3分钟搞定Linux系统正则表达式

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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：
class="">$ 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：

class="">$ cat re-fileI had a lovely time on our little picnic.Lovers were all around us. It is springtime. Ohlove, how much I adore you. Do you knowthe extent of my love? Oh, by the way, I thinkI lost my gloves somewhere out in that field ofclover. Did you see them?  I can only hope love.is forever. I live for you. It's hard to get back in thegroove. class="">$ cat linux.txtLinux is a good god assdxw bcvnbvbjkgreatttttt  wexcvxcoperaaaating  dhfghfvxgooodfs awrerdxxhklgdsystem awxxxxgladgood正则表达式元字符

                               
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特殊的元字符

                               
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扩展的正则表达式

                               
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实操
匹配以love开头的所有行
class="">$ grep '^love' re-filelove, how much I adore you. Do you know匹配love结尾的所有行
class="">$ grep 'love$' re-fileclover. Did you see them?  I can only hope love.匹配以l开头，中间包含两个字符，结尾是e的所有行
class="">$ grep 'l..e' re-fileI had a lovely time on our little picnic.love, how much I adore you. Do you knowthe extent of my love? Oh, by the way, I thinkI lost my gloves somewhere out in that field ofclover. 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
class="">$ grep ' *love' re-fileI had a lovely time on our little picnic.love, how much I adore you. Do you knowthe extent of my love? Oh, by the way, I thinkI lost my gloves somewhere out in that field ofclover. Did you see them?  I can only hope love.匹配love或Love
class="">$ 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. Ohlove, how much I adore you. Do you knowthe extent of my love? Oh, by the way, I thinkI lost my gloves somewhere out in that field ofclover. Did you see them?  I can only hope love.匹配A-Z的字母，其次是ove
class="">$ grep '[A-Z]ove' re-fileLovers 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
class="">$ grep '[^A-Z]' re-fileI had a lovely time on our little picnic.Lovers were all around us. It is springtime. Ohlove, how much I adore you. Do you knowthe extent of my love? Oh, by the way, I thinkI lost my gloves somewhere out in that field ofclover. Did you see them?  I can only hope love.is forever. I live for you. It's hard to get back in thegroove.匹配love
class="">$ grep 'love\.' re-fileclover. Did you see them?  I can only hope love.匹配空格
class="">$ grep '^$' re-file匹配任意字符
class="">$ grep '.*' re-fileI had a lovely time on our little picnic.Lovers were all around us. It is springtime. Ohlove, how much I adore you. Do you knowthe extent of my love? Oh, by the way, I thinkI lost my gloves somewhere out in that field ofclover. Did you see them?  I can only hope love.is forever. I live for you. It's hard to get back in thegroove.前面o字符重复2到4次
class="">$ grep 'o\{2,4\}' re-filegroove.重复o字符至少2次
class="">$ grep 'o\{2,\}' re-filegroove.重复0字符最多2次
class="">$ grep 'o\{,2\}' re-fileI had a lovely time on our little picnic.Lovers were all around us. It is springtime. Ohlove, how much I adore you. Do you knowthe extent of my love? Oh, by the way, I thinkI lost my gloves somewhere out in that field ofclover. Did you see them?  I can only hope love.is forever. I live for you. It's hard to get back in thegroove.重复前一个字符一个或一个以上
class="">$ egrep "go+d" linux.txtLinux is a goodgod assdxw bcvnbvbjkgooodfs awrerdxxhklgood#####0个或者一个字符ansheng@Ubuntu:/tmp$ egrep "go?d" linux.txtgod assdxw bcvnbvbjkgdsystem awxxxx

或，查找多个字符串

class="">$ egrep "gd|good" linux.txtLinux is a goodgdsystem awxxxxgood分组过滤匹配
class="">$ egrep "g(la|oo)d" linux.txtLinux is a goodgladgood

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编辑：朱培棋，审核员：逄增宝

296931987

很不错哦