今天小编给大家分享一下Linux的正则表达式实例分析的相关知识点,内容详细,逻辑清晰,相信大部分人都还太了解这方面的知识,所以分享这篇文章给大家参考一下,希望大家阅读完这篇文章后有所收获,下面我们一起来了解一下吧。
正则表达式(regular expression)描述了一种字符串匹配的模式(pattern),可以用来检查一个串是否含有某种子串、将匹配的子串替换或者从某个串中取出符合某个条件的子串等。
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-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. class="">$ cat linux.txt Linux is a good god assdxw bcvnbvbjk greatttttt wexcvxc operaaaating dhfghfvx gooodfs awrerdxxhkl gdsystem awxxxx glad good
匹配以love开头的所有行
class="">$ grep '^love' re-file love, how much I adore you. Do you know
匹配love结尾的所有行
class="">$ grep 'love$' re-file clover. Did you see them? I can only hope love.
匹配以l开头,中间包含两个字符,结尾是e的所有行
class="">$ 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
class="">$ 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. 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
class="">$ 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
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.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
class="">$ egrep "gd|good" linux.txt Linux is a good gdsystem awxxxx good
分组过滤匹配
class="">$ egrep "g(la|oo)d" linux.txt Linux is a good glad good
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