Pass shell-escaped string of arguments to a subcommand in Bourne shell

Question

Say I have a command I want to run (cmd) and a variable containing the arguments I want to pass to the function (something like --foo 'bar baz' qux). Like so:

#!/bin/sh
command=cmd
args="--foo 'bar baz' qux"

The arguments contain quotes, like the ones shown above, that group together an argument containing a space. I'd then like to run the command:

$command $args

This, of course, results in running the command with four arguments: --foo, 'bar, baz', and qux. The alternative I'm used to (i.e., when using "$@") presents a different problem:

$command "$args"

This executes the command with one argument: --foo 'bar baz' qux.

How can I run the command with three arguments (--foo, bar baz, and qux) as intended?

Answer 1

Use an array to specify your argument list exactly, without string-splitting (which is what's doing the wrong thing here) getting in your way:

args=( --foo "bar baz" qux )
command "${args[@]}"

If you need to build your argument list dynamically, you can append to arrays with +=:

args=( )
while ...; do
   args+=( "$another_argument" )
done
call_your_subprocess "${args[@]}"

Note that the use of quotation marks, and [@] instead of [*], is essential.

Answer 2

If you can throw away the current positional variables ($1...) you can use the following:

set -- '--foo' 'bar baz' 'qux'
echo "$#" # Prints "3" (without quotes)
echo "$2" # Prints "bar baz" (without quotes)
command "$@"

Just tested it in a #!/usr/bin/env sh script, so it works at least in Dash, and should work in any Bourne Shell variant. No eval, Python or Bash necessary.