sed小结

sed [options] 'command' file(s)   
sed [options] -f scriptfile file(s)  
 
1.options
-n 取消默认输出，只有经过sed特殊处理行(或者动作)才会被列出来
-e 多重编辑模式
-f 指定sed脚本文件名
 
2. command
1) d  从模板块（Pattern space）位置删除行
 
# delete the 3rd line 
sed '3d' file

# delete lines from the 3rd to end
sed '3,$d' file

# delete line it contains "line"
sed '/line/'d file
 

2) p  打印模板块的行
 
# "abc start\nefg middle" 
echo "abc start\nefg middle\nhij end\nover" | sed -n '/start/,/middle/p'  

# "efg middle\nhig end" 
echo "abc start\nefg middle\nhij end\nover" | sed -n '2,/end/p'   

# "abc start123\nefg middle123"
echo "abc start\nefg middle\nhij end\nover" | sed -n '/start/,/middle/s/$/123/p'   
 
# grep def 
echo "abc\ndef\nghi\njkl" | sed -n '/def/p'
echo "abc\ndef\nghi\njkl" | sed '/def/!d'

# grep -v def
echo "abc\ndef\nghi\njkl" | sed -n '/def/!p'# "abc\nghi\njkl" 
echo "abc\ndef\nghi\njkl" | sed '/def/d'# "abc\nghi\njkl" 

# abc，匹配行的前一行
echo "abc\ndef\nghi\njkl" | sed -n  '/def/{g;1!p;};h'

# ghi，匹配行的后一行
echo "abc\ndef\nghi\njkl" | sed -n  '/def/{n;p}'
 

3) s/re/string/  用string替换正则表达式re
echo "abcdefg" | sed 's/abc/123/g'        # 123defg
echo "abcdefg" | sed -n 's/^abc/123/p'    # 123defg
echo "abcdefg" | sed 's#\(abc\)defg#\1#'  # abc

# delete spaces in front of each row
sed 's/^[ ]*/g' file 
sed 's/^ */g' file    
sed 's/^[[:space:]]*//g file 
 
4) r file 从file中读行  eg: file contains "123\n456"
# abc\n123\n456\ndef
echo "abc\ndef" | sed '/abc/r file'   

 
5) w file  向file中写行，清空原有文件内容
# now, file content is "abc"
echo "abc\ndef" | sed -n '/abc/w file'  
 
6) a\ 当前行后面加入一行文本
# "abc\n123\ndef", '\'换行时，不可少，最后一行，可省略
echo "abc\ndef" | sed '/^abc/a\123'  
 
7) i\ 在当前行前面插入一行文本
# "123\nabc\ndef"
echo "abc\ndef" | sed '/^abc/i\123' 
 

8) h  将 hold space 中的内容使用 pattern space 中的内容来替换(清空暂存缓冲区)
9) H  将 hold space 中的内容使用 加上一个 trailing newline，而后 append pattern space(不清空暂存缓冲区)
 
10) g  将 pattern space 中的内容使用 hold space 中的内容来替换
11) G  将 pattern space 中的内容使用 加上一个 trailing newline，而后 append hold space
 
12) !  表示后面的命令对所有没有被选定的行发生作用

# "abc\ndef\nghi\ndef"
echo "abc\ndef\nghi" | sed -e '/def/h' -e '$G'

# "abc\ndef\nghi\n\ndef"  
echo "abc\ndef\nghi" | sed -e '/def/H' -e '$G'

# "abc\ndef\ndef"  
echo "abc\ndef\nghi" | sed -e '/def/h' -e '$g' 

# "abc\ndef\n\ndef" 
echo "abc\ndef\nghi" | sed -e '/def/H' -e '$g'  

#  "jkl\nghi\ndef\nabc" 
echo "abc\ndef\nghi\njkl" | sed '1!G;h;$!d'    

#  "abc\n\ndef\n" 
echo "abc\ndef" | sed G  

# "abc\n\ndef\n"                       
echo "abc\n\n\ndef" | sed '/^$/d;G'
 
# "abc\n\ndef\nghi\njkl", add a blank line before the matching one 
echo "abc\ndef\nghi\njkl" | sed '/def/{x;p;x;}' 

# "abc\ndef\n\nghi\njkl", add a blank line after the matching one
echo "abc\ndef\nghi\njkl" | sed '/def/G' 

# "abc\n\ndef\n\nghi\njkl", add a blank line before and after the matching one
echo "abc\ndef\nghi\njkl" | sed '/def/{x;p;x;G}' 
 
 
13) n  读取下一个输入行，用下一个命令处理新的行而不是用第一个命令
echo "abc\ndef" | sed '/abc/{n;s/e/E/;}' #  "abc\ndEf"
echo "abc\ndef\nghi\njkl" | sed 'n;d'  #  "abc\nghi", delete the even lines
 
14) y与tr类似，字符替换
#  "ABC\ndef"
echo "abc\ndef" | sed '1y/abcdef/ABCDEF/'  
 
15) =  打印当前行号码
#  2
echo "abc\ndef\nghi\njkl" | sed -n '/def/='   

# 4,  wc -l
echo "abc\ndef\nghi\njkl" | sed -n '$=' 


16) q 退出
# "abc\ndef", head -2
echo "abc\ndef\nghi\njkl" | sed 2q

# jkl, tail -1
echo "abc\ndef\nghi\njkl" | sed -e :a -e '$q;N;2,$D;ba'   

# "ghi\njkl", tail -2
echo "abc\ndef\nghi\njkl" | sed '$!N;$!D'

# jkl, tail -1
echo "abc\ndef\nghi\njkl" | sed '$!d'

# jkl, tail -1
echo "abc\ndef\nghi\njkl" | sed  -n '$p'

3. meta characters
^锚定行的开始 
$锚定行的结束
.匹配一个非换行符的字符
*匹配零或多个字符 如：/*sed/匹配所有模板是一个或多个空格后紧跟sed的行。
[]匹配一个指定范围内的字符
[^]匹配一个不在指定范围内的字符
\(..\)保存匹配的字符
echo "abcdefg" | sed 's/\(abc\)def/\1***/'   # abc***g
 
&保存搜索字符用来替换其他字符
echo "abcdefg" | sed 's/d/--&--/'   # abc--d--efg
 
\<锚定单词的开始
\>锚定单词的结束
x\{m\}字符x重复m次
x\{m,\}字符x重复至少m次
x\{m,n\}字符x重复至少m次，至多n次