Sed basic and practice

定义：Sed 是针对数据流的非交谈式编辑器，它在命令行下输入编辑命令并指定文件，然后可以在屏幕上看到编辑命令的输出结果。

好处：Sed 在缓冲区内默认逐行处理数据，所以源文件不会被更改和破坏。

格式：Sed ‘command' filename

原理：Sed 用数字或规则表达式在定位编辑的地址，然后Command告诉Sed如何处理该行。可以打印，删除，或者更改。

#/bin/bash
echo 'here is a sed script'
echo '======= print the content of employees'
cat employees
echo '======= delete line1 to 3 and print'
sed '1,3d' employees
#delete line include frank
sed '/frank/d' employees
#delete line unclude frank
sed '/frank/!d' employees
#print frank line and all line
sed '/frank/p' employees
#print frank line only
sed -n '/frank/p' employees
#delete line4 to end and print
sed '4,$d' employees
#delete last ine and print
sed '$d' employees
#delete line including john and print
sed '/john/d' employees
#replace all john to hello
sed 's/john/hello/g' employees
#replace all john to hello and print replaced only
sed -n 's/john/hello/gp' employees
#print replaced line only
sed -n 's/^john/hello/p' employees
#replace nn to nn. and print
sed 's/[0-9][0-9]$/&.5/' employees
#print replaced line only
sed -n 's/[0-9][0-9]$/&.5/p' employees
#print from eric to mark
sed -n '/eric/,/mark/p' employees
#print line1 to mark
sed -n '1,/^mark/p' employees
#delete line and replace
sed -e '1,3d' -e 's/frank/huma/' employees