在awk程序中让shell插入索引:

Have the shell interpolate the index in the awk program:

echo "1,2,3,4" | awk -F, -v OFS=, '{$'$index'="NEW"; print }'

注意最初的单引号 awk 程序是如何分成三个部分的，一个单引号开头的 '{$'，插入的索引值，然后是程序的单引号剩余部分.

Note how the originally single quoted awk program is split in three parts, a single quoted beginning '{$', the interpolated index value, followed by the single quoted remainder of the program.