Linux正则与grep命令

待我称王封你为后i 2022-01-16 03:48 255阅读 0赞

[2019独角兽企业重金招聘Python工程师标准>>> ][2019_Python_] ![hot3.png][]

### 什么是正则 ###

*  **正则就是一串有规律的字符串**
 *  掌握好正则对于编写shell脚本有很大帮助
 *  各种编程语言中都有正则，原理是一样的

### grep命令 ###

*  grep \[-cinvABC\] 'word' filename \#命令格式
 *  \-c 行数
 *  \-i 不区分大小写
 *  \-n 显示行号
 *  \-v 取反
 *  \-r 遍历所有子目录
 *  \-A 后面跟数字，过滤出符合要求的行以及下面n行
 *  \-B 后面跟数字，过滤出符合要求的行以及上面n行
 *  \-C 后面跟数字，同时过滤出符合要求的行以及上下各n行

[root@centos01 test_grep_dir]# grep 'nologin' passwd
    bin:x:1:1:bin:/bin:/sbin/nologin
    daemon:x:2:2:daemon:/sbin:/sbin/nologin
    adm:x:3:4:adm:/var/adm:/sbin/nologin
    lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
    mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
    operator:x:11:0:operator:/root:/sbin/nologin
    games:x:12:100:games:/usr/games:/sbin/nologin
    ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
    nobody:x:99:99:Nobody:/:/sbin/nologin
    dbus:x:81:81:System message bus:/:/sbin/nologin
    polkitd:x:999:998:User for polkitd:/:/sbin/nologin
    avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
    avahi-autoipd:x:170:170:Avahi IPv4LL Stack:/var/lib/avahi-autoipd:/sbin/nologin
    postfix:x:89:89::/var/spool/postfix:/sbin/nologin
    sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
    
    [root@centos01 test_grep_dir]# grep -c 'nologin' passwd
    15
    
    [root@centos01 test_grep_dir]# grep -n 'nologin' passwd
    2:bin:x:1:1:bin:/bin:/sbin/nologin
    3:daemon:x:2:2:daemon:/sbin:/sbin/nologin
    4:adm:x:3:4:adm:/var/adm:/sbin/nologin
    5:lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
    9:mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
    10:operator:x:11:0:operator:/root:/sbin/nologin
    11:games:x:12:100:games:/usr/games:/sbin/nologin
    12:ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
    13:nobody:x:99:99:Nobody:/:/sbin/nologin
    14:dbus:x:81:81:System message bus:/:/sbin/nologin
    15:polkitd:x:999:998:User for polkitd:/:/sbin/nologin
    16:avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
    17:avahi-autoipd:x:170:170:Avahi IPv4LL Stack:/var/lib/avahi-autoipd:/sbin/nologin
    18:postfix:x:89:89::/var/spool/postfix:/sbin/nologin
    19:sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
    
    [root@centos01 test_grep_dir]# grep -i 'Nologin' passwd
    bin:x:1:1:bin:/bin:/sbin/nologin
    daemon:x:2:2:daemon:/sbin:/sbin/nologin
    adm:x:3:4:adm:/var/adm:/sbin/nologin
    lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
    mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
    operator:x:11:0:operator:/root:/sbin/nologin
    games:x:12:100:games:/usr/games:/sbin/nologin
    ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
    nobody:x:99:99:Nobody:/:/sbin/nologin
    dbus:x:81:81:System message bus:/:/sbin/nologin
    polkitd:x:999:998:User for polkitd:/:/sbin/nologin
    avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
    avahi-autoipd:x:170:170:Avahi IPv4LL Stack:/var/lib/avahi-autoipd:/sbin/nologin
    postfix:x:89:89::/var/spool/postfix:/sbin/nologin
    sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
    
    [root@centos01 test_grep_dir]# grep -nvi 'Nologin' passwd
    1:root:x:0:0:root:/root:/bin/bash
    6:sync:x:5:0:sync:/sbin:/bin/sync
    7:shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
    8:halt:x:7:0:halt:/sbin:/sbin/halt
    20:snowball:x:1000:1000::/home/snowball:/bin/bash
    21:test01:x:1001:1001::/home/test01:/bin/bash
    22:test02:x:1002:1002::/home/test02:/bin/bash
    23:test03:x:1003:1004::/home/test03:/bin/bash
    24:test06:x:1004:1005::/home/test06:/bin/bash
    25:test07:x:1005:1006::/home/test07:/bin/bash
    26:test08:x:1006:1007::/home/test08:/bin/bash
    
    [root@centos01 test_grep_dir]# grep -r 'root' .
    ./passwd:root:x:0:0:root:/root:/bin/bash
    ./passwd:operator:x:11:0:operator:/root:/sbin/nologin
    ./sub/sudoers:## the root user, without needing the root password.
    ./sub/sudoers:## Allow root to run any commands anywhere
    ./sub/sudoers:root      ALL=(ALL)       ALL
    ./sub/sudoers:## cdrom as root
    
    [root@centos01 test_grep_dir]# grep -nA2 'root' passwd
    1:root:x:0:0:root:/root:/bin/bash
    2-bin:x:1:1:bin:/bin:/sbin/nologin
    3-daemon:x:2:2:daemon:/sbin:/sbin/nologin
    --
    10:operator:x:11:0:operator:/root:/sbin/nologin
    11-games:x:12:100:games:/usr/games:/sbin/nologin
    12-ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
    
    [root@centos01 test_grep_dir]# grep -nB2 'root' passwd
    1:root:x:0:0:root:/root:/bin/bash
    --
    8-halt:x:7:0:halt:/sbin:/sbin/halt
    9-mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
    10:operator:x:11:0:operator:/root:/sbin/nologin
    
    [root@centos01 test_grep_dir]# grep -nC2 'root' passwd
    1:root:x:0:0:root:/root:/bin/bash
    2-bin:x:1:1:bin:/bin:/sbin/nologin
    3-daemon:x:2:2:daemon:/sbin:/sbin/nologin
    --
    8-halt:x:7:0:halt:/sbin:/sbin/halt
    9-mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
    10:operator:x:11:0:operator:/root:/sbin/nologin
    11-games:x:12:100:games:/usr/games:/sbin/nologin
    12-ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
    
    [root@centos01 test_grep_dir]# grep -n '[7-9]' passwd # 内容含有7或8或9的行
    5:lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
    8:halt:x:7:0:halt:/sbin:/sbin/halt
    9:mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
    13:nobody:x:99:99:Nobody:/:/sbin/nologin
    14:dbus:x:81:81:System message bus:/:/sbin/nologin
    15:polkitd:x:999:998:User for polkitd:/:/sbin/nologin
    16:avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
    17:avahi-autoipd:x:170:170:Avahi IPv4LL Stack:/var/lib/avahi-autoipd:/sbin/nologin
    18:postfix:x:89:89::/var/spool/postfix:/sbin/nologin
    19:sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
    25:test07:x:1005:1006::/home/test07:/bin/bash
    26:test08:x:1006:1007::/home/test08:/bin/bash
    
    [root@centos01 test_grep_dir]# grep -nv '[7-9]' passwd # 内容不含有7或8或9的行
    1:root:x:0:0:root:/root:/bin/bash
    2:bin:x:1:1:bin:/bin:/sbin/nologin
    3:daemon:x:2:2:daemon:/sbin:/sbin/nologin
    4:adm:x:3:4:adm:/var/adm:/sbin/nologin
    6:sync:x:5:0:sync:/sbin:/bin/sync
    7:shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
    10:operator:x:11:0:operator:/root:/sbin/nologin
    11:games:x:12:100:games:/usr/games:/sbin/nologin
    12:ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
    20:snowball:x:1000:1000::/home/snowball:/bin/bash
    21:test01:x:1001:1001::/home/test01:/bin/bash
    22:test02:x:1002:1002::/home/test02:/bin/bash
    23:test03:x:1003:1004::/home/test03:/bin/bash
    24:test06:x:1004:1005::/home/test06:/bin/bash
    
    [root@centos01 test_grep_dir]# grep '^a' passwd # 以a开头的行
    adm:x:3:4:adm:/var/adm:/sbin/nologin
    avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
    avahi-autoipd:x:170:170:Avahi IPv4LL Stack:/var/lib/avahi-autoipd:/sbin/nologin
    
    [root@centos01 test_grep_dir]# grep 'r.o' passwd # .表示任意一个字符
    root:x:0:0:root:/root:/bin/bash
    operator:x:11:0:operator:/root:/sbin/nologin
    
    [root@centos01 test_grep_dir]# grep 'x:*11' passwd # *表示前面的字符零次或多次匹配
    operator:x:11:0:operator:/root:/sbin/nologin
    
    [root@centos01 test_grep_dir]# grep 'operator.*login' passwd # .* 任意个任意字符
    operator:x:11:0:operator:/root:/sbin/nologin
    
    [root@centos01 test_grep_dir]# grep 'o\{2\}' passwd # {n1, n2}表示前面字符的重复n1到n2次
    root:x:0:0:root:/root:/bin/bash
    tooost
    ooooost
    lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
    mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
    operator:x:11:0:operator:/root:/sbin/nologin
    postfix:x:89:89::/var/spool/postfix:/sbin/nologin
    [root@centos01 test_grep_dir]# grep 'o\{3,4\}' passwd # 重复3或4次o
    tooost
    ooooost
    
    # egrep 不需要针对特殊字符进行转义, 等价于grep -E
    [root@centos01 test_grep_dir]# egrep 'o{2}' passwd 
    root:x:0:0:root:/root:/bin/bash
    tooost
    ooooost
    lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
    mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
    operator:x:11:0:operator:/root:/sbin/nologin
    postfix:x:89:89::/var/spool/postfix:/sbin/nologin
    
    [root@centos01 test_grep_dir]# egrep '(oo){2}' passwd  # (oo) 把oo当做整体
    ooooost
    
    # + 表示1次或多次前面的字符，与*的差异是*有0次
    [root@centos01 test_grep_dir]# grep 'o\+o' passwd 
    root:x:0:0:root:/root:/bin/bash
    tooost
    ooooost
    lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
    mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
    operator:x:11:0:operator:/root:/sbin/nologin
    postfix:x:89:89::/var/spool/postfix:/sbin/nologin
    
    # ?表示0次或1次前面的字符
    [root@centos01 test_grep_dir]# grep 'ro\?ot' passwd
    root:x:0:0:root:/root:/bin/bash
    operator:x:11:0:operator:/root:/sbin/nologin
    # |表示匹配多个字符串，只要有其中任意一个字符串满足条件即可
    [root@centos01 test_grep_dir]# grep 'root\|operator' passwd
    root:x:0:0:root:/root:/bin/bash
    operator:x:11:0:operator:/root:/sbin/nologin

转载于:https://my.oschina.net/u/996931/blog/2247670

[2019_Python_]: https://my.oschina.net/u/2663968/blog/3061697
[hot3.png]: /images/20220114/dfe0381b76da4e3abec3933087eebde2.png