grep -q用於if邏輯判斷

grep -q用於if邏輯判斷 突然發現grep -q 用於if 邏輯判斷很好用。 -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.   中文意思為，安靜模式，不列印任何標準輸出。如果有匹配的內容則立即返回狀態值0。 小應用 # cat a.txtnihao nihaooohello #  if  grep -q hello a.txt ; then echo yes;else echo no; fi yes# if grep -q word a.txt; then echo yes; else echo no; fino