sed Cheat Sheet
Command Syntax
/abc/p # Print all with "abc"
/abc/!p # Print all without "abc"
/abc/d # Delete all with "abc"
/abc/!d # Delete all without "abc"
/start/,/end/!d # Select a block
s/abc/def/
s/abc\(...\)ghi/\1/ # Back references
# (see below for correct Shell quoting)
/abc/{s/def/ghi)} # Conditional replace
Appending lines
aHallo # Append 'Hallo' after each line
5 aHallo # Append 'Hallo' after line #5
$ aHallo # Append 'Hallo' to end of file
/abc/r<(printf "%s\n" "Hallo") # Append 'Hallo' after pattern 'abc'
Prepending lines
sed -i '1s;^;new line 1\nanother new line 2\n;' <file>
Advanced use of sed
In-place Editing
To edit file use the -i option this safely changes the file contents without any output redirection needed.
sed -i 's/abc/ABC/' myfile.txt
sed -i '/deleteme/d' *
Drop grep
Often grep and sed are used together. In all those cases grep can be dropped. For example
grep "pattern" file | sed "s/abc/def/"
can be written as
sed -n "/pattern/p; s/abc/def/"
Grouping with sed
Always use single quotes!
sed 's/^.*\(pattern\).*/\1/'
Single Quoting Single Quotes
If you want to do extraction and need a pattern based on single quotes use \x27 instead of trying to insert a single quote. For example:
sed 's/.*var=\x27\([^\x27]*\)\x27.*/\1/'
to extract “some string” from “var=’some string’”. Or if you don’t know about the quoting, but know there are quotes
sed 's/.*var=.\([^"\x27]*\)..*/\1/'
Conditional Replace with sed
sed '/conditional pattern/{s/pattern/replacement/g}'
Prefix files with a boilerplate using sed
sed -i '1s/^/# DO NOT TOUCH THIS FILE!\n\n/' *
Replacing Newlines with sed
The only way to replace newline characters is this:
sed ':a;N;$!ba;s/\n//g' file
Check out this explanation if you want to know why. With GNU sed you might also want to try the -z option:
sed -z "s/\n//g"
Note that the -z option line splits on \0, so this relies on the input text file not containing any \0 which usually should be sufficient.
Selecting Blocks
sed '/first line/,/last line/!d' file
Capitalize word
sed -e "s/\b\(.\)/\u\1/g"