Linux in a Nutshell, Fifth Edition

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Chapter 11: The gawk Programming Language

This is the Title of the Book, eMatter Edition

Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.

sub

sub(regex, str [, target])

Substitute str for first match of the regular expression regex in the

string target.Iftarget is not supplied, defaults to $0. Returns 1 if

successful, 0 otherwise. Use & in the replacement string to stand

for the text matched by the pattern.

substr

substr(string, beg [, len])

Return substring of string at beginning position beg (counting from

1), and the characters that follow to maximum specified length len.

If no length is given, use the rest of the string.

system

system(command)

Function that executes the specified command and returns its exit

status. The status of the executed command typically indicates

success or failure. A value of 0 means that the command executed

successfully. A nonzero value indicates a failure of some sort. The

documentation for the command you’re running will give you the

details.

awk does not make the output of the command available for

processing within the awk script. Use command | getline to read

the output of a command into the script.

systime

systime( ) {G}

Return a time-of-day value in seconds since midnight, January 1,

1970, UTC.

Example

Log the start and end times of a data-processing program:

BEGIN {

now = systime( )

mesg = strftime("Started at %m/%d/%Y %H:%M:%S",

now)

print mesg ...