sed编辑器基础

一、 更多的替换选项
①替换标记

root@localhost sed]# cat data4.txt
This is a test of the test script.
This is the second test of the test script.
[root@localhost sed]# sed 's/test/trial/' data4.txt
This is a trial of the test script.
This is the second trial of the test script.

替换格式：   s/pattern/replacement/flags
4种可用的替换标记：
数字：表明新闻本将替换第几处模式匹配的地方；
g，表明新文本将会替换所有匹配的文本；
p，表明原先行的内容要打印出来；
w file，将替换的结果写到文件中。

可以指定sed编辑器用新文本替换第几处模式匹配的地方。

[root@localhost sed]# sed 's/test/trial/2' data4.txt
This is a test of the trial script.
This is the second test of the trial script.

后面第二个test被替换掉了。

用g替换标记，能替换全部

[root@localhost sed]# sed 's/test/trial/g' data4.txt
This is a trial of the trial script.
This is the second trial of the trial script.

p替换标记会只打印修改过的行，和-n选项（禁止输出）一起使用。

[root@localhost sed]# cat data5.txt
This is a test line.
This is a different line.
[root@localhost sed]# sed -n 's/test/trial/p' data5.txt
This is a trial line.

②替换字符
替换（/），可以用其他字符替换字符串分隔符

[root@localhost sed]# sed -n 's!/bin/bash!/bin/csh!p' /etc/passwd
root:x:0:0:root:/root:/bin/csh
tq2440:x:500:500:tq2440:/home/tq2440:/bin/csh
win:x:501:501::/home/win:/bin/csh

二、使用地址
sed有两种形式的行寻址：
①以数字形式表示行区间
②用文本模式来过滤出行
[address] command

1.数字方式的行寻址

[root@localhost sed]# sed '2s/dog/cat/' data1.txt
The quick brown fox jumps over the lazy dog.
The quick brown fox jumps over the lazy cat.
The quick brown fox jumps over the lazy dog.