093-grep -q参数

grep -q 用于if逻辑判断，

-q 参数，本意是 Quiet; do not write anything to standard output.  Exit immediately with zero status if any match is found, even if an error was detected.   中文意思为，安静模式，不打印任何标准输出。若是有匹配的内容则当即返回状态值0。

         echo '1234' | grep -q 12

         echo $? 输出 0

         echo '1234' | grep 45

         echo $? 输出 1