093-grep -q參數

grep -q 用於if邏輯判斷，

-q 參數，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.   中文意思爲，安靜模式，不打印任何標準輸出。若是有匹配的內容則當即返回狀態值0。

         echo '1234' | grep -q 12

         echo $? 輸出 0

         echo '1234' | grep 45

         echo $? 輸出 1