How do I replace text in a file using sed?

To replace all occurrences of a string in a file, use 'sed 's/old_text/new_text/g' filename'. For example: sed 's/apple/orange/g' fruits.txt will replace all 'apple' with 'orange' in fruits.txt.

Can sed edit files in place?

Yes, use the -i option to edit files in place. For example: sed -i 's/old/new/g' file.txt will modify file.txt directly. You can also create a backup before editing with 'sed -i.bak 's/old/new/g' file.txt'.

sed Command

Q: What does the sed command do in Linux?

The sed (stream editor) command is a powerful text processing tool that can perform basic text transformations on an input stream (a file or input from a pipeline). It is commonly used for finding and replacing text, deleting lines, inserting content, and more.

The sed (stream editor) command is a powerful text processing tool that can perform basic text transformations on an input stream (a file or input from a pipeline). It is commonly used for finding and replacing text, deleting lines, inserting content, and more.

Syntax

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

Description

sed is a non-interactive stream editor. It receives text input, performs operations (like searching, finding, replacing, inserting, deleting) based on a script, and then outputs the transformed text. It does not modify the original file unless explicitly told to do so with the -i option.

Common uses include:

Find and replace text using regular expressions
Delete specific lines or ranges of lines
Insert or append content to lines
Transform text streams from pipelines

Common Options

Option	Description
`-n`, `--quiet`, `--silent`	Suppress automatic printing of pattern space
`-e` script, `--expression=script`	Add the script to the commands to be executed
`-f` script-file, `--file=script-file`	Add the contents of script-file to the commands to be executed
`-i[SUFFIX]`, `--in-place[=SUFFIX]`	Edit files in place (makes backup if SUFFIX supplied)
`-r`, `--regexp-extended`	Use extended regular expressions in the script
`-s`, `--separate`	Consider files as separate rather than as a single continuous stream

Examples

Replace all occurrences of a string

sed 's/old_text/new_text/g' filename.txt

Replaces all occurrences of 'old_text' with 'new_text' in filename.txt and prints to standard output.

Replace in place (with backup)

sed -i.bak 's/old_text/new_text/g' filename.txt

Replaces all occurrences of 'old_text' with 'new_text' directly in filename.txt, creating a backup file named filename.txt.bak.

Delete lines containing a pattern

sed '/pattern/d' filename.txt

Deletes all lines containing 'pattern' from filename.txt and prints the result.

Print specific lines by number

sed -n '5p' filename.txt

Prints only the 5th line of filename.txt.

Insert a line before a pattern

sed '/pattern/i\New line to insert' filename.txt

Inserts 'New line to insert' before each line containing 'pattern'.

Append a line after a pattern

sed '/pattern/a\New line to append' filename.txt

Appends 'New line to append' after each line containing 'pattern'.