Re: converting array to string by quoting each element for eval

[Chris F.A. Johnson]

On Tue, 15 Nov 2011, Peng Yu wrote:

> Hi,
>
> I find that I have to make a program quotearg.sh to convert an array
> to a string by quoting each element. So that it be used for eval.
>
> I'm not sure if there is a way that I can do eval in bash without
> having to use quotearg.sh. If there is no such a way, should
> quotearg.sh be added in bash (if it is not available in bash yet), as
> it provides a fundamental functionality?
>
>
> ~/linux/bin/src/bash/quotearg/main$ cat ./main.sh
> #!/usr/bin/env bash
>
> ../quotearg.sh a b c
> ../quotearg.sh "'" ' ' '"'
> ../quotearg.sh 'a' 'a b'
>
> echo ================
>
> args=('a' 'a b')
> cmd="printf 'x%sx\n' ${args[@]}"
> eval "$cmd"

   Why not use the array instead of making it into a single string?

$cmd "${args[@]}"

   Why are you using eval or quotearg.sh? It sounds as if you are
   making the process more complicated than it need be.

   You should explain why you want it.

> echo ================#the following is what I want, the above is not.
>
> args=('a' 'a b')
> arg_string=`../quotearg.sh "${args[@]}"`
> cmd="printf 'x%sx\n' $arg_string"
> eval "$cmd"
>
> ~/linux/bin/src/bash/quotearg/main$  ./main.sh
> 'a' 'b' 'c'
> ''\''' ' ' '"'
> 'a' 'a b'
> ================
> xax
> xax
> xbx
> ================
> xax
> xa bx

--
   Chris F.A. Johnson, <http://cfajohnson.com/>
   Author:
   Pro Bash Programming: Scripting the GNU/Linux Shell (2009, Apress)
   Shell Scripting Recipes: A Problem-Solution Approach (2005, Apress)