ANSHENG'S BLOG
Linux正则表达式范例
# linuxpublishDate · 2018-12-16 / lastEditedTime · 2022-04-06 04:49:00

正则表达式是一种字符模式,用于在查找过程中匹配制定的字符。

元字符通常在Linux中分为两类:

  • Shell元字符,由Linux Shell进行解析;

  • 正则表达式元字符,由vi/grep/sed/awk等文本处理工具进行解析;

正则表达式一般以文本行进行处理,在进行下面实例之前,先为grep命令设置--color参数:

$ alias grep='grep --color=auto'

这样每次过滤出来的字符串都会带色彩了。

在开始之前还需要做一件事情,就是创建一个测试用的re-file文件,内容如下:

$ cat re-file I had a lovely time on our little picnic. Lovers were all around us. It is springtime. Oh love, how much I adore you. Do you know the extent of my love? Oh, by the way, I think I lost my gloves somewhere out in that field of clover. Did you see them? I can only hope love. is forever. I live for you. It's hard to get back in the groove.

文件内容摘录自<<UNIX/SHELL范例精解第四版>>

$ cat linux.txt Linux is a good god assdxw bcvnbvbjk greatttttt wexcvxc operaaaating dhfghfvx gooodfs awrerdxxhkl gdsystem awxxxx glad good

正则表达式元字符

  • 特殊的元字符

  • 扩展的正则表达式

实操

  • 匹配以love开头的所有行
$ grep '^love' re-file love, how much I adore you. Do you know
  • 匹配love结尾的所有行
$ grep 'love$' re-file clover. Did you see them? I can only hope love.
  • 匹配以l开头,中间包含两个字符,结尾是e的所有行
$ grep 'l..e' re-file I had a lovely time on our little picnic. love, how much I adore you. Do you know the extent of my love? Oh, by the way, I think I lost my gloves somewhere out in that field of clover. Did you see them? I can only hope love. is forever. I live for you. It's hard to get back in the
  • 匹配0个或多个空行,后面是love的字符
$ grep ' *love' re-file I had a lovely time on our little picnic. love, how much I adore you. Do you know the extent of my love? Oh, by the way, I think I lost my gloves somewhere out in that field of clover. Did you see them? I can only hope love.
  • 匹配loveLove
$ grep '[Ll]ove' re-file # 对l不区分大小写 I had a lovely time on our little picnic. Lovers were all around us. It is springtime. Oh love, how much I adore you. Do you know the extent of my love? Oh, by the way, I think I lost my gloves somewhere out in that field of clover. Did you see them? I can only hope love.
  • 匹配A-Z的字母,其次是ove
$ grep '[A-Z]ove' re-file Lovers were all around us. It is springtime. Oh
  • 匹配不在A-Z范围内的任何字符行,所有的小写字符
$ grep '[^A-Z]' re-file I had a lovely time on our little picnic. Lovers were all around us. It is springtime. Oh love, how much I adore you. Do you know the extent of my love? Oh, by the way, I think I lost my gloves somewhere out in that field of clover. Did you see them? I can only hope love. is forever. I live for you. It's hard to get back in the groove.
  • 匹配love.
$ grep 'love\\.' re-file clover. Did you see them? I can only hope love.
  • 匹配空格
$ grep '^$' re-file
  • 匹配任意字符
$ grep '.*' re-file I had a lovely time on our little picnic. Lovers were all around us. It is springtime. Oh love, how much I adore you. Do you know the extent of my love? Oh, by the way, I think I lost my gloves somewhere out in that field of clover. Did you see them? I can only hope love. is forever. I live for you. It's hard to get back in the groove.
  • 前面o字符重复2到4次
$ grep 'o\\{2,4\\}' re-file groove.
  • 重复o字符至少2次
$ grep 'o\\{2,\\}' re-file groove.
  • 重复0字符最多2次
$ grep 'o\\{,2\\}' re-file I had a lovely time on our little picnic. Lovers were all around us. It is springtime. Oh love, how much I adore you. Do you know the extent of my love? Oh, by the way, I think I lost my gloves somewhere out in that field of clover. Did you see them? I can only hope love. is forever. I live for you. It's hard to get back in the groove.
  • 重复前一个字符一个或一个以
$ egrep "go+d" linux.txt Linux is a good god assdxw bcvnbvbjk gooodfs awrerdxxhkl good
  • 0个或者一个字符
ansheng@Ubuntu:/tmp$ egrep "go?d" linux.txt god assdxw bcvnbvbjk gdsystem awxxxx
  • 或,查找多个字符串
$ egrep "gd|good" linux.txt Linux is a good gdsystem awxxxx good
  • 分组过滤匹配
$ egrep "g(la|oo)d" linux.txt Linux is a good glad good