Command-Line Options

Perl expects any command-line options, also known as switches or flags , to come first on the command line. The next item is usually the name of the script, followed by any additional arguments (often filenames) to be passed into the script. Some of these additional arguments may be switches, but if so, they must be processed by the script, since Perl gives up parsing switches as soon as it sees either a non-switch item or the special -- switch that terminates switch processing.

A single-character switch with no argument may be combined (bundled) with the switch that follows it, if any. For example:

#!/usr/bin/perl -spi.bak

is the same as:

#!/usr/bin/perl -s -p -i.bak

Perl recognizes the switches listed in Table 3-1.

Table 3-1. Perl switches

Switch

Function

   

--

Terminates switch processing, even if the next argument starts with a minus. It has no other effect.

   

-0[octnum]

Specifies the record separator ($/) as an octal number. If octnum is not present, the null character is the separator. Other switches may precede or follow the octal number.

   

-a

Turns on autosplit mode when used with -n or -p. An implicit split of the @F array is inserted as the first command inside the implicit while loop produced by -n or -p. The default field delimiter is whitespace; a different field delimiter may be specified using -F.

   

-c

Causes Perl to check the syntax of the script and exit without executing it. More or less equivalent to having exit(0) as the first statement in ...

Get Perl in a Nutshell, 2nd Edition now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.