Useful sed scripts

print one line

sed -n '10p' myfile.txt

do replacement on all lines except line 5

sed '5!/s/foo/bar/' file.txt

do replacement on lines matching regex (eg: lines starting with 'hello')

sed '/^hello/ s/h/H/' file.txt

do replacement from line 5 to end of file

s '1,$ s/foo/bar/' file.txt

Print lines between two regexes

sed -nr '/^foo/,/^bar/p' file.txt

Use custom delimiters to make it easy for some strings that contain slashes

sed 's_/bin/bash_/bin/sh_' file.txt

Insert a space between lowercase/Uppercase characters using & (which represents the regex match)

sed 's/[a-zA-Z]/& /g' file.txt

keep the first word of every line

sed -r s_[a-z]+.*_\1_' file.txt

switch the first two words

sed -r 's_([a-zA-Z]*) ([a-zA-Z]*)_\2 \1_' f1

remove duplicate words (but not triplicate)

sed -r 's_([a-z]+) \1_\1_ig' f1

search and replace for pattern, write just the lines with the replacements in a new file

sed -r 's_foo_bar_w replaced.txt' file.txt

multiple replacements

sed -e 's_foo_bar_' -e 's_hello_HELLO_' file.txt

multiple replacements by using a bash script

#!/bin/bash
sed '
s/a/A/
s/foo/BAR/
s/hello/HELLO/
' <$1

• call with ./myscript.sh myfile.txt

remove comments between lines starting with these two keywords

sed -r '/start/,/end/ s/#.*//' file.txt

view lines minus lines between line starting with pattern and end of file

sed -r '/start/,$ d' file.txt

view lines except lines between line starting with pattern and line ending with pattern

sed -rn '/start/,/end/ !p' file.txt

print until you encounter pattern then quit

sed -r '/start/q' file.txt

insert contents of file after a certain line

sed -r '5 r newfile.txt' file.txt

Append text after lines containing regex (AFTER FOO)

sed '/foo/ a AFTER FOO' file.txt

Insert text after lines containing regex (BEFORE FOO)

sed '/foo/ i BEFORE FOO' file.txt

change line containing regex match

sed '/foo/c FOO IS CHANGED' file.txt

Nested sed ranges with inversion. Between lines 1,100 apply actions where the pattern DOESN'T match.

#!/bin/bash
sed  '
1,100 {
	/foo/ !{
		s_hello_HELLO_
		s_yes_YES
	}
}'

• call with ./script.sh <file.txt

Use nested addresses with change, insert and append to modify: the line before match, the line with match, the line after match.

#!/bin/bash
sed '
/^#/ {
i\
#BEFFORE ORIGINAL COMMENt
a\
#AFTER ORIGINAL COMMENT
c\
# ORIGINAL COMMENT IS NOW THIS LINE
}'

Insert new line before the first comment, after the first comment put in the contents of file and quit immediately afterwards

#!/bin/bash
sed '
/^#/ {
i #BEFORE COMMENT
r myotherfile.txt
q
}'

Transform text

sed 'y/abc/ABC/' file.txt

Copy all the comments (starting with #) to a new file

sed -r '/^#/w comments.txt' file.txt

Print every second line (substitute ~3 for third line, etc)

sed '1~2p' file.txt

Edit file in place but also create a backup

sed -i.bak 's/hello/HELLO/' file.txt