【CentOS 7基础36】，正则之grep命令#

- 日理万妓 2022-10-02 00:42 204阅读 0赞

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

> shallow丿ove

--------------------

# grep #

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

[root@localhost ~]# mkdir grep
    [root@localhost ~]# cd grep
    [root@localhost grep]# cp /etc/passwd .
    [root@localhost grep]# ls
    	passwd
    [root@localhost grep]# pwd
    	/root/grep
    [root@localhost grep]# 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@localhost grep]# which grep
    	alias grep='grep --color=auto'
    		/usr/bin/grep
    [root@localhost grep]# /usr/bin/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

> 由于grep命令自带--color=auto颜色标识，过滤出来自动标明。若使用绝对路径/usr/bin/grep则没有颜色标明。

# 行数-c #

[root@localhost grep]# grep -c 'nologin' passwd
    	15

# 显示行号-n #

# 不区分大小写-i #

> 将其中某一行改为大写

[root@localhost grep]# 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
    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
    21:systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
    22:php-fpm:x:1001:1001::/home/php-fpm:/sbin/nologin
    23:apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
    
    [root@localhost grep]# grep -ni '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
    21:systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
    22:php-fpm:x:1001:1001::/home/php-fpm:/sbin/nologin
    23:apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin

> 可以发现第9行，以-i过滤是不区分大小写

# 取反-v #

[root@localhost grep]# grep -v 'nologin' passwd
    	root:x:0:0:root:/root:/bin/bash
    	sync:x:5:0:sync:/sbin:/bin/sync
    	shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
    	halt:x:7:0:halt:/sbin:/sbin/halt
    	user1:x:1002:1002::/home/user1:/bin/bash
    	user2:x:1003:1003::/home/user2:/bin/bash
    [root@localhost grep]# grep -inv '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:user1:x:1002:1002::/home/user1:/bin/bash
    	21:user2:x:1003:1003::/home/user2:/bin/bash

> 过滤出来后将剩余的行显示出来

# 递归遍历所有子目录-r #

[root@localhost grep]# grep -r 'hello' /root/
    	/root/.bash_history:echo helloworld > 1.txt
    	/root/.bash_history:echo helloworld > 1.txt
    	/root/.bash_history:echo helloworld >> 1.txt
    	/root/.bash_history:echo helloworld 2> 1.txt
    	/root/.bash_history:hello=world
    	/root/.bash_history:echo $hello
    	/root/.bash_history:echo $hello
    	/root/.bash_history:echo $hello
    	/root/.bash_history:echo $hello
    	/root/.bash_history:export hello=world
    	/root/.bash_history:echo $hello
    	/root/.bash_history:echo $hello
    	/root/.bash_history:echo $hello
    	/root/.bash_history:unset hello
    	/root/.bash_history:echo $hello
    	/root/.bash_history:vi hello.sh
    	/root/.bash_history:chmod + x hello.sh
    	/root/.bash_history:chmod +x hello.sh
    	/root/.bash_history:sh hello.sh
    	/root/.bash_history:echo "helloworld" | tr '[hw]' '[HW]'
    	/root/.bash_history:echo "helloworld" | tr 'h' 'H'
    	/root/.bash_history:echo "helloworld" | tr '[a-z]' '[A-Z]'
    	/root/.bash_history:[ -d hello] || mkdir hello
    	/root/.bash_history:[ -d hello] || mkdir hello
    	/root/.bash_history:[ -d hello ] || mkdir hello
    	/root/.bash_history:[ -d hello ] && mkdir hello
    	/root/.bash_history:export hello=world
    	/root/.bash_history:echo $hello
    	/root/hello.sh:echo "hello!"

# 过滤出符合要求的行以及下面n行,-A+number #

[root@localhost grep]# grep 'root' /etc/passwd
    	root:x:0:0:root:/root:/bin/bash
    	operator:x:11:0:operator:/root:/sbin/nologin
    [root@localhost grep]# grep -A2 'root' /etc/passwd
    	root:x:0:0:root:/root:/bin/bash
    	bin:x:1:1:bin:/bin:/sbin/nologin
    	daemon:x:2:2:daemon:/sbin:/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

# 过滤出符合要求的行以及上面n行,-B+number #

[root@localhost grep]# grep -B2 'root' /etc/passwd
    	root:x:0:0:root:/root:/bin/bash
    	--
    	halt:x:7:0:halt:/sbin:/sbin/halt
    	mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
    	operator:x:11:0:operator:/root:/sbin/nologin

# 过滤出符合要求的行以及上下面n行,-C+number #

[root@localhost grep]# grep -C2 'root' /etc/passwd
    	root:x:0:0:root:/root:/bin/bash
    	bin:x:1:1:bin:/bin:/sbin/nologin
    	daemon:x:2:2:daemon:/sbin:/sbin/nologin
    	--
    	halt:x:7:0:halt:/sbin:/sbin/halt
    	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

*  'string' 单引号 (single quote) 被单引号用括住的内容，将被视为单一字串。在引号内的代表变数的$符号，没有作用，也就是说，他被视为一般符号处理，防止任何变量替换。 heyyou=homeecho '$heyyou' \# We get $heyyou
 *  "string" 双引号 (double quote) 被双引号用括住的内容，将被视为单一字串。它防止通配符扩展，但允许变量扩展。这点与单引数的处理方式不同。 heyyou=homeecho "$heyyou" \# We get home
 *  \`command\` 倒引号 (backticks) 在前面的单双引号，括住的是字串，但如果该字串是一列命令列，会怎样？答案是不会执行。要处理这种情况，我们得用倒单引号来做。 fdv=\`date +%F\`echo "Today $fdv" 在倒引号内的 date +%F 会被视为指令，执行的结果会带入 fdv 变数中

# \[0-9\] #

[root@localhost grep]# grep '[0-9]' passwd
    root:x:0:0:root:/root:/bin/bash
    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
    sync:x:5:0:sync:/sbin:/bin/sync
    shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
    halt:x:7:0:halt:/sbin:/sbin/halt
    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
    mysql:x:1000:1000::/home/mysql:/bin/bash
    systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
    php-fpm:x:1001:1001::/home/php-fpm:/sbin/nologin
    apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin

[root@localhost grep]# grep -nv '[0-9]' /etc/inittab 
    1:# inittab is no longer used when using systemd.
    2:#
    3:# ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
    4:#
    5:# Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target
    6:#
    7:# systemd uses 'targets' instead of runlevels. By default, there are two main targets:
    8:#
    11:#
    12:# To view current default target, run:
    13:# systemctl get-default
    14:#
    15:# To set a default target, run:
    16:# systemctl set-default TARGET.target
    17:#

# 以任意字符开头^+str #

[root@localhost grep]# cp /etc/inittab .
    [root@localhost grep]# cat passwd >> inittab
    [root@localhost grep]# grep -n '^#' inittab 
    1:# inittab is no longer used when using systemd.
    2:#
    3:# ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
    4:#
    5:# Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target
    6:#
    7:# systemd uses 'targets' instead of runlevels. By default, there are two main targets:
    8:#
    9:# multi-user.target: analogous to runlevel 3
    10:# graphical.target: analogous to runlevel 5
    11:#
    12:# To view current default target, run:
    13:# systemctl get-default
    14:#
    15:# To set a default target, run:
    16:# systemctl set-default TARGET.target
    17:#
    [root@localhost grep]# grep -vn '^#' inittab 
    18:root:x:0:0:root:/root:/bin/bash
    19:bin:x:1:1:bin:/bin:/sbin/nologin
    20:daemon:x:2:2:daemon:/sbin:/sbin/nologin
    21:adm:x:3:4:adm:/var/adm:/sbin/nologin
    22:lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
    23:sync:x:5:0:sync:/sbin:/bin/sync
    24:shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
    25:halt:x:7:0:halt:/sbin:/sbin/halt
    26:mail:x:8:12:mail:/var/spool/mail:/sbin/NOLogin
    27:operator:x:11:0:operator:/root:/sbin/nologin
    28:games:x:12:100:games:/usr/games:/sbin/nologin
    29:ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
    30:nobody:x:99:99:Nobody:/:/sbin/nologin
    31:dbus:x:81:81:System message bus:/:/sbin/nologin
    32:polkitd:x:999:998:User for polkitd:/:/sbin/nologin
    33:avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
    34:avahi-autoipd:x:170:170:Avahi IPv4LL Stack:/var/lib/avahi-autoipd:/sbin/nologin
    35:postfix:x:89:89::/var/spool/postfix:/sbin/nologin
    36:sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
    37:mysql:x:1000:1000::/home/mysql:/bin/bash
    38:systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
    39:php-fpm:x:1001:1001::/home/php-fpm:/sbin/nologin
    40:apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin

[root@localhost grep]# grep -vn '^#' inittab | grep -v '^3'
    18:root:x:0:0:root:/root:/bin/bash
    19:bin:x:1:1:bin:/bin:/sbin/nologin
    20:daemon:x:2:2:daemon:/sbin:/sbin/nologin
    21:adm:x:3:4:adm:/var/adm:/sbin/nologin
    22:lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
    23:sync:x:5:0:sync:/sbin:/bin/sync
    24:shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
    25:halt:x:7:0:halt:/sbin:/sbin/halt
    26:mail:x:8:12:mail:/var/spool/mail:/sbin/NOLogin
    27:operator:x:11:0:operator:/root:/sbin/nologin
    28:games:x:12:100:games:/usr/games:/sbin/nologin
    29:ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
    40:apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
    [root@localhost grep]# grep -vn '^#' inittab | grep -v '^[1-3]'
    40:apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin

# \[\]非0-9 #

[root@localhost grep]# grep '[0-9]' inittab 
    # multi-user.target: analogous to runlevel 3
    # graphical.target: analogous to runlevel 5
    root:x:0:0:root:/root:/bin/bash
    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
    sync:x:5:0:sync:/sbin:/bin/sync
    shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
    halt:x:7:0:halt:/sbin:/sbin/halt
    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
    mysql:x:1000:1000::/home/mysql:/bin/bash
    systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
    php-fpm:x:1001:1001::/home/php-fpm:/sbin/nologin
    apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
    [root@localhost grep]# grep '[^0-9]' inittab 
    # inittab is no longer used when using systemd.
    #
    # ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
    #
    # Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target
    #
    # systemd uses 'targets' instead of runlevels. By default, there are two main targets:
    #
    # multi-user.target: analogous to runlevel 3
    # graphical.target: analogous to runlevel 5
    #
    # To view current default target, run:
    # systemctl get-default
    #
    # To set a default target, run:
    # systemctl set-default TARGET.target
    #
    root:x:0:0:root:/root:/bin/bash
    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
    sync:x:5:0:sync:/sbin:/bin/sync
    shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
    halt:x:7:0:halt:/sbin:/sbin/halt
    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
    mysql:x:1000:1000::/home/mysql:/bin/bash
    systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
    php-fpm:x:1001:1001::/home/php-fpm:/sbin/nologin
    apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin

> 可以看到非0-9以外的字符都呈红色

[root@localhost grep]# grep '^[^0-9]' inittab 
    # inittab is no longer used when using systemd.
    #
    # ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
    #
    # Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target
    #
    # systemd uses 'targets' instead of runlevels. By default, there are two main targets:
    #
    # multi-user.target: analogous to runlevel 3
    # graphical.target: analogous to runlevel 5
    #
    # To view current default target, run:
    # systemctl get-default
    #
    # To set a default target, run:
    # systemctl set-default TARGET.target
    #
    root:x:0:0:root:/root:/bin/bash
    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
    sync:x:5:0:sync:/sbin:/bin/sync
    shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
    halt:x:7:0:halt:/sbin:/sbin/halt
    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
    mysql:x:1000:1000::/home/mysql:/bin/bash
    systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
    php-fpm:x:1001:1001::/home/php-fpm:/sbin/nologin
    apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin

> 以非0-9的任意字符开头

# \[a-zA-Z\] #

[root@localhost grep]# grep '^[^a-zA-Z]' inittab 
    # inittab is no longer used when using systemd.
    #
    # ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
    #
    # Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target
    #
    # systemd uses 'targets' instead of runlevels. By default, there are two main targets:
    #
    # multi-user.target: analogous to runlevel 3
    # graphical.target: analogous to runlevel 5
    #
    # To view current default target, run:
    # systemctl get-default
    #
    # To set a default target, run:
    # systemctl set-default TARGET.target
    #

# .任意一个字符 #

[root@localhost grep]# grep 'r.o' inittab 
    root:x:0:0:root:/root:/bin/bash
    operator:x:11:0:operator:/root:/sbin/nologin
    [root@localhost grep]# grep 'r..t' inittab 
    # Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target
    # systemd uses 'targets' instead of runlevels. By default, there are two main targets:
    # multi-user.target: analogous to runlevel 3
    # graphical.target: analogous to runlevel 5
    # To view current default target, run:
    # To set a default target, run:
    # systemctl set-default TARGET.target
    root:x:0:0:root:/root:/bin/bash
    operator:x:11:0:operator:/root:/sbin/nologin
    ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
    
    [root@localhost grep]# grep '/./' inittab 
    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
    systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
    [root@localhost grep]# grep '/../' inittab 
    [root@localhost grep]# grep '/.../' inittab 
    # Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target
    root:x:0:0:root:/root:/bin/bash
    adm:x:3:4:adm:/var/adm:/sbin/nologin
    lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
    sync:x:5:0:sync:/sbin:/bin/sync
    mail:x:8:12:mail:/var/spool/mail:/sbin/NOLogin
    games:x:12:100:games:/usr/games:/sbin/nologin
    ftp:x:14:50:FTP User:/var/ftp:/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
    mysql:x:1000:1000::/home/mysql:/bin/bash
    apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin

# \*零个或多个 #

[root@localhost grep]# grep 'ro*' inittab 
    # inittab is no longer used when using systemd.
    # Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target
    # systemd uses 'targets' instead of runlevels. By default, there are two main targets:
    # multi-user.target: analogous to runlevel 3
    # graphical.target: analogous to runlevel 5
    # To view current default target, run:
    # To set a default target, run:
    # systemctl set-default TARGET.target
    root:x:0:0:root:/root:/bin/bash
    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
    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
    systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
    apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
    [root@localhost grep]# grep 'roo*' inittab 
    root:x:0:0:root:/root:/bin/bash
    operator:x:11:0:operator:/root:/sbin/nologin

# .\*任意字符 #

[root@localhost grep]# grep '.*' inittab 
    # inittab is no longer used when using systemd.
    #
    # ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
    #
    # Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target
    #
    # systemd uses 'targets' instead of runlevels. By default, there are two main targets:
    #
    # multi-user.target: analogous to runlevel 3
    # graphical.target: analogous to runlevel 5
    #
    # To view current default target, run:
    # systemctl get-default
    #
    # To set a default target, run:
    # systemctl set-default TARGET.target
    #
    root:x:0:0:root:/root:/bin/bash
    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
    sync:x:5:0:sync:/sbin:/bin/sync
    shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
    halt:x:7:0:halt:/sbin:/sbin/halt
    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
    mysql:x:1000:1000::/home/mysql:/bin/bash
    systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
    php-fpm:x:1001:1001::/home/php-fpm:/sbin/nologin
    apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin

[root@localhost grep]# grep 'mysql.*bash' inittab 
    mysql:x:1000:1000::/home/mysql:/bin/bash
    [root@localhost grep]# grep 'mysql.*' inittab 
    mysql:x:1000:1000::/home/mysql:/bin/bash

# str+\{number\}匹配str重复的次数 #

[root@localhost grep]# grep 'o{2}' inittab
    
    [root@localhost grep]# grep 'o\{2\}' inittab 
    root:x:0:0:root:/root:/bin/bash
    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

> 若重复的次数为oooo也能匹配出来

# str+\{number,number\}匹配范围 #

[root@localhost grep]# grep '9\{1,3\}' inittab 
    nobody:x:99:99:Nobody:/:/sbin/nologin
    polkitd:x:999:998:User for polkitd:/:/sbin/nologin
    postfix:x:89:89::/var/spool/postfix:/sbin/nologin
    systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin

# egrep扩展 #

[root@localhost grep]# egrep '9{1,3}' inittab 
    nobody:x:99:99:Nobody:/:/sbin/nologin
    polkitd:x:999:998:User for polkitd:/:/sbin/nologin
    postfix:x:89:89::/var/spool/postfix:/sbin/nologin
    systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin

> 不需要反斜杠

# \-E同上 #

[root@localhost grep]# grep -E '9{1,3}' inittab 
    nobody:x:99:99:Nobody:/:/sbin/nologin
    polkitd:x:999:998:User for polkitd:/:/sbin/nologin
    postfix:x:89:89::/var/spool/postfix:/sbin/nologin
    systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin

# (str)\{number,number\} #

[root@localhost grep]# grep -E '(99){1,3}' inittab 
    nobody:x:99:99:Nobody:/:/sbin/nologin
    polkitd:x:999:998:User for polkitd:/:/sbin/nologin

# str+匹配一次或多次str #

[root@localhost grep]# grep 'o\+b' inittab 
    nobody:x:99:99:Nobody:/:/sbin/nologin
    [root@localhost grep]# grep 'o\+t' inittab 
    root:x:0:0:root:/root:/bin/bash
    operator:x:11:0:operator:/root:/sbin/nologin

# str?匹配零次或一次str #

[root@localhost grep]# 
    [root@localhost grep]# grep 'o\?t' inittab 
    # inittab is no longer used when using systemd.
    # Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target
    # systemd uses 'targets' instead of runlevels. By default, there are two main targets:
    # multi-user.target: analogous to runlevel 3
    # graphical.target: analogous to runlevel 5
    # To view current default target, run:
    # systemctl get-default
    # To set a default target, run:
    # systemctl set-default TARGET.target
    root:x:0:0:root:/root:/bin/bash
    shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
    halt:x:7:0:halt:/sbin:/sbin/halt
    operator:x:11:0:operator:/root:/sbin/nologin
    ftp:x:14:50:FTP User:/var/ftp:/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
    systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
    apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin

[root@localhost grep]# grep '70\?:' inittab 
    lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
    halt:x:7:0:halt:/sbin:/sbin/halt
    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@localhost grep]# grep '70\?:A' inittab 
    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

# str|str或者 #

[root@localhost grep]# grep 'root\|mysql' inittab 
    root:x:0:0:root:/root:/bin/bash
    operator:x:11:0:operator:/root:/sbin/nologin
    mysql:x:1000:1000::/home/mysql:/bin/bash
    
    [root@localhost grep]# grep 'root\|mysql' inittab 
    root:x:0:0:root:/root:/bin/bash
    operator:x:11:0:operator:/root:/sbin/nologin
    mysql:x:1000:1000::/home/mysql:/bin/bash
    [root@localhost grep]# grep 'root\|mysql\|nobody' inittab 
    root:x:0:0:root:/root:/bin/bash
    operator:x:11:0:operator:/root:/sbin/nologin
    nobody:x:99:99:Nobody:/:/sbin/nologin
    mysql:x:1000:1000::/home/mysql:/bin/bash

--------------------

转载于:https://my.oschina.net/u/3892756/blog/3056529

[2019_Python_]: https://my.oschina.net/u/2663968/blog/3061697
[hot3.png]: /images/20220113/e1fd2fdd24b5413f93abfedc5410e78c.png