sed Editor

Contents:

Conceptual Overview
Command-Line Syntax
Syntax of sed Commands
Group Summary of sed Commands
Alphabetical Summary of sed Commands

This chapter presents the following topics:

• Conceptual overview of sed
• Command-line syntax
• Syntax of sed commands
• Group summary of sed commands
• Alphabetical summary of sed commands

For more information, see the Anonymous tutorial sed & awk, 2d ed., by Dale Dougherty and Arnold Robbins.

Conceptual Overview

sed is a noninteractive, or stream-oriented, editor. It interprets a script and performs the actions in the script. sed is stream-oriented, because, as with many Unix programs, input flows through the program and is directed to standard output. For example, sort is stream-oriented; vi is not. sed's input typically comes from a file but can be directed from the keyboard. Output goes to the screen by default but can be captured in a file instead.

Typical uses of sed include:

• Editing one or more files automatically
• Simplifying repetitive edits to multiple files
• Writing conversion programs

sed operates as follows:

• Each line of input is copied into a pattern space.
• All editing commands in a sed script are applied in order to each line of input.
• Editing commands are applied to all lines (globally) unless line addressing restricts the lines affected.
• If a command changes the input, subsequent commands are applied to the changed line, not to the original input line.
• The original input file is unchanged, because the editing commands modify a copy of the original input line. The copy is sent to standard output (but can be redirected to a file).