14. grep, egrep, fgrep, rgrep - print lines matching a pattern
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14. grep, egrep, fgrep, rgrep - print lines matching a pattern

14.1. 刪除空行

$ cat file | grep '.'

14.2. -v, --invert-match

grep -v "grep"

[root@development ~]# ps ax | grep httpd
 6284 ?        Ss     0:10 /usr/local/httpd-2.2.14/bin/httpd -k start
 8372 ?        S      0:00 perl ./wrapper.pl -chdir -name httpd -class com.caucho.server.resin.Resin restart
19136 ?        S      0:00 /usr/local/httpd-2.2.14/bin/httpd -k start
19749 pts/1    R+     0:00 grep httpd
31530 ?        Sl     0:57 /usr/local/httpd-2.2.14/bin/httpd -k start
31560 ?        Sl     1:12 /usr/local/httpd-2.2.14/bin/httpd -k start
31623 ?        Sl     1:06 /usr/local/httpd-2.2.14/bin/httpd -k start
[root@development ~]# ps ax | grep httpd | grep -v grep
 6284 ?        Ss     0:10 /usr/local/httpd-2.2.14/bin/httpd -k start
 8372 ?        S      0:00 perl ./wrapper.pl -chdir -name httpd -class com.caucho.server.resin.Resin restart
19136 ?        S      0:00 /usr/local/httpd-2.2.14/bin/httpd -k start
31530 ?        Sl     0:57 /usr/local/httpd-2.2.14/bin/httpd -k start
31560 ?        Sl     1:12 /usr/local/httpd-2.2.14/bin/httpd -k start
31623 ?        Sl     1:06 /usr/local/httpd-2.2.14/bin/httpd -k start

14.3. Output control

14.3.1. -o, --only-matching show only the part of a line matching PATTERN
			
$ curl -s http://www.example.com | egrep -o '<a href="(.*)">.*</a>' | sed -e 's/.*href="\([^"]*\)".*/\1/'
			
			
$ mysqlshow | egrep -o "|\w(.*)\w|"
Databases
information_schema
test
14.3.2. 遞歸操作

遞歸查詢

$ sudo grep -r 'neo' /etc/*

遞歸替換

			
for file in $( grep -rl '8800.org' *  | grep -v .svn ); do
    echo item: $file
	[ -f $file ] && sed -e 's/8800\.org/sf\.net/g' -e 's/netkiller/neo/g' $file >$file.bak; cp $file.bak $file;
done
14.3.3. -c, --count print only a count of matching lines per FILE
$ cat /etc/resolv.conf
nameserver localhost
nameserver 208.67.222.222
nameserver 208.67.220.220
nameserver 202.96.128.166
nameserver 202.96.134.133
$ grep -c nameserver /etc/resolv.conf
5
			
# grep -c GET /www/logs/access.log
188460

# grep -c POST /www/logs/access.log
421

14.4. Context control

14.4.1. -A, --after-context=NUM print NUM lines of trailing context

返回匹配當前行至下面N行

# grep -A1 game /etc/passwd
games:x:12:100:games:/usr/games:/sbin/nologin
gopher:x:13:30:gopher:/var/gopher:/sbin/nologin
			
# grep -A2 game /etc/passwd
games:x:12:100:games:/usr/games:/sbin/nologin
gopher:x:13:30:gopher:/var/gopher:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
14.4.2. -B, --before-context=NUM print NUM lines of leading context

返回匹配當前行至上面N行

# grep -B1 game /etc/passwd
operator:x:11:0:operator:/root:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin

# grep -B2 game /etc/passwd
uucp:x:10:14:uucp:/var/spool/uucp:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin
14.4.3. -C, --context=NUM print NUM lines of output context
-NUM same as --context=NUM
neo@neo-OptiPlex-380:~$ grep -C 1 new /etc/passwd
mail:x:8:8:mail:/var/mail:/bin/sh
news:x:9:9:news:/var/spool/news:/bin/sh
uucp:x:10:10:uucp:/var/spool/uucp:/bin/sh

neo@neo-OptiPlex-380:~$ grep -C 5 new /etc/passwd
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/bin/sh
man:x:6:12:man:/var/cache/man:/bin/sh
lp:x:7:7:lp:/var/spool/lpd:/bin/sh
mail:x:8:8:mail:/var/mail:/bin/sh
news:x:9:9:news:/var/spool/news:/bin/sh
uucp:x:10:10:uucp:/var/spool/uucp:/bin/sh
proxy:x:13:13:proxy:/bin:/bin/sh
www-data:x:33:33:www-data:/var/www:/bin/sh
backup:x:34:34:backup:/var/backups:/bin/sh
list:x:38:38:Mailing List Manager:/var/list:/bin/sh

# grep -3 game /etc/passwd
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
uucp:x:10:14:uucp:/var/spool/uucp:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin
gopher:x:13:30:gopher:/var/gopher:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
nobody:x:99:99:Nobody:/:/sbin/nologin
14.4.4. --color
# grep --color root  /etc/passwd
root:x:0:0:root:/root:/bin/bash
operator:x:11:0:operator:/root:/sbin/nologin

可以通過alias別名啟用--color選項

alias egrep='egrep --color=auto'
alias fgrep='fgrep --color=auto'
alias grep='grep --color=auto'

加入.bashrc中，每次用戶登錄將自動生效

			
# enable color support of ls and also add handy aliases
if [ -x /usr/bin/dircolors ]; then
    test -r ~/.dircolors && eval "$(dircolors -b ~/.dircolors)" || eval "$(dircolors -b)"
    alias ls='ls --color=auto'
    #alias dir='dir --color=auto'
    #alias vdir='vdir --color=auto'

    alias grep='grep --color=auto'
    alias fgrep='fgrep --color=auto'
    alias egrep='egrep --color=auto'
fi

14.5. Regexp selection and interpretation

n 開頭

$ grep '^n' /etc/passwd
news:x:9:9:news:/var/spool/news:/bin/sh
nobody:x:65534:65534:nobody:/nonexistent:/bin/sh
neo:x:1000:1000:neo chan,,,:/home/neo:/bin/bash
nagios:x:116:127::/var/run/nagios2:/bin/false

bash 結尾

$ grep 'bash$' /etc/passwd
root:x:0:0:root:/root:/bin/bash
neo:x:1000:1000:neo chan,,,:/home/neo:/bin/bash
postgres:x:114:124:PostgreSQL administrator,,,:/var/lib/postgresql:/bin/bash
cvsroot:x:1001:1001:cvsroot,,,,:/home/cvsroot:/bin/bash
svnroot:x:1002:1002:subversion,,,,:/home/svnroot:/bin/bash

中間包含 root

$ grep '.*root' /etc/passwd
root:x:0:0:root:/root:/bin/bash
cvsroot:x:1001:1001:cvsroot,,,,:/home/cvsroot:/bin/bash
svnroot:x:1002:1002:subversion,,,,:/home/svnroot:/bin/bash
14.5.1. .*
			
$ curl -s http://www.example.com | egrep -o '<a href=(.*)>.*</a>'
14.5.2. 2010:(13|14|15|16)

regular 匹配一組

egrep "2010:(13|14|15|16)"  access.2010-11-18.log > apache.log
			
ps ax |grep -E "mysqld|httpd|resin"
14.5.3. []與{}

源檔案

# cat /etc/fstab 

#
# /etc/fstab
# Created by anaconda on Sat Sep 10 00:25:46 2011
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=091f295e-ea6d-4f57-9314-e2333f7ebff7 /                       ext4    defaults        1 1
UUID=b3661a0b-2c50-4e18-8030-be2d043cbfc4 /www                    ext4    defaults        1 2
UUID=4d3468de-a2ac-451c-b693-3bdca8832096 swap                    swap    defaults        0 0
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0

匹配每行包含4個連續字元的字元串的行。

# grep '[A-Z]\{4\}' /etc/fstab 
UUID=091f295e-ea6d-4f57-9314-e2333f7ebff7 /                       ext4    defaults        1 1
UUID=b3661a0b-2c50-4e18-8030-be2d043cbfc4 /www                    ext4    defaults        1 2
UUID=4d3468de-a2ac-451c-b693-3bdca8832096 swap                    swap    defaults        0 0

14.6. ^M

fgrep -rl `echo -ne '\r'` .

find . -type f -exec grep $'\r' {} +

14.7. egrep

egrep = grep -E 在egrep中不許看使用轉意字元，例如

# grep '\(oo\).*\1' /etc/passwd 
root:x:0:0:root:/root:/bin/bash

# grep -E '(oo).*\1' /etc/passwd
root:x:0:0:root:/root:/bin/bash

# egrep '(oo).*\1' /etc/passwd
root:x:0:0:root:/root:/bin/bash
			
$ snmpwalk -v2c -c public 172.16.1.254 | egrep -i 'if(in|out)'

for pid in $(ps -axf |grep 'php-cgi' | egrep egrep "0:00.(6|7|8|9)"'{print $1}'); do kill -9 $pid; done

for pid in $(ps -axf |grep 'php-cgi' | egrep "0:(0|1|2|3|4|5)0.(6|7|8|9)" |awk '{print $1}'); do kill -9 $pid; done
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