shell ——grep

grep -q 用于if 逻辑判断很好用。
-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。如果有匹配的内容则立即返回状态值0。

小应用

# cat a.txt
nihao 
nihaooo
hello

#  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; fi
no

 

1. grep -q "abcdef" a.txt
2. if [ $? == 0 ]; then#查找成功
3.     echo xxoo
4. else
5.     echo ooxx
6. fi