sed - Delete one or more lines from a file

USESFRBR

January 2014

Unix utility SED provides an effective and a versatile way of deleting one or more lines from a designated file to match the needs of the user. This Unix command is used for command line processing. This utility can be used to delete expressions from a file which can be identified by a specifying delimiter (like comma, tab, space, etc.), by line number, by searching for a string, expression or the address of a line in the syntax of SED. 

[Sed] Delete one or more lines from a file

Here is how to remove one or more lines from a file. 


Syntax: 

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: 

sed '3d' fileName.txt

Remove the line containing the string "awk": 

sed '/awk/d' filename.txt

Remove the last line: 

sed '$d' filename.txt

Remove all empty lines: 

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): 

sed '/[0-9/][0-9]*$/d' filename.txt

Remove the interval between lines 7 and 9: 

sed '7,9d' filename.txt 

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

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]": 

sed -i".bak" '3d' filename.txt