Mini Shell

#!/usr/bin/bash
#
# ENVML, setup environment with module then run specified command
# Copyright (C) 2015-2022 CEA/DAM
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

##########################################################################


typeset progpath=$0
typeset prog=${progpath##*/}
typeset arg
typeset subarg
typeset kind_of_arg='mod'
typeset -a modarglist=()
typeset -a maymodarglist=()
typeset -a maycmdarglist=()
typeset -a cmdarglist=()


# print message on stderr then exit
echo_error() {
    echo "$prog: $1" >&2
    exit 1
}

arg_into_modaction() {
    # split module action from its argument
    local action="${1/=/ }"
    # split multiple arguments
    if [ "${action//;/ }" == "${action}" ]; then
        action="${action//&/ }"
    else
        # enable arg split over ';' to enable same behavior than envml.cmd
        action="${action//;/ }"
    fi

    case "$action" in
        purge*|restore*|unload*|switch*|load*) echo "$action"  ;;
        *) echo "load $action" ;;
    esac
}

# print usage message
echo_usage() {
    echo "Usage: $progpath [MODULE_ACTION]... [--] COMMAND [ARG]...
Run MODULE_ACTION(s) to setup environment then run COMMAND.

Syntax of supported MODULE_ACTIONs:
  purge                  unload all loaded modulefiles
  restore[=coll]         restore module list from collection named coll or
                         default collection if no collection name provided
  unload=mod1[&mod2...]  remove modulefile(s) mod1, (mod2...)
  switch=mod1&mod2       unload modulefile mod1 and load mod2
  [load=]mod1[&mod2...]  load modulefile(s) mod1, (mod2...)

Multiple MODULE_ACTION arguments can be specified as one argument by
separating them with a colon character (:).

To clearly separate command-line arguments from the module action arguments
a '--' argument can be used. Without this '--' separator, first argument is
considered module action and following arguments are part of command-line.

Examples:
  $progpath restore command arg1 arg2
  $progpath purge:mod1:mod2 command arg1 arg2
  $progpath restore load=mod1&mod2 -- command arg1 arg2"
}

# command help is asked
if [ $# -eq 0 ] || [ "$1" == '-h' ] || [ "$1" == '--help' ]; then
    echo_usage
    exit 0
fi

# parse arguments
for arg in "${@}"; do
    # reach separator, everything after is part of cmd
    if [ "$arg" == '--' ]; then
        kind_of_arg='cmd'
    else
        if [ "$kind_of_arg" == 'cmd' ]; then
            cmdarglist+=("$arg")
        else
            for subarg in ${arg//:/ }; do
                if [ "$kind_of_arg" == 'mod' ]; then
                    modarglist+=("$(arg_into_modaction "$subarg")")
                else
                    maymodarglist+=("$(arg_into_modaction "$subarg")")
                    maycmdarglist+=("$subarg")
                fi
            done

            # after first arg, we are not sure
            # following args are about module env
            if [ "$kind_of_arg" == 'mod' ]; then
                kind_of_arg='maymod'
            fi
        fi
    fi
done

# if a cmd separator has been found what we thought
# to be module-related is really module-related
if [ "$kind_of_arg" == 'cmd' ]; then
    modarglist+=("${maymodarglist[@]}")
# elsewhere what we thought to be module-related
# is in fact command-line related
else
    cmdarglist=("${maycmdarglist[@]}" "${cmdarglist[@]}")
fi


# check module function is defined
if ! typeset -F module >/dev/null; then
    echo_error "module command not found..."
fi

for arg in "${modarglist[@]}"; do
    module "$arg"
done

# now execute the real command with its interpreter
exec "${cmdarglist[@]}"