grep command examples
Table of Contents
本文部分摘译自15 Practical Grep Command Examples In Linux / UNIX
本文使用下面的文件作为 grep 的对象。
$ cat demo_file
THIS LINE IS THE 1ST UPPER CASE LINE IN THIS FILE.
this line is the 1st lower case line in this file.
This Line Has All Its First Character Of The Word With Upper Case.
Two lines above this line is empty.
And this is the last line.
1 在文件中查找指定的字符串，可以一次在多个文件查找
$ cp demo_file demo_file2 $ echo grep "Character" demo* grep Character demo_file demo_file2 $ grep "Character" demo* demo_file:This Line Has All Its First Character Of The Word With Upper Case. demo_file2:This Line Has All Its First Character Of The Word With Upper Case.
如 echo 显示的，这里是 $SHELL 自身把 demo* 解析成两个文件，grep看到的还是两个文件
2 -i 忽略大小写
grep默认是大小写区分的，通过 -i 可以忽略大小写
$ grep the demo_file this line is the 1st lower case line in this file. And this is the last line. $ grep -i the demo_file THIS LINE IS THE 1ST UPPER CASE LINE IN THIS FILE. this line is the 1st lower case line in this file. This Line Has All Its First Character Of The Word With Upper Case. And this is the last line.
3 使用正则表达式
3.1 使用锚点
^：必须出现在行首$：必须出现在行尾
3.2 使用通配符
.：匹配任意字符[abc149]：匹配[]里的任意字符[a-c14-9]：同上[:digit:]：同[0-9][:alnum:]：同[0-9A-Za-z][:alpha:]：同[A-Za-z]
3.3 重复次数
?：匹配0次或1次*：匹配任意次+：匹配至少1次{n}：匹配n次{n,}：匹配至少n次{,m}：最多匹配m次{n,m}：匹配n次到m次之间
3.4 查找th开头，后跟2个字符的行
主意grep和egrep的差别8
$ grep 'th[a-z]\{2\}' demo_file this line is the 1st lower case line in this file. Two lines above this line is empty. And this is the last line. $ egrep 'th[a-z]{2}' demo_file this line is the 1st lower case line in this file. Two lines above this line is empty. And this is the last line.
4 -w 匹配完整的单词
$ grep is demo_file this line is the 1st lower case line in this file. This Line Has All Its First Character Of The Word With Upper Case. Two lines above this line is empty. And this is the last line. $ grep -w is demo_file this line is the 1st lower case line in this file. Two lines above this line is empty. And this is the last line.
5 -B 显示匹配行的前几行， -A 显示后几行， -C 显示前后几行
$ grep -B 2 empty demo_file
This Line Has All Its First Character Of The Word With Upper Case.
Two lines above this line is empty.
$ grep -A 1 empty demo_file
Two lines above this line is empty.
And this is the last line.
$ grep -C 3 empty demo_file
this line is the 1st lower case line in this file.
This Line Has All Its First Character Of The Word With Upper Case.
Two lines above this line is empty.
And this is the last line.
6 --color 高亮现实匹配到的字符串
$ grep --color=always empty demo_file Two lines above this line is empty.
7 其它很有用的选项
-r：递归查找-n：显示行号-c：只显示匹配了多少次-o：只显示匹配到的内容（默认是匹配到的行）-l：只显示匹配到的文件，用于单行内容特别长的情况-v：只显示不匹配的-q：关闭输出，通过$?判断是否匹配成功-a：把二进制文件当文本处理-F：不使用正则，使用文本匹配