ls和comm，在一起用需要注意些什么？

有一个脚本，处理一个一个服务器中无用的folders。其中用到了comm，comm是比较两个文件的异同，但是要求这两个文件的内容必须是被sort的。

这里ls把当前所有的目录都记录到/home/nova/nan/validation/tmp里，注意，这个tmp是需要与其他文件比较的，看似 ls > /home/nova/nan/validation/tmp 并没有在保存之前sort内容，但是ls命令本身就有sort的功能，罗列的文件是被sort之后的，所以这里不再需要sort命令！


例如如下，

#!/bin/env bash
# the delete the invalid folders in integration which do not exit in production.
# note: the script locates in /home/nova/scripts/graphite/ (created by nova account)
# but run by graphite account.
# full path is needed for this job.

echo '' > /home/xxxx/nan/validation/production_list

# list all valid folders to production_list
cd /opt/xxxx/storage/xxxxx/Opsview/GOP-xxxxxx/

find . -mindepth 3 -maxdepth 3 -type d | grep -ve \.\/int | cut -d\/ -f4 | \
sort | uniq > /home/nova/nan/validation/production_list

# delete invalid folders
lines=$(wc -l /home/xxxx/nan/validation/production_list | egrep -io [0-9]+)
if [ "$lines" -gt 2000 ];then
    for i in /opt/xxxx/storage/xxxxx/Opsview/GOP-xxxxxx/int*;
    do
        cd $i/RPM5
        ls > /home/xxxx/nan/validation/tmp
        for a in $(comm -23 /home/xxxx/nan/validation/tmp /home/nova/nan/validation/production_list)
        do
            #rm -rf $a
            ls -ld $a
        done
    done
else
    echo "$(date +%Y-%m-%d-%H-%M):error in /home/xxxx/nan/validation/production_list"
    >> /home/xxxx/nan/validation/dellog
fi