sed: Stream Editor for Text Manipulation

sed (Stream Editor) is a powerful command-line tool used for manipulating text streams. It’s like a search-and-replace tool on steroids, allowing you to modify text files in various ways.

sed is a valuable tool for automating text transformations. With some practice, you’ll find it indispensable for tasks like:

• Fixing typos in multiple files.
• Modifying configuration files.
• Extracting specific information from text.

sed Key Concepts 🔗

• Streams: sed works on streams of text data, which can be from files, standard input, or other sources.
• Patterns: You use patterns (often regular expressions) to match specific parts of the text.
• Commands: sed executes commands (like substitution, deletion, insertion) on the matched text.

Common Usages of sed 🔗

Substitution 🔗

Replace all occurrences of “oldword” with “newword”:

sed 's/oldword/newword/g' input.txt

• s: The substitution command.
• g: Replace all occurrences on each line.

Deletion 🔗

Delete all lines containing the word “keyword”:

sed '/keyword/d' input.txt

• d: The delete command.

Insertion 🔗

Insert a line before lines matching the pattern:

sed '/pattern/i\
This line is inserted before the pattern.' input.txt

• i: The insert command.

Printing Lines 🔗

Print lines that match the pattern:

sed -n '/pattern/p' input.txt

• -n: Suppress normal output.
• p: Print lines that match the pattern.

More Examples 🔗

Replace all apple (basic regex) occurrences with mango (basic regex) in all input lines and print the result to stdout:

command | sed 's/apple/mango/g'

Execute a specific script (f)ile and print the result to stdout:

command | sed -f path/to/script_file.sed

Replace all apple (extended regex) occurrences with APPLE (extended regex) in all input lines and print the result to stdout:

command | sed -E 's/(apple)/\U\1/g'

Print just a first line to stdout:

command | sed -n '1p'

Replace all apple (basic regex) occurrences with mango (basic regex) in a file and save a backup of the original to file.bak:

sed -i bak 's/apple/mango/g' path/to/file

Notes of beginners 🔗

• Start with simple commands and gradually increase complexity.
• Use single quotes (') to enclose sed commands.
• Refer to the sed manual for a comprehensive list of commands and options. See the manual using the command man sed, or check the online version on Github .

See also: awk , ed .

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