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sed, awk and Regular Expressions Pocket Reference by Arnold Robbins

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1.4. The sed Editor

This section 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

1.4.1. Conceptual Overview

sed is a non-interactive, or stream-oriented, editor. It interprets a script and performs the actions in the script. sed is stream-oriented because, like 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 or pipe, but it can also be directed from the keyboard. Output goes to the screen by default but can be captured in a file or sent through a pipe instead.

The Free Software Foundation has a version of sed, available from ftp://gnudist.gnu.org/gnu/sed/sed-3.02.tar.gz. The somewhat older version, 2.05, is also available.

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," an internal buffer where editing operations are performed.

  • 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 and address tests will be applied to the current line in the pattern space, not the original input line.

  • The original ...

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