Linux Command Line and Shell Scripting Bible, 4th Edition

APPENDIX BQuick Guide to sed and gawk

IN THIS APPENDIX

• The basics for using sed
• What you need to know about gawk

If you do any type of data handling in your shell scripts, most likely you'll need to use either the sed program or the gawk program (and sometimes both). This appendix provides a quick reference for sed and gawk commands that come in handy when working with data in your shell scripts.

The sed Editor

The sed editor can manipulate data in a data stream based on commands you either enter into the command line or store in a command text file. It reads one line of data at a time from the input and matches that data with the supplied editor commands, changes data in the stream as specified in the commands, and then outputs the new data to STDOUT.

Starting the sed editor

Here's the format for using the sed command:

sed options script file

The options parameters allow you to customize the behavior of the sed command and include the options shown in Table B.1.

TABLE B.1 The sed Command Options

Option	Description
‐e script	Adds commands specified in script to the commands run while processing the input
‐f file	Adds the commands specified in the file file to the commands run while processing the input
‐n	Doesn't produce output for each command but waits for the print command

The script parameter specifies a single command to apply against the stream data. If more than one command is required, you must use either the ‐e option, to specify them ...