sed命令

1  sed命令 帮助

Usage: sed [OPTION]... {script-only-if-no-other-script} [input-file]...

  -n, --quiet, --silent    ###安静模式，只显示被sed处理过的行         
                 suppress automatic printing of pattern space
  -e script, --expression=script ###默认选项，不用写，在命令行操作
                 add the script to the commands to be executed
  -f script-file, --file=script-file  ### 将sed操作写在一个文件里
                 add the contents of script-file to the commands to be executed
  --follow-symlinks
                 follow symlinks when processing in place; hard links
                 will still be broken.
  -i[SUFFIX], --in-place[=SUFFIX]   ### 插入当前行的上一行
                 edit files in place (makes backup if extension supplied).
                 The default operation mode is to break symbolic and hard links.
                 This can be changed with --follow-symlinks and --copy.
  -c, --copy
                 use copy instead of rename when shuffling files in -i mode.
                 While this will avoid breaking links (symbolic or hard), the
                 resulting editing operation is not atomic.  This is rarely
                 the desired mode; --follow-symlinks is usually enough, and
                 it is both faster and more secure.
  -l N, --line-length=N
                 specify the desired line-wrap length for the `l' command
  --posix
                 disable all GNU extensions.
  -r, --regexp-extended   ###支持扩展正则表达式
                 use extended regular expressions in the script.
  -s, --separate ###表示搜索
                 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

例子：

   1）删除2,5行

    

# cat -n  /etc/passwd |sed '2,5d'
     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
     9    mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
    10    uucp:x:10:14:uucp:/var/spool/uucp:/sbin/nologin

2） 添加 在第2行后添加 hello world

# cat -n /etc/passwd|sed '2a hello world' 
     1    root:x:0:0:root:/root:/bin/bash
     2    bin:x:1:1:bin:/bin:/sbin/nologin
hello world

3）添加2行，在第1行后面添加两行 （以续航符号 \, 按Enter键继续输入，以'结束）

]# cat -n /etc/passwd|sed '1a this is frist line 
> this is second line  '
     1    root:x:0:0:root:/root:/bin/bash
this is frist line 
this is second line  

4) 替换，以2,5行替换成 “我 是 谁”

# cat -n /etc/passwd |sed '2,5c 我是谁！ '
     1    root:x:0:0:root:/root:/bin/bash
我是谁！ 
     6    sync:x:5:0:sync:/sbin:/bin/sync

5）显示特定行，只显示5-7行，注意n和p同时使用

# cat -n /etc/passwd |sed -n '5,7p'
     5    lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
     6    sync:x:5:0:sync:/sbin:/bin/sync
     7    shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown

6）显示出ifconfig中的ip地址

# ifconfig eth0 | grep 'inet addr' |sed 's/^.*addr://g' |sed 's/Bcast.*$//g'
192.168.0.35 

# ifconfig eth0 | grep 'inet addr' |awk -F[:] '{print $2}'  | awk '{print $1}'
192.168.0.35

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2. sed的基础用法

  1）删除行首空格

      

# sed 's/^[ ]* //g' test.txt 
zero line
first line

# sed 's/^ * //g' test.txt
zero line
first line

# sed 's/^[[:space:]]* //g' test.txt

2）在第一行插入文本

# sed -i '1 i00000' test.txt

3）在最后一行插入

# sed -i '$ iendendend0000000' test.txt 

4）在匹配行前插入

# sed -i '/zero/ i the 3 line' test.txt

5）在匹配行后插入

sed -i '/the end/ a "this is the end line"' test.txt 

6) 删除空行及行首空格和#号的行

# grep -v  ^# test.txt | sed /^[[:space:]]*$/d | sed '/^$/d'