Double space
$ sed G
Delete all blank lines and double space
$ sed '/^$/d;G'
Triple space a file
$ sed 'G;G'
Undo double-spacing
$ sed 'n;d'
Insert a blank line above line which matches "regex"
$ sed '/regex/{x;p;x;}'
Insert a blank line below line which matches "regex"
$ sed '/regex/G'
Insert a blank line around line which matches "regex"
$ sed '/regex/{x;p;x;G;}'
Delete line 5-7 in file
$ sed '5,7d' file.txt
Delete every 2nd line starting with line 3
$ sed '3~2d' file.txt
Delete the last line in file
$ sed '$d' file.txt
Delete lines starting with "Hello"
$ sed '/^Hello/d' file.txt
Delete all empty lines
$ sed '/^$/d' file.txt
Delete lines starting with "#"
$ sed '/^#/d' file.txt
Insert text before line 5
$ sed '5i line number five' file.txt
Insert "Example: " before each line that contains "hello"
$ sed '/hello/i Example: ' file.txt
Number line of a file (simple left alignment)
$ sed = file.txt | sed 'N;s/\n/\t/'
Number line of a file (number on left, right-aligned)
$ sed = file.txt | sed 'N; s/^/ /; s/ \*\(.\{6,\}\)\n/\1 /'
Number line of file, but only print numbers if line is not blank
$ sed '/./=' file.txt | sed '/./N; s/\n/ /'
Count lines (emulates "wc -l")
$ sed -n '$='
Append line after line 2
$ sed '2a Text after line 2' file.txt
Append line at the end of the file
$ sed '$a THE END!' file.txt
Append line after every 3rd line starting from line 3
$ sed '3~3a Some text' file.txt
Search for a string and only print the lines that were matched
$ sed -n '/hello/p' file.txt
Case insensitive search
$ sed -n '/hello/Ip' file.txt
Search for a string but only output lines that do not match
$ sed -n '/hello/!p' file.txt
Replace all occurrences of a string
$ sed 's/old/new/g' file.txt
Replace only the nth occurrence of a string
$ sed 's/old/new/2' file.txt
Replace replace a string only on the 5th line
$ sed '5 s/old/new/' file.txt
Replace "world" with "universe" but only if the line begins with "hello"
$ sed '/hello/s/world/universe/' file.txt
Remove "" from the end of each line
$ sed 's/\\$//' file.txt
Remove all whitespace from beginning of each line
$ sed 's/^\s\*//' file.txt
Remove comments. Even those that are at the end of a line
$ sed 's/#.\*$//' file.txt