sed

The sed (stream editor) command is used to perform basic text transformations on an input stream (a file or input from a pipeline). It is most commonly used for finding and replacing text using regular expressions.

Basic Syntax

sed [OPTION]... {script-only-if-no-other-script} [input-file]...

Common Options

Option	Description
-e script	Add the script to the commands to be executed.
-i[SUFFIX]	Edit files in place (makes backup if SUFFIX supplied).
-n, --quiet, --silent	Suppress automatic printing of pattern space.
-E, -r	Use extended regular expressions in the script.

Real-world Examples

1. Basic find and replace (first occurrence per line):

   sed 's/apple/orange/' fruits.txt

2. Global find and replace (all occurrences):

   sed 's/apple/orange/g' fruits.txt

3. In-place find and replace (modifies the file directly):

   sed -i 's/foo/bar/g' config.txt

4. Delete lines matching a pattern:

   sed '/delete_me/d' file.txt