六週第一次課

六週第一次課

9.1 正則介紹_grep上

9.2 grep中

9.3 grep下

9.1 正則介紹_grep上

本章是學習shell的基礎，本章學的越好，shell也就會學的越好。

在計算機科學中，正則表達式的含義是：它使用單個字符串來描述或匹配一系列符合某個句法規則的字符串。在許多文本編輯器或工具裏，正則表達式一般用來檢索和替換那些符合某個模式的文本內容。對系統管理員來講，正則表達式貫穿咱們的平常運維工做當中，不管是查找某個文檔，仍是查詢某個日誌文件並分析其內容，都會用到正則表達式。

其實正則表達式只是一種思想、一種表示方法。只要工具支持這種方法，這個工具就能夠處理正則表達式的字符串。經常使用的正則表達式有grep、sed、awk，它們都是針對文本的行來操做的。

什麼是正則？

• 正則就是一串有規律的字符串

這個字符串是有特殊符號的，好比.、*、!、?、()、{}、[]等等各類各樣的符號組合在一塊兒，造成了規律的字符串。這一章主要是講如何掌握好這些規律。

• 掌握好正則對於編寫shell腳本有很大幫助

不只是shelll，php、java、python等等裏面都是有正則的。

• 各類編程語言中都有正則，原理是同樣的

有了正則，就能夠實現不少複雜的需求。

• 本章將要學習grep/egrep、sed、awk

egrep是grep的擴展，grep能夠實現的功能，egrep均可以實現。

grep

grep是用來過濾指定關鍵詞的。

grep的格式以下：

• grep [-cinvABC] 'word' filename

• -c 行數

[root@localhost ~]# ls
123  1.txt  2.txt  3.txt  456  789  anaconda-ks.cfg.1  a.txt  bb.txt  initial-setup-ks.cfg  perl5
[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
ods:x:999:998:softhsm private keys owner:/var/lib/softhsm:/sbin/nologin
pegasus:x:66:65:tog-pegasus OpenPegasus WBEM/CIM services:/var/lib/Pegasus:/sbin/nologin
systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
polkitd:x:998:996:User for polkitd:/:/sbin/nologin
apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
tomcat:x:91:91:Apache Tomcat:/usr/share/tomcat:/sbin/nologin
colord:x:997:994:User for colord:/var/lib/colord:/sbin/nologin
abrt:x:173:173::/etc/abrt:/sbin/nologin
saslauth:x:996:76:Saslauthd user:/run/saslauthd:/sbin/nologin
libstoragemgmt:x:995:993:daemon account for libstoragemgmt:/var/run/lsm:/sbin/nologin
dirsrv:x:389:389:user for 389-ds-base:/usr/share/dirsrv:/sbin/nologin
rpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin
hsqldb:x:96:96::/var/lib/hsqldb:/sbin/nologin
unbound:x:388:388:Unbound DNS resolver:/etc/unbound:/sbin/nologin
pkiuser:x:17:17:Certificate System:/usr/share/pki:/sbin/nologin
setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
rtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin
pulse:x:171:171:PulseAudio System Daemon:/var/run/pulse:/sbin/nologin
qemu:x:107:107:qemu user:/:/sbin/nologin
ntp:x:38:38::/etc/ntp:/sbin/nologin
radvd:x:75:75:radvd user:/:/sbin/nologin
chrony:x:386:384::/var/lib/chrony:/sbin/nologin
named:x:25:25:Named:/var/named:/sbin/nologin
mysql:x:27:27:MariaDB Server:/var/lib/mysql:/sbin/nologin
tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin
usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin
geoclue:x:385:382:User for geoclue:/var/lib/geoclue:/sbin/nologin
sssd:x:384:381:User for sssd:/:/sbin/nologin
gdm:x:42:42::/var/lib/gdm:/sbin/nologin
rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin
nfsnobody:x:65534:65534:Anonymous NFS User:/var/lib/nfs:/sbin/nologin
pcp:x:383:380:Performance Co-Pilot:/var/lib/pcp:/sbin/nologin
kdcproxy:x:382:379:IPA KDC Proxy User:/:/sbin/nologin
ipaapi:x:381:378:IPA Framework User:/:/sbin/nologin
gnome-initial-setup:x:380:377::/run/gnome-initial-setup/:/sbin/nologin
avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
dovecot:x:97:97:Dovecot IMAP server:/usr/libexec/dovecot:/sbin/nologin
dovenull:x:379:376:Dovecot's unauthorized user:/usr/libexec/dovecot:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
oprofile:x:16:16:Special user account to be used by OProfile:/var/lib/oprofile:/sbin/nologin
tcpdump:x:72:72::/:/sbin/nologin
[root@localhost grep]# 

注：在CentOS 7中，grep默認幫咱們把匹配到的字符串標註了紅色。用which命令查看grep，能夠看到grep其實就是grep --color=auto，這個選項就是顏色表示。

[root@localhost grep]# which grep
alias grep='grep --color=auto'
    /usr/bin/grep
[root@localhost grep]# 

在CentOS 6中是沒有顏色顯示的，經過命令能夠查看。

[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
ods:x:999:998:softhsm private keys owner:/var/lib/softhsm:/sbin/nologin
pegasus:x:66:65:tog-pegasus OpenPegasus WBEM/CIM services:/var/lib/Pegasus:/sbin/nologin
systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
polkitd:x:998:996:User for polkitd:/:/sbin/nologin
apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
tomcat:x:91:91:Apache Tomcat:/usr/share/tomcat:/sbin/nologin
colord:x:997:994:User for colord:/var/lib/colord:/sbin/nologin
abrt:x:173:173::/etc/abrt:/sbin/nologin
saslauth:x:996:76:Saslauthd user:/run/saslauthd:/sbin/nologin
libstoragemgmt:x:995:993:daemon account for libstoragemgmt:/var/run/lsm:/sbin/nologin
dirsrv:x:389:389:user for 389-ds-base:/usr/share/dirsrv:/sbin/nologin
rpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin
hsqldb:x:96:96::/var/lib/hsqldb:/sbin/nologin
unbound:x:388:388:Unbound DNS resolver:/etc/unbound:/sbin/nologin
pkiuser:x:17:17:Certificate System:/usr/share/pki:/sbin/nologin
setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
rtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin
pulse:x:171:171:PulseAudio System Daemon:/var/run/pulse:/sbin/nologin
qemu:x:107:107:qemu user:/:/sbin/nologin
ntp:x:38:38::/etc/ntp:/sbin/nologin
radvd:x:75:75:radvd user:/:/sbin/nologin
chrony:x:386:384::/var/lib/chrony:/sbin/nologin
named:x:25:25:Named:/var/named:/sbin/nologin
mysql:x:27:27:MariaDB Server:/var/lib/mysql:/sbin/nologin
tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin
usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin
geoclue:x:385:382:User for geoclue:/var/lib/geoclue:/sbin/nologin
sssd:x:384:381:User for sssd:/:/sbin/nologin
gdm:x:42:42::/var/lib/gdm:/sbin/nologin
rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin
nfsnobody:x:65534:65534:Anonymous NFS User:/var/lib/nfs:/sbin/nologin
pcp:x:383:380:Performance Co-Pilot:/var/lib/pcp:/sbin/nologin
kdcproxy:x:382:379:IPA KDC Proxy User:/:/sbin/nologin
ipaapi:x:381:378:IPA Framework User:/:/sbin/nologin
gnome-initial-setup:x:380:377::/run/gnome-initial-setup/:/sbin/nologin
avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
dovecot:x:97:97:Dovecot IMAP server:/usr/libexec/dovecot:/sbin/nologin
dovenull:x:379:376:Dovecot's unauthorized user:/usr/libexec/dovecot:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
oprofile:x:16:16:Special user account to be used by OProfile:/var/lib/oprofile:/sbin/nologin
tcpdump:x:72:72::/:/sbin/nologin
[root@localhost grep]# 

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

• -n 顯示行號

[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
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:ods:x:999:998:softhsm private keys owner:/var/lib/softhsm:/sbin/nologin
15:pegasus:x:66:65:tog-pegasus OpenPegasus WBEM/CIM services:/var/lib/Pegasus:/sbin/nologin
16:systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
17:dbus:x:81:81:System message bus:/:/sbin/nologin
18:polkitd:x:998:996:User for polkitd:/:/sbin/nologin
19:apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
20:tomcat:x:91:91:Apache Tomcat:/usr/share/tomcat:/sbin/nologin
21:colord:x:997:994:User for colord:/var/lib/colord:/sbin/nologin
22:abrt:x:173:173::/etc/abrt:/sbin/nologin
23:saslauth:x:996:76:Saslauthd user:/run/saslauthd:/sbin/nologin
24:libstoragemgmt:x:995:993:daemon account for libstoragemgmt:/var/run/lsm:/sbin/nologin
25:dirsrv:x:389:389:user for 389-ds-base:/usr/share/dirsrv:/sbin/nologin
26:rpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin
27:hsqldb:x:96:96::/var/lib/hsqldb:/sbin/nologin
28:unbound:x:388:388:Unbound DNS resolver:/etc/unbound:/sbin/nologin
30:pkiuser:x:17:17:Certificate System:/usr/share/pki:/sbin/nologin
31:setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
32:postfix:x:89:89::/var/spool/postfix:/sbin/nologin
33:rtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin
34:pulse:x:171:171:PulseAudio System Daemon:/var/run/pulse:/sbin/nologin
35:qemu:x:107:107:qemu user:/:/sbin/nologin
36:ntp:x:38:38::/etc/ntp:/sbin/nologin
37:radvd:x:75:75:radvd user:/:/sbin/nologin
38:chrony:x:386:384::/var/lib/chrony:/sbin/nologin
39:named:x:25:25:Named:/var/named:/sbin/nologin
40:mysql:x:27:27:MariaDB Server:/var/lib/mysql:/sbin/nologin
41:tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin
42:usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin
43:geoclue:x:385:382:User for geoclue:/var/lib/geoclue:/sbin/nologin
44:sssd:x:384:381:User for sssd:/:/sbin/nologin
45:gdm:x:42:42::/var/lib/gdm:/sbin/nologin
46:rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin
47:nfsnobody:x:65534:65534:Anonymous NFS User:/var/lib/nfs:/sbin/nologin
48:pcp:x:383:380:Performance Co-Pilot:/var/lib/pcp:/sbin/nologin
49:kdcproxy:x:382:379:IPA KDC Proxy User:/:/sbin/nologin
50:ipaapi:x:381:378:IPA Framework User:/:/sbin/nologin
51:gnome-initial-setup:x:380:377::/run/gnome-initial-setup/:/sbin/nologin
52:avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
54:dovecot:x:97:97:Dovecot IMAP server:/usr/libexec/dovecot:/sbin/nologin
55:dovenull:x:379:376:Dovecot's unauthorized user:/usr/libexec/dovecot:/sbin/nologin
56:sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
57:oprofile:x:16:16:Special user account to be used by OProfile:/var/lib/oprofile:/sbin/nologin
58:tcpdump:x:72:72::/:/sbin/nologin
[root@localhost grep]# 

• -i 不區分大小寫

[root@localhost grep]# vim passwd

root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/NOlogin        #這裏nologin改爲NOlogin

[root@localhost grep]# grep -ni 'nologin' passwd
2:bin:x:1:1:bin:/bin:/sbin/NOlogin    #這裏會把大寫的顯示出來，是不區分大小寫的
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:ods:x:999:998:softhsm private keys owner:/var/lib/softhsm:/sbin/nologin
15:pegasus:x:66:65:tog-pegasus OpenPegasus WBEM/CIM services:/var/lib/Pegasus:/sbin/nologin
16:systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
17:dbus:x:81:81:System message bus:/:/sbin/nologin
18:polkitd:x:998:996:User for polkitd:/:/sbin/nologin
19:apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
20:tomcat:x:91:91:Apache Tomcat:/usr/share/tomcat:/sbin/nologin
21:colord:x:997:994:User for colord:/var/lib/colord:/sbin/nologin
22:abrt:x:173:173::/etc/abrt:/sbin/nologin
23:saslauth:x:996:76:Saslauthd user:/run/saslauthd:/sbin/nologin
24:libstoragemgmt:x:995:993:daemon account for libstoragemgmt:/var/run/lsm:/sbin/nologin
25:dirsrv:x:389:389:user for 389-ds-base:/usr/share/dirsrv:/sbin/nologin
26:rpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin
27:hsqldb:x:96:96::/var/lib/hsqldb:/sbin/nologin
28:unbound:x:388:388:Unbound DNS resolver:/etc/unbound:/sbin/nologin
30:pkiuser:x:17:17:Certificate System:/usr/share/pki:/sbin/nologin
31:setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
32:postfix:x:89:89::/var/spool/postfix:/sbin/nologin
33:rtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin
34:pulse:x:171:171:PulseAudio System Daemon:/var/run/pulse:/sbin/nologin
35:qemu:x:107:107:qemu user:/:/sbin/nologin
36:ntp:x:38:38::/etc/ntp:/sbin/nologin
37:radvd:x:75:75:radvd user:/:/sbin/nologin
38:chrony:x:386:384::/var/lib/chrony:/sbin/nologin
39:named:x:25:25:Named:/var/named:/sbin/nologin
40:mysql:x:27:27:MariaDB Server:/var/lib/mysql:/sbin/nologin
41:tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin
42:usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin
43:geoclue:x:385:382:User for geoclue:/var/lib/geoclue:/sbin/nologin
44:sssd:x:384:381:User for sssd:/:/sbin/nologin
45:gdm:x:42:42::/var/lib/gdm:/sbin/nologin
46:rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin
47:nfsnobody:x:65534:65534:Anonymous NFS User:/var/lib/nfs:/sbin/nologin
48:pcp:x:383:380:Performance Co-Pilot:/var/lib/pcp:/sbin/nologin
49:kdcproxy:x:382:379:IPA KDC Proxy User:/:/sbin/nologin
50:ipaapi:x:381:378:IPA Framework User:/:/sbin/nologin
51:gnome-initial-setup:x:380:377::/run/gnome-initial-setup/:/sbin/nologin
52:avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
54:dovecot:x:97:97:Dovecot IMAP server:/usr/libexec/dovecot:/sbin/nologin
55:dovenull:x:379:376:Dovecot's unauthorized user:/usr/libexec/dovecot:/sbin/nologin
56:sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
57:oprofile:x:16:16:Special user account to be used by OProfile:/var/lib/oprofile:/sbin/nologin
58:tcpdump:x:72:72::/:/sbin/nologin
[root@localhost grep]# 

• -v 取反

[root@localhost grep]# 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
29:amandabackup:x:33:6:Amanda user:/var/lib/amanda:/bin/bash
53:postgres:x:26:26:PostgreSQL Server:/var/lib/pgsql:/bin/bash
59:tianqi:x:1000:1000:tianqi:/home/tianqi:/bin/bash
60:aming:x:1001:1001::/home/aming:/bin/bash
61:user1:x:1002:1002::/home/user1:/bin/bash
[root@localhost grep]# 

把不帶nologin的行過濾出來

• -r把子目錄和孫目錄下面的文件所有遍歷一遍

[root@localhost grep]# grep -r 'root' /etc
/etc/X11/xinit/Xclients:rm -f $HOME/Xrootenv.0
/etc/X11/xinit/Xclients:    [ -x /usr/bin/xsetroot ] && /usr/bin/xsetroot -solid '#222E45'
/etc/X11/xinit/xinitrc:    [ -x /usr/bin/xsetroot ] && /usr/bin/xsetroot -solid '#222E45'
/etc/X11/xinit/xinitrc.d/zz-liveinst.sh:[ -x /usr/bin/xhost ] && xhost +si:localuser:root > /dev/null 2>&1
/etc/X11/mwm/system.mwmrc:    Alt<Key>Tab        root|icon|window    f.next_key
/etc/X11/mwm/system.mwmrc:    Alt Shift<Key>Tab    root|icon|window    f.prev_key
/etc/X11/mwm/system.mwmrc:    Alt<Key>Escape        root|icon|window    f.circle_down
/etc/X11/mwm/system.mwmrc:    Alt Shift<Key>Escape    root|icon|window    f.circle_up
/etc/X11/mwm/system.mwmrc:    Alt Shift Ctrl<Key>exclam root|icon|window    f.set_behavior
/etc/X11/mwm/system.mwmrc:!    Alt Shift<Key>Delete    root|icon|window    f.restart
/etc/X11/mwm/system.mwmrc:    <Btn3Down>    root        f.menu    DefaultRootMenu
/etc/X11/mwm/system.mwmrc:    <Btn3Down>    

下面的文件很是之多

若是不加-r選項

[root@localhost grep]# grep 'root' /etc
grep: /etc: Is a directory
[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]# 

加-r選項，找出的內容很是之多，能夠重定向到一個文件中去。

[root@localhost grep]# grep -r 'root' /etc > /tmp/grep.log
[root@localhost grep]# grep 'passwd' /tmp/grep.log
/etc/passwd:root:x:0:0:root:/root:/bin/bash
/etc/passwd:operator:x:11:0:operator:/root:/sbin/nologin
/etc/postfix/main.cf:# the system passwd file in the chroot jail is just not practical.
/etc/passwd-:root:x:0:0:root:/root:/bin/bash
/etc/passwd-:operator:x:11:0:operator:/root:/sbin/nologin
[root@localhost grep]# 

• -A 後面跟數字，過濾出符合要求的行以及下面n行

[root@localhost grep]# grep -A2 'root' 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
[root@localhost grep]# 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@localhost grep]# 

將包含關鍵字root的行，以及它下面的2行列出來。

• -B 同上，過濾出符合要求的行以及上面n行

[root@localhost grep]# 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@localhost grep]#

將包含關鍵字root的行，以及它上面的2行列出來。

• -C 同上，同時過濾出符合要求的行以及上下各n行

[root@localhost grep]# 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@localhost grep]# 

將包含關鍵字root的行，以及它的上下2行列出來。

9.2 grep中

方括號[ ]：匹配方括號裏任意一個字符

[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
ods:x:999:998:softhsm private keys owner:/var/lib/softhsm:/sbin/nologin
pegasus:x:66:65:tog-pegasus OpenPegasus WBEM/CIM services:/var/lib/Pegasus:/sbin/nologin
systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
polkitd:x:998:996:User for polkitd:/:/sbin/nologin
apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
tomcat:x:91:91:Apache Tomcat:/usr/share/tomcat:/sbin/nologin
colord:x:997:994:User for colord:/var/lib/colord:/sbin/nologin
abrt:x:173:173::/etc/abrt:/sbin/nologin
saslauth:x:996:76:Saslauthd user:/run/saslauthd:/sbin/nologin
libstoragemgmt:x:995:993:daemon account for libstoragemgmt:/var/run/lsm:/sbin/nologin
dirsrv:x:389:389:user for 389-ds-base:/usr/share/dirsrv:/sbin/nologin
rpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin
hsqldb:x:96:96::/var/lib/hsqldb:/sbin/nologin
unbound:x:388:388:Unbound DNS resolver:/etc/unbound:/sbin/nologin
amandabackup:x:33:6:Amanda user:/var/lib/amanda:/bin/bash
pkiuser:x:17:17:Certificate System:/usr/share/pki:/sbin/nologin
setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
rtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin
pulse:x:171:171:PulseAudio System Daemon:/var/run/pulse:/sbin/nologin
qemu:x:107:107:qemu user:/:/sbin/nologin
ntp:x:38:38::/etc/ntp:/sbin/nologin
radvd:x:75:75:radvd user:/:/sbin/nologin
chrony:x:386:384::/var/lib/chrony:/sbin/nologin
named:x:25:25:Named:/var/named:/sbin/nologin
mysql:x:27:27:MariaDB Server:/var/lib/mysql:/sbin/nologin
tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin
usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin
geoclue:x:385:382:User for geoclue:/var/lib/geoclue:/sbin/nologin
sssd:x:384:381:User for sssd:/:/sbin/nologin
gdm:x:42:42::/var/lib/gdm:/sbin/nologin
rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin
nfsnobody:x:65534:65534:Anonymous NFS User:/var/lib/nfs:/sbin/nologin
pcp:x:383:380:Performance Co-Pilot:/var/lib/pcp:/sbin/nologin
kdcproxy:x:382:379:IPA KDC Proxy User:/:/sbin/nologin
ipaapi:x:381:378:IPA Framework User:/:/sbin/nologin
gnome-initial-setup:x:380:377::/run/gnome-initial-setup/:/sbin/nologin
avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
postgres:x:26:26:PostgreSQL Server:/var/lib/pgsql:/bin/bash
dovecot:x:97:97:Dovecot IMAP server:/usr/libexec/dovecot:/sbin/nologin
dovenull:x:379:376:Dovecot's unauthorized user:/usr/libexec/dovecot:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
oprofile:x:16:16:Special user account to be used by OProfile:/var/lib/oprofile:/sbin/nologin
tcpdump:x:72:72::/:/sbin/nologin
tianqi:x:1000:1000:tianqi:/home/tianqi:/bin/bash
aming:x:1001:1001::/home/aming:/bin/bash
user1:x:1002:1002::/home/user1:/bin/bash
[root@localhost grep]# 

把passwd文件中不帶0-9數字的行過濾出來。

[root@localhost grep]# grep -v '[0-9]' passwd
[root@localhost grep]# 

結果代表，passwd文件中全部行都帶數字。

[root@localhost grep]# grep -v '[0-9]' /etc/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:
#
#
# To view current default target, run:
# systemctl get-default
#
# To set a default target, run:
# systemctl set-default TARGET.target
#
[root@localhost grep]# 

[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:#
[root@localhost grep]#

第9行和第10行沒有顯示，能夠看一下第9行和第10行的內容，實驗證實這兩行是帶數字的。

[root@localhost grep]# cat -n /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    #
     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]# 

^x：匹配以x開頭的字符

[root@localhost grep]# grep -n '^#' /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:#
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]# 

實驗證實全部的行開頭都帶#，將這個文件複製到當前目錄並做一下改動。

[root@localhost grep]# cp /etc/inittab .
[root@localhost grep]# vim /etc/inittab
[root@localhost grep]# vim /etc/inittab

這個文件輕易不要改動，由於它是系統的配置文件，能夠改複製過來的文件。

[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
15:#
16:# To set a default target, run:
17:# systemctl set-default TARGET.target
18:#
[root@localhost grep]# 

發現剛纔改動的第14行沒有顯示出來，下面能夠加-v將第14行過濾出來。

[root@localhost grep]# grep -nv '^#' inittab
14:abdgdegd
[root@localhost grep]# 

對inittab文件作一下修改，注意：千萬不要改動/etc/下的配置文件，一旦改動，系統可能不啓動

[root@localhost grep]# vim 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
aaaaa
#
# To view current default target, run:
# systemctl get-default
abdgdegd
#
# To set a default target, run:
11111111
# systemctl set-default TARGET.target

[root@localhost grep]# grep -v '^#' inittab
&*&(*&(*&*
aaaaa
abdgdegd
11111111
[root@localhost grep]# grep -vn '^#' inittab
8:&*&(*&(*&*
12:aaaaa
16:abdgdegd
19:11111111
[root@localhost grep]# 

 

[^xyz]：非，匹配除方括號裏xyz以外的任意字符串

[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
aaaaa
#
# To view current default target, run:
# systemctl get-default
abdgdegd
#
# To set a default target, run:
# systemctl set-default TARGET.target
#
[root@localhost grep]# 

只要有一個不是數字0-9的字符，就能夠過濾出來。

[root@localhost grep]# vim 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:
&*&(*&(*&*
#
111111111111a22222222222222
# multi-user.target: analogous to runlevel 3
# graphical.target: analogous to runlevel 5
aaaaa
#
# To view current default target, run:
# systemctl get-default
abdgdegd
#
# To set a default target, run:
11111111
# systemctl set-default TARGET.target

修改一下inittab文件，在中間添加一行111111111111a22222222222222。

[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:
&*&(*&(*&*
#
111111111111a22222222222222        #之間只有一個a不是數字，也顯示出了這同樣
# multi-user.target: analogous to runlevel 3
# graphical.target: analogous to runlevel 5
aaaaa
#
# To view current default target, run:
# systemctl get-default
abdgdegd
#
# To set a default target, run:
# systemctl set-default TARGET.target
#
[root@localhost grep]# 

^[^xyz]：匹配以除方括號裏xyz以外的任意字符開頭的字符

下面把以非數字開頭的行過濾出來

[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
aaaaa
#
# To view current default target, run:
# systemctl get-default
abdgdegd
#
# To set a default target, run:
# systemctl set-default TARGET.target
#
[root@localhost grep]# 

那以數字開頭的行都有哪些呢?

[root@localhost grep]# grep -v '^[^0-9]' inittab
111111111111a22222222222222
11111111
[root@localhost grep]# 

[root@localhost grep]# grep -nv '^[^0-9]' inittab
10:111111111111a22222222222222
20:11111111
[root@localhost grep]# 

[root@localhost grep]# grep -n '^[^0-9]' 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:#
11:# multi-user.target: analogous to runlevel 3
12:# graphical.target: analogous to runlevel 5
13:aaaaa
14:#
15:# To view current default target, run:
16:# systemctl get-default
17:abdgdegd
18:#
19:# To set a default target, run:
21:# systemctl set-default TARGET.target
22:#
[root@localhost grep]# 

能夠看到，沒有第10行，也沒有第20行。

注：^是以什麼開頭的意思，^放到[]裏面是取非的意思。

9.3 grep下

 

點 .：匹配任意一個字符，.自己也是能夠匹配到的

[root@localhost grep]# grep 'r.o' passwd
root:x:0:0:root:/root:/bin/bash
operator:x:11:0:operator:/root:/sbin/nologin
pcp:x:383:380:Performance Co-Pilot:/var/lib/pcp:/sbin/nologin
[root@localhost grep]# 

 

*：匹配星號左邊的字符重複0到n次的字符串。

[root@localhost grep]# grep 'o*o' 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
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
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
ods:x:999:998:softhsm private keys owner:/var/lib/softhsm:/sbin/nologin
pegasus:x:66:65:tog-pegasus OpenPegasus WBEM/CIM services:/var/lib/Pegasus:/sbin/nologin
systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
polkitd:x:998:996:User for polkitd:/:/sbin/nologin
apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
tomcat:x:91:91:Apache Tomcat:/usr/share/tomcat:/sbin/nologin
colord:x:997:994:User for colord:/var/lib/colord:/sbin/nologin
abrt:x:173:173::/etc/abrt:/sbin/nologin
saslauth:x:996:76:Saslauthd user:/run/saslauthd:/sbin/nologin
libstoragemgmt:x:995:993:daemon account for libstoragemgmt:/var/run/lsm:/sbin/nologin
dirsrv:x:389:389:user for 389-ds-base:/usr/share/dirsrv:/sbin/nologin
rpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin
hsqldb:x:96:96::/var/lib/hsqldb:/sbin/nologin
unbound:x:388:388:Unbound DNS resolver:/etc/unbound:/sbin/nologin
pkiuser:x:17:17:Certificate System:/usr/share/pki:/sbin/nologin
setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
rtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin
pulse:x:171:171:PulseAudio System Daemon:/var/run/pulse:/sbin/nologin
qemu:x:107:107:qemu user:/:/sbin/nologin
ntp:x:38:38::/etc/ntp:/sbin/nologin
radvd:x:75:75:radvd user:/:/sbin/nologin
chrony:x:386:384::/var/lib/chrony:/sbin/nologin
named:x:25:25:Named:/var/named:/sbin/nologin
mysql:x:27:27:MariaDB Server:/var/lib/mysql:/sbin/nologin
tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin
usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin
geoclue:x:385:382:User for geoclue:/var/lib/geoclue:/sbin/nologin
sssd:x:384:381:User for sssd:/:/sbin/nologin
gdm:x:42:42::/var/lib/gdm:/sbin/nologin
rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin
nfsnobody:x:65534:65534:Anonymous NFS User:/var/lib/nfs:/sbin/nologin
pcp:x:383:380:Performance Co-Pilot:/var/lib/pcp:/sbin/nologin
kdcproxy:x:382:379:IPA KDC Proxy User:/:/sbin/nologin
ipaapi:x:381:378:IPA Framework User:/:/sbin/nologin
gnome-initial-setup:x:380:377::/run/gnome-initial-setup/:/sbin/nologin
avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
postgres:x:26:26:PostgreSQL Server:/var/lib/pgsql:/bin/bash
dovecot:x:97:97:Dovecot IMAP server:/usr/libexec/dovecot:/sbin/nologin
dovenull:x:379:376:Dovecot's unauthorized user:/usr/libexec/dovecot:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
oprofile:x:16:16:Special user account to be used by OProfile:/var/lib/oprofile:/sbin/nologin
tcpdump:x:72:72::/:/sbin/nologin
tianqi:x:1000:1000:tianqi:/home/tianqi:/bin/bash
aming:x:1001:1001::/home/aming:/bin/bash
user1:x:1002:1002::/home/user1:/bin/bash
[root@localhost grep]# 

.*：表示零個或多個任意字符，空行也包含再內。會把passwd文件裏面的全部行都匹配到。

[root@localhost grep]# grep '.*' 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
ods:x:999:998:softhsm private keys owner:/var/lib/softhsm:/sbin/nologin
pegasus:x:66:65:tog-pegasus OpenPegasus WBEM/CIM services:/var/lib/Pegasus:/sbin/nologin
systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
polkitd:x:998:996:User for polkitd:/:/sbin/nologin
apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
tomcat:x:91:91:Apache Tomcat:/usr/share/tomcat:/sbin/nologin
colord:x:997:994:User for colord:/var/lib/colord:/sbin/nologin
abrt:x:173:173::/etc/abrt:/sbin/nologin
saslauth:x:996:76:Saslauthd user:/run/saslauthd:/sbin/nologin
libstoragemgmt:x:995:993:daemon account for libstoragemgmt:/var/run/lsm:/sbin/nologin
dirsrv:x:389:389:user for 389-ds-base:/usr/share/dirsrv:/sbin/nologin
rpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin
hsqldb:x:96:96::/var/lib/hsqldb:/sbin/nologin
unbound:x:388:388:Unbound DNS resolver:/etc/unbound:/sbin/nologin
amandabackup:x:33:6:Amanda user:/var/lib/amanda:/bin/bash
pkiuser:x:17:17:Certificate System:/usr/share/pki:/sbin/nologin
setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
rtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin
pulse:x:171:171:PulseAudio System Daemon:/var/run/pulse:/sbin/nologin
qemu:x:107:107:qemu user:/:/sbin/nologin
ntp:x:38:38::/etc/ntp:/sbin/nologin
radvd:x:75:75:radvd user:/:/sbin/nologin
chrony:x:386:384::/var/lib/chrony:/sbin/nologin
named:x:25:25:Named:/var/named:/sbin/nologin
mysql:x:27:27:MariaDB Server:/var/lib/mysql:/sbin/nologin
tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin
usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin
geoclue:x:385:382:User for geoclue:/var/lib/geoclue:/sbin/nologin
sssd:x:384:381:User for sssd:/:/sbin/nologin
gdm:x:42:42::/var/lib/gdm:/sbin/nologin
rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin
nfsnobody:x:65534:65534:Anonymous NFS User:/var/lib/nfs:/sbin/nologin
pcp:x:383:380:Performance Co-Pilot:/var/lib/pcp:/sbin/nologin
kdcproxy:x:382:379:IPA KDC Proxy User:/:/sbin/nologin
ipaapi:x:381:378:IPA Framework User:/:/sbin/nologin
gnome-initial-setup:x:380:377::/run/gnome-initial-setup/:/sbin/nologin
avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
postgres:x:26:26:PostgreSQL Server:/var/lib/pgsql:/bin/bash
dovecot:x:97:97:Dovecot IMAP server:/usr/libexec/dovecot:/sbin/nologin
dovenull:x:379:376:Dovecot's unauthorized user:/usr/libexec/dovecot:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
oprofile:x:16:16:Special user account to be used by OProfile:/var/lib/oprofile:/sbin/nologin
tcpdump:x:72:72::/:/sbin/nologin
tianqi:x:1000:1000:tianqi:/home/tianqi:/bin/bash
aming:x:1001:1001::/home/aming:/bin/bash
user1:x:1002:1002::/home/user1:/bin/bash
[root@localhost grep]# 

若是想匹配aming:x:1001:1001::/home/aming:/bin/bash這一行，可使用以下命令。

[root@localhost grep]# grep 'aming.*bash' passwd
aming:x:1001:1001::/home/aming:/bin/bash
[root@localhost grep]# 

花括號 x\{ n\}：字符x重複n次。脫義符號是把它本來的意思去掉。

[root@localhost grep]# grep 'o\{2\}' passwd
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
setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
[root@localhost grep]# 

x\{ n,m\}：字符x重複n到m次前面的字符，m也能夠爲空，這是表示大於等於m次。

[root@localhost grep]# grep 'o\{0,3\}' 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
ods:x:999:998:softhsm private keys owner:/var/lib/softhsm:/sbin/nologin
pegasus:x:66:65:tog-pegasus OpenPegasus WBEM/CIM services:/var/lib/Pegasus:/sbin/nologin
systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
polkitd:x:998:996:User for polkitd:/:/sbin/nologin
apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
tomcat:x:91:91:Apache Tomcat:/usr/share/tomcat:/sbin/nologin
colord:x:997:994:User for colord:/var/lib/colord:/sbin/nologin
abrt:x:173:173::/etc/abrt:/sbin/nologin
saslauth:x:996:76:Saslauthd user:/run/saslauthd:/sbin/nologin
libstoragemgmt:x:995:993:daemon account for libstoragemgmt:/var/run/lsm:/sbin/nologin
dirsrv:x:389:389:user for 389-ds-base:/usr/share/dirsrv:/sbin/nologin
rpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin
hsqldb:x:96:96::/var/lib/hsqldb:/sbin/nologin
unbound:x:388:388:Unbound DNS resolver:/etc/unbound:/sbin/nologin
amandabackup:x:33:6:Amanda user:/var/lib/amanda:/bin/bash
pkiuser:x:17:17:Certificate System:/usr/share/pki:/sbin/nologin
setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
rtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin
pulse:x:171:171:PulseAudio System Daemon:/var/run/pulse:/sbin/nologin
qemu:x:107:107:qemu user:/:/sbin/nologin
ntp:x:38:38::/etc/ntp:/sbin/nologin
radvd:x:75:75:radvd user:/:/sbin/nologin
chrony:x:386:384::/var/lib/chrony:/sbin/nologin
named:x:25:25:Named:/var/named:/sbin/nologin
mysql:x:27:27:MariaDB Server:/var/lib/mysql:/sbin/nologin
tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin
usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin
geoclue:x:385:382:User for geoclue:/var/lib/geoclue:/sbin/nologin
sssd:x:384:381:User for sssd:/:/sbin/nologin
gdm:x:42:42::/var/lib/gdm:/sbin/nologin
rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin
nfsnobody:x:65534:65534:Anonymous NFS User:/var/lib/nfs:/sbin/nologin
pcp:x:383:380:Performance Co-Pilot:/var/lib/pcp:/sbin/nologin
kdcproxy:x:382:379:IPA KDC Proxy User:/:/sbin/nologin
ipaapi:x:381:378:IPA Framework User:/:/sbin/nologin
gnome-initial-setup:x:380:377::/run/gnome-initial-setup/:/sbin/nologin
avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
postgres:x:26:26:PostgreSQL Server:/var/lib/pgsql:/bin/bash
dovecot:x:97:97:Dovecot IMAP server:/usr/libexec/dovecot:/sbin/nologin
dovenull:x:379:376:Dovecot's unauthorized user:/usr/libexec/dovecot:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
oprofile:x:16:16:Special user account to be used by OProfile:/var/lib/oprofile:/sbin/nologin
tcpdump:x:72:72::/:/sbin/nologin
tianqi:x:1000:1000:tianqi:/home/tianqi:/bin/bash
aming:x:1001:1001::/home/aming:/bin/bash
user1:x:1002:1002::/home/user1:/bin/bash
[root@localhost grep]# 

egrep：是grep的擴展版本，能夠完成grep不能完成的工做，能夠不使用字符 \

[root@localhost grep]# egrep 'o{2}' passwd
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
setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
[root@localhost grep]#

grep –E 跟egrep使用效果同樣

[root@localhost grep]# grep -E 'o{2}' passwd
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
setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
[root@localhost grep]# 

若是想出現4個o，可使用以下命令（將oo看做一個總體）

[root@localhost grep]# grep -E '(oo){2}' passwd
[root@localhost grep]# 

+：匹配加號左邊的字符重複1到n次的字符串。

使用+要使用脫義符號，不想使用脫義符號，可使用egrep或者grep-E

[root@localhost grep]# grep 'o\+o' passwd
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
setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
[root@localhost grep]# grep -E 'o+o' passwd
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
setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
[root@localhost grep]# egrep 'o+o' passwd
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
setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
[root@localhost grep]# 

？：問號前面的字符重複的次數是0或者1。

[root@localhost grep]# egrep 'o?t' passwd
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
ods:x:999:998:softhsm private keys owner:/var/lib/softhsm:/sbin/nologin
pegasus:x:66:65:tog-pegasus OpenPegasus WBEM/CIM services:/var/lib/Pegasus:/sbin/nologin
systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
polkitd:x:998:996:User for polkitd:/:/sbin/nologin
apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
tomcat:x:91:91:Apache Tomcat:/usr/share/tomcat:/sbin/nologin
abrt:x:173:173::/etc/abrt:/sbin/nologin
saslauth:x:996:76:Saslauthd user:/run/saslauthd:/sbin/nologin
libstoragemgmt:x:995:993:daemon account for libstoragemgmt:/var/run/lsm:/sbin/nologin
unbound:x:388:388:Unbound DNS resolver:/etc/unbound:/sbin/nologin
pkiuser:x:17:17:Certificate System:/usr/share/pki:/sbin/nologin
setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
rtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin
pulse:x:171:171:PulseAudio System Daemon:/var/run/pulse:/sbin/nologin
ntp:x:38:38::/etc/ntp:/sbin/nologin
tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin
pcp:x:383:380:Performance Co-Pilot:/var/lib/pcp:/sbin/nologin
gnome-initial-setup:x:380:377::/run/gnome-initial-setup/:/sbin/nologin
avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
postgres:x:26:26:PostgreSQL Server:/var/lib/pgsql:/bin/bash
dovecot:x:97:97:Dovecot IMAP server:/usr/libexec/dovecot:/sbin/nologin
dovenull:x:379:376:Dovecot's unauthorized user:/usr/libexec/dovecot:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
oprofile:x:16:16:Special user account to be used by OProfile:/var/lib/oprofile:/sbin/nologin
tcpdump:x:72:72::/:/sbin/nologin
tianqi:x:1000:1000:tianqi:/home/tianqi:/bin/bash
[root@localhost grep]# 

|：或者，要使用|,就要使用grep -E或者egrep。

[root@localhost grep]# grep -E 'root|nologin' passwd
root:x:0:0:root:/root:/bin/bash
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
ods:x:999:998:softhsm private keys owner:/var/lib/softhsm:/sbin/nologin
pegasus:x:66:65:tog-pegasus OpenPegasus WBEM/CIM services:/var/lib/Pegasus:/sbin/nologin
systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
polkitd:x:998:996:User for polkitd:/:/sbin/nologin
apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
tomcat:x:91:91:Apache Tomcat:/usr/share/tomcat:/sbin/nologin
colord:x:997:994:User for colord:/var/lib/colord:/sbin/nologin
abrt:x:173:173::/etc/abrt:/sbin/nologin
saslauth:x:996:76:Saslauthd user:/run/saslauthd:/sbin/nologin
libstoragemgmt:x:995:993:daemon account for libstoragemgmt:/var/run/lsm:/sbin/nologin
dirsrv:x:389:389:user for 389-ds-base:/usr/share/dirsrv:/sbin/nologin
rpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin
hsqldb:x:96:96::/var/lib/hsqldb:/sbin/nologin
unbound:x:388:388:Unbound DNS resolver:/etc/unbound:/sbin/nologin
pkiuser:x:17:17:Certificate System:/usr/share/pki:/sbin/nologin
setroubleshoot:x:387:387::/var/lib/setroubleshoot:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
rtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin
pulse:x:171:171:PulseAudio System Daemon:/var/run/pulse:/sbin/nologin
qemu:x:107:107:qemu user:/:/sbin/nologin
ntp:x:38:38::/etc/ntp:/sbin/nologin
radvd:x:75:75:radvd user:/:/sbin/nologin
chrony:x:386:384::/var/lib/chrony:/sbin/nologin
named:x:25:25:Named:/var/named:/sbin/nologin
mysql:x:27:27:MariaDB Server:/var/lib/mysql:/sbin/nologin
tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin
usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin
geoclue:x:385:382:User for geoclue:/var/lib/geoclue:/sbin/nologin
sssd:x:384:381:User for sssd:/:/sbin/nologin
gdm:x:42:42::/var/lib/gdm:/sbin/nologin
rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin
nfsnobody:x:65534:65534:Anonymous NFS User:/var/lib/nfs:/sbin/nologin
pcp:x:383:380:Performance Co-Pilot:/var/lib/pcp:/sbin/nologin
kdcproxy:x:382:379:IPA KDC Proxy User:/:/sbin/nologin
ipaapi:x:381:378:IPA Framework User:/:/sbin/nologin
gnome-initial-setup:x:380:377::/run/gnome-initial-setup/:/sbin/nologin
avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
dovecot:x:97:97:Dovecot IMAP server:/usr/libexec/dovecot:/sbin/nologin
dovenull:x:379:376:Dovecot's unauthorized user:/usr/libexec/dovecot:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
oprofile:x:16:16:Special user account to be used by OProfile:/var/lib/oprofile:/sbin/nologin
tcpdump:x:72:72::/:/sbin/nologin
[root@localhost grep]# 

[root@localhost grep]# egrep -i 'root|bus' passwd
root:x:0:0:root:/root:/bin/bash
operator:x:11:0:operator:/root:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
[root@localhost grep]# 

 

友情連接：阿銘Linux