POSIX SH build loop variable with elements containing spaces

问题

Here's the code I need:

#!/bin/sh

x1="a1 a2"
x2="b1 b2"

list=SOMETHING

for x in "$list"
do
    echo $x
done

And the output I want:

a1 a2
b1 b2

The question is: what should SOMETHING be? I want $list to behave just as $@ does.

Notes: I can't use $IFS and I can't eval the entire loop.

回答1:

This is probably as close as you can get:

#!/bin/sh
x1="a1 a2"
x2="b1 b2"

set -- "$x1" "$x2"

for x in "$@"
do
    # echo $x
    echo "[${x}]"    # proves that the lines are being printed separately
done

Output:

[a1 a2]
[b1 b2]

In Bash you can use an array:

#!/bin/bash
x1="a1 a2"
x2="b1 b2"

list=("$x1" "$x2")

for x in "${list[@]}"
do
    # echo $x
    echo "[${x}]"    # proves that the lines are being printed separately
done

Same output.

回答2:

It is not possible in standard POSIX shell.

来源：https://stackoverflow.com/questions/2936922/posix-sh-build-loop-variable-with-elements-containing-spaces