bash/shell的字符串trim实现

#!/bin/sh

trim()
{
    trimmed=$1
    trimmed=${trimmed%% }
    trimmed=${trimmed## }


    echo $trimmed
}

测试：
a=" x x "
b=" b b"
c="c c "
echo "=$a="
echo "=$b="
echo "=$c="

a=$(trim $a)
b=$(trim $b)
c=$(trim $c)
echo "=$a="
echo "=$b="
echo "=$c="

输出：
= x x =
= b b=
=c c =
=x=
=b=
=c=