build argument lists containing whitespace

Question

In bash one can escape arguments that contain whitespace.

foo \"a string\"

This also works for arguments to a command or function:

Answer 1

Use arrays (one of the hidden features in Bash).

Answer 2

You can use the arrays just as you suggest, with a small detail changed. The line calling foo should read

 foo "${args[@]}"

Answer 3

Here is a shorter version which does not require the use of a numeric index:

(example: building arguments to a find command)

dir=$1
shift
for f in "$@" ; do
    args+=(-iname "*$f*")
done
find "$dir" "${args[@]}"

Answer 4

I had a problem with this too as well. I was writing a bash script to backup the important files on my windows computer (cygwin). I tried the array approach too, and still had some issues. Not sure exactly how I fixed it, but here's the parts of my code that are important in case it will help you.

WORK="d:\Work Documents\*"
#   prompt and 7zip each file
for x in $SVN $WEB1 $WEB2 "$WORK" $GRAPHICS $W_SQL
do
    echo "Add $x to archive? (y/n)"
    read DO
    if [ "$DO" == "y" ]; then
        echo "compressing $x"
        7zip a $W_OUTPUT "$x"
    fi
    echo ""
done

Answer 5

There are (at least) two ways to do this:

1. Use an array and expand it using "${array[@]}":

   bar() {
       local i=0 args=()
       for arg in "$@"
       do
           args[$i]="prefix $arg"
           ((++i))
       done
   
       foo "${args[@]}"
   }
   

   So, what have we learned? "${array[@]}" is to ${array[*]} what "$@" is to $*.

2. Or if you do not want to use arrays you need to use eval:

   bar() {
       local args=()
       for arg in "$@"
       do
           args="$args \"prefix $arg\""
       done
   
       eval foo $args
   }