Question

I want to execute a set of commands optionally in background and with bash. Something like this

#!/bin/bash
BGR=""
if [ foo ] ; then
   BGR=\&
fi
cmd1 $BGR
cmd2 $BGR
cmd3 $BGR
wait

But this doesn’t seem possible with bash. If foo is true, the commands evaluate to

+ cmd1 '&'
+ cmd2 '&'
+ cmd3 '&'

so the & is just another argument.

Is there any other way to achieve this? Besides code duplication, where I write if/then/else blocks with the different behavior.

Answer 1

You can move the if-else-clause to a function to avoid code duplication, e.g.:

function execute() {
    if [[ -n "$BGR" ]]; then
        "$@" &
    else
        "$@"
    fi
}

execute cmd1 arg1
execute cmd2 arg2