Awk

External

• http://en.wikipedia.org/wiki/Awk
• Awk by Example
  • http://www.ibm.com/developerworks/linux/library/l-awk1.html
  • http://www.ibm.com/developerworks/linux/library/l-awk2.html
  • http://www.ibm.com/developerworks/linux/library/l-awk3.html

Internal

• Linux
• sed

Overview

awk handles a stream of text as a sequence of records. The default record separator is the new line, so by default each line is handled as a record. Each record is broken up into a sequence of fields. By default, the field separator is white space. An awk program consists in condition-action statements, that are applied to the records, as they are fed into awk. Each record is scanned for the condition, which can be a pattern, among other things, and for each condition that matches, the associated action is executed.

awk '<program>' <file-to-process>

The program is a succession of:

condition { action }

Example:

awk '{print $1}' ./sample.txt

For the above, the condition matches all records and the action prints out the first field.

The program can be specified in a separate text file, which is provided to awk by preceding the program file name with -f:

awk -f <program-file-name> <file-to-process>

Referring Fields

The fields are referred to with $<field-number> where field-number is 1-based: the first field in the record is $1.

Comments

Everything that follows a '#' is a comment. The '#' does not have to be on the first position in line.