sed 之正则表达式

[root@freepp ~]# sed
Usage: sed [OPTION]... {script-only-if-no-other-script} [input-file]...

  -n, --quiet, --silent
                 suppress automatic printing of pattern space
  -e script, --expression=script
                 add the script to the commands to be executed
  -f script-file, --file=script-file
                 add the contents of script-file to the commands to be executed
  -i[SUFFIX], --in-place[=SUFFIX]
                 edit files in place (makes backup if extension supplied)
  -c, --copy
                 use copy instead of rename when shuffling files in -i mode
                 (avoids change of input file ownership)
  -l N, --line-length=N
                 specify the desired line-wrap length for the `l' command
  --posix
                 disable all GNU extensions.
  -r, --regexp-extended
                 use extended regular expressions in the script.
  -s, --separate
                 consider files as separate rather than as a single continuous
                 long stream.
  -u, --unbuffered
                 load minimal amounts of data from the input files and flush
                 the output buffers more often
      --help     display this help and exit
      --version  output version information and exit

If no -e, --expression, -f, or --file option is given, then the first
non-option argument is taken as the sed script to interpret.  All
remaining arguments are names of input files; if no input files are
specified, then the standard input is read.

E-mail bug reports to: bonzini@gnu.org .
Be sure to include the word ``sed'' somewhere in the ``Subject:'' field.
[root@freepp ~]#

利用grep和sed提取IP地址：

[root@freepp ~]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:1A:92:37:C0:EB 
          inet addr:192.168.4.7  Bcast:192.168.4.255  Mask:255.255.255.0
          inet6 addr: fe80::21a:92ff:fe37:c0eb/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:595747 errors:0 dropped:0 overruns:0 frame:0
          TX packets:548636 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:106966875 (102.0 MiB)  TX bytes:470101083 (448.3 MiB)
          Interrupt:201

lo        Link encap:Local Loopback 
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:72 errors:0 dropped:0 overruns:0 frame:0
          TX packets:72 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:3760 (3.6 KiB)  TX bytes:3760 (3.6 KiB)

[root@freepp ~]#

ifconfig eth0 | grep 'inet addr'  是什么结果呢？

[root@freepp ~]# ifconfig eth0 | grep 'inet addr'
          inet addr:192.168.4.7  Bcast:192.168.4.255  Mask:255.255.255.0
[root@freepp ~]#

啊哈，明显已经提取到所需的那一行

需要再处理

ifconfig eth0 | grep 'inet addr' | sed 's/^.*addr://g'

[root@freepp ~]# ifconfig eth0 | grep 'inet addr' | sed 's/^.*addr://g'
192.168.4.7  Bcast:192.168.4.255  Mask:255.255.255.0
[root@freepp ~]#

怎么样，看出变了吧，现在类似的要去掉IP后的内容即可

ifconfig eth0 | grep 'inet addr' | sed 's/^.*addr://g' | sed 's/Bcast.*$//g' 

[root@freepp ~]# ifconfig eth0 | grep 'inet addr' | sed 's/^.*addr://g' | sed 's/Bcast.*$//g' 
192.168.4.7 
[root@freepp ~]#

是不是已经达到要求了。

 

ok，这里使用的是eth0 接口，那如果针对行呢？？

使用n参数即可

[root@freepp ~]# ifconfig |sed -n '1,10'p| grep "inet addr"|sed s/^.*addr://g|sed s/.Bca.*$//g
192.168.4.7
[root@freepp ~]#

总结，利用grep提取ip地址的方法：ifconfig |sed -n '1,10'p| grep "inet addr"|sed s/^.*addr://g|sed s/.Bca.*$//g