sed有以下几种常用的工作模式：
-n，静态处理命令，不涉及的行不打印；
-e，默认选项，把sed后的输入当做命令来执行；
-i，会直接修改文件；
-r，扩展正则表达式。
直接讲述实例：
cat sedExample.txt#输出文件查看一下内容，第一行是空行
today is May
today date is 24th May
today is Wednesday
what day is it today
what a beautiful
it is the last day of the word
打印指定的行（含有May字符的行）
cat sedExample.txt |sed -n '/May/p'
today is May
today date is 24th May
打印指定的行，加上-e，结果也一样，所以一般情况下可以省略-e
cat sedExample.txt |sed -ne '/May/p'
today is May
today date is 24th May
删除指定的行（含有May字符的行）
cat sedExample.txt |sed '/May/d'
today is Wednesday
what day is it today
what a beautiful
it is the last day of the word
删除以what开头的行
cat sedExample.txt |sed '/^what/d'
today is May
today date is 24th May
today is Wednesday
it is the last day of the word
先删除空行，再删除以May结尾的行，这个时候-e是不能省略的
cat sedExample.txt |sed -e '/^$/d' -e '/May/d'
today is Wednesday
what day is it today
what a beautiful
it is the last day of the word
或者，对命令加上{}
cat sedExample.txt |sed '{/^$/d; /May/d}'
today is Wednesday
what day is it today
what a beautiful
it is the last day of the word
在today前添加this
cat sedExample.txt |sed 's/today/this &/'
this today is May
this today date is 24th May
this today is Wednesday
what day is it this today
what a beautiful
it is the last day of the word
在May后添加 Liunx
cat sedExample.txt |sed 's/May/& Linux/'
today is May Linux
today date is 24th May Linux
today is Wednesday
what day is it today
what a beautiful
it is the last day of the word
在有what行的行首，加上#
cat sedExample.txt |sed '/what/s/^/#/'
today is May
today date is 24th May
today is Wednesday
#what day is it today
#what a beautiful
it is the last day of the word
在有day单词行的行尾部，加上#
cat sedExample.txt |sed '/\<day\>/s/$/#/'
today is May
today date is 24th May
today is Wednesday
what day is it today#
what a beautiful
it is the last day of the word#
注意，以上的操作均未改动原文件
cat sedExample.txt
today is May
today date is 24th May
today is Wednesday
what day is it today
what a beautiful
it is the last day of the word
如果要改动原文件需要加上-i
此外sed还有一个比较6的功能，就是批量更改文件名
列出文件下的.txt文件
ls *.txt
dna.txt geoMatrix.txt geox.txt gg.txt sedExample.txt x.txt
将geo...txt文件，改成GEO...txt
ls *.txt|sed -n 's/\(geo\(.*\)\)/mv \1 GEO\2/p'
mv geoMatrix.txt GEOMatrix.txt
mv geox.txt GEOx.txt
ls *.txt|sed -n 's/\(geo\(.*\)\)/mv \1 GEO\2/p'|bash
ls *.txt
dna.txt GEOMatrix.txt GEOx.txt gg.txt sedExample.txt x.txt
