEATS:
#
# - You cannot use '/usr/bin/env sh-c', so this MUST be in /usr/bin/.
#
# - The fact that we need this helper. If /bin/sh accepted -cSCRIPT
#   as a single argument, we wouldn't even need this.
#
exec /bin/sh -c "$@"