Question

In bash one can escape arguments that contain whitespace.

foo 'a string' 

This also works for arguments to a command or function:

bar() {     foo '$@' }  bar 'a string' 

So far so good, but what if I want to manipulate the arguments before calling foo?

This does not work:

bar() {     for arg in '$@'     do         args='$args \'prefix $arg\''     done      # Everything looks good ...     echo $args      # ... but it isn't.     foo $args      # foo '$args' would just be silly }  bar a b c 

So how do you build argument lists when the arguments contain whitespace?

Answer 1

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 }