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

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