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正則表達(dá)式(regular expression)描述了一種字符串匹配的模式（pattern），可以用來(lái)檢查一個(gè)串是否含有某種子串、將匹配的子串替換或者從某個(gè)串中取出符合某個(gè)條件的子串等，本篇文章為大家講解一下Linux正則表達(dá)式。
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元字符通常在Linux中分為兩類：Shell元字符，由Linux Shell進(jìn)行解析； 正則表達(dá)式元字符，由vi/grep/sed/awk等文本處理工具進(jìn)行解析； 正則表達(dá)式一般以文本行進(jìn)行處理，在進(jìn)行下面實(shí)例之前，先為grep命令設(shè)置–color參數(shù)：
class="">$ alias grep='grep --color=auto'
這樣每次過濾出來(lái)的字符串都會(huì)帶色彩了。
在開始之前還需要做一件事情，就是創(chuàng)建一個(gè)測(cè)試用的re-file文件，內(nèi)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 正則表達(dá)式元字符
教你3分鐘搞定Linux正則表達(dá)式教你3分鐘搞定Linux正則表達(dá)式
特殊的元字符
教你3分鐘搞定Linux正則表達(dá)式教你3分鐘搞定Linux正則表達(dá)式
擴(kuò)展的正則表達(dá)式
教你3分鐘搞定Linux正則表達(dá)式教你3分鐘搞定Linux正則表達(dá)式
實(shí)操
匹配以love開頭的所有行
class="">$ grep '^love' re-file
love, how much I adore you. Do you know
匹配love結(jié)尾的所有行
class="">$ grep 'love$' re-file
clover. Did you see them? I can only hope love.
匹配以l開頭，中間包含兩個(gè)字符，結(jié)尾是e的所有行
class="">$ 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個(gè)或多個(gè)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 # 對(duì)l不區(qū)分大小寫
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范圍內(nèi)的任何字符行，所有的小寫字符
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字符重復(fù)2到4次
class="">$ grep 'o\{2,4\}' re-filegroove.
重復(fù)o字符至少2次
class="">$ grep 'o\{2,\}' re-filegroove.
重復(fù)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. 重復(fù)前一個(gè)字符一個(gè)或一個(gè)以上
class="">$ egrep "go+d" linux.txt
Linux is a good
god assdxw bcvnbvbjk
gooodfs awrerdxxhkl
good
#####0個(gè)或者一個(gè)字符
ansheng@Ubuntu:/tmp$ egrep "go?d" linux.txt
god assdxw bcvnbvbjk
gdsystem awxxxx
或，查找多個(gè)字符串
class="">$ egrep "gd|good" linux.txt
Linux is a good
gdsystem awxxxx
good
分組過濾匹配
class="">$ egrep "g(la|oo)d" linux.txt
Linux is a good
glad
good
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