学习老男孩Linux的笔记总结10【第67课】67-不断补充grep用法的笔记

过滤器，把想要的和不想要的分离开。
-v：排除

用法一：筛选出自己想要的字符串

用法二：筛选掉自己不想要的字符串剩下的字符串

[root@localhost oldboy]# cat test.txt
test
liyao
oldboy
[root@localhost oldboy]# grep "oldboy" test.txt      //用法一
oldboy
[root@localhost oldboy]# grep -v "oldboy" test.txt      //用法二
test
liyao
[root@localhost oldboy]# cat test.txt | grep -v "oldboy"
test
liyao

用法三：-i不区分大小写

[root@localhost oldboy]# cat a
111 aaaa
222 bbbb
333 ccc
444 DDD
555 ddd
[root@localhost oldboy]# grep -i "ddd" /home/oldboy/a
444 DDD
555 ddd

用法四：-E同时过滤多个字符.grep -E和egrep相同作用

[root@localhost oldboy]# cat a
111 aaaa
222 bbbb
333 ccc
444 DDD
555 ddd
[root@localhost oldboy]# grep -E "aaaa|bbbb" a    
111 aaaa
222 bbbb

[root@localhost oldboy]# egrep "aaaa|bbbb" a
111 aaaa
222 bbbb