Sed - Delete one or more lines from a file

Sed - Delete one or more lines from a file
 

Syntax: 

 

C代码  

sed '{[/]<n>|<string>|<regex>[/]}d' <fileName>         

sed '{[/]<adr1>[,<adr2>][/]d' <fileName>  

 

/.../=delimiters

n = line number

string = string found in in line

regex = regular expression corresponding to the searched pattern

addr = address of a line (number or pattern )

d = delete

 

Examples 

 

Remove the 3rd line:

C代码  

sed '3d' fileName.txt  

 

Remove the line containing the string "awk":

C代码  

sed '/awk/d' filename.txt  

 

Remove the last line:

C代码  

sed '$d' filename.txt  

 

Remove all empty lines:

C代码  

sed '/^$/d' filename.txt         

sed '/./!d' filename.txt  

 

Remove the line matching by a regular expression (by eliminating one containing digital characters, at least 1 digit, located at the end of the line):

C代码  

sed '/[0-9/][0-9]*$/d' filename.txt  

 

Remove the interval between lines 7 and 9:

C代码  

sed '7,9d' filename.txt  

 

The same operation as above but replacing the address with parameters:

C代码  

sed '/-Start/,/-End/d' filename.txt  

 

The above examples are only changed at the display of the file (stdout1= screen). 

 

For permanent changes to the old versions (<4) use a temporary file for GNU sed using the "-i[suffix]":

C代码  

sed -i".bak" '3d' filename.txt  

 

Task: Remove blank lines using sed

Type the following command:

C代码  

$ sed '/^$/d' input.txt > output.txt  

 

Task: Remove blank lines using grep

C代码  

$ grep -v '^$' input.txt > output.txt  

 

Both grep and sed use special pattern ^$ that matchs the blank lines. Grep -v option means print all lines except blank line.

 

Let us say directory /home/me/data/*.txt has all text file. Use following for loop (shell script) to remove all blank lines from all files stored in /home/me/data directory:

C代码  

#!/bin/sh  

files="/home/me/data/*.txt"  

for i in $files  

do  

  sed '/^$/d' $i > $i.out  

  mv  $i.out $i  

done  

 

Updated for accuracy.