Testing perlfuncs (getopt) for true/false. (yeah i'm newbie.)

[John W. Krahn]

ThePotPlants wrote:

>
> I keep seeing in the documentation about functions returning 1 or 0 true or
> false... But I can't see how to test for it.
> I want to know how to "test" something to see if it is true or false. Both
> in general, and specifically for my problem.

if ( $scalar ) {
print "$scalar is true\n"
}
else {
print "$scalar is false\n"
}


unless ( $scalar ) {
print "$scalar is false\n"
}
else {
print "$scalar is true\n"
}

> My particular problem is using Getopt::Std;
> My code works.. (sort of), but I know i'm not using it properly.
>
> Getopt takes command line options and the following values (which is pretty
> cool.)
>
> Essentially I'm testing to see if the associated value is null to decide
> whether to call the sub routines, rather than testing if the option has been
> invoked.
>
> See my programme below.
>
> If no options are supplied the else condition should complain "invalid
> option".
>
> In my programme -e is the first valid option and -h is for help.
> If I type: "opt2.pl -e arg1" then the argument arg1 is passed so that
> variable $opt_e = arg1. And it calls the sub. (hoorah!)
> If I type "opt2.pl -e " i.e with no argument then it fails, and complains
> "invalid option". (also hoorah.. of sorts..)
>
> It's all good so far... now the annoying bit...
>
> If want help I should just type: "opt2.pl -h"
>
> But because I have not typed something after the -h then the value $opt_h is
> empty. Even though the option is activated.
>
> Specifically: How do I test $opt_h to see if is true or false? or rather to
> see if -h has been invoked?
> Generally: How can you test a variable to see if it's "not null" / if
> there's something there/ id it's true/false/1/0 etc etc...

perldoc -f defined

> Any help (which doesn't include RTFM) would be greatly appreciated

Oops, too late. :-)

> #!/usr/bin/perl

use warnings;
use strict;

> use Getopt::Std;
>
> getopt('eh');

You might want to use getopts() instead of getopt(), it has better
features. Also the two argument form of getopt() or getopts() will work
better when warnings and strict are enabled.

my %opt;
getopts( 'e:h', \%opt );

> print "
> P1 Option -e $opt_e
> P2 Option -h $opt_h
> \n" ;
>
> if ($opt_h ne "" ) {&hlp();
> }
> elsif ($opt_e ne "" ) {&proc1($opt_e) ;
> }
> else {print "invalid option \n" ;
> }

if ( exists $opt{ h } ) { hlp() }
elsif ( exists $opt{ e } ) { proc1( $opt{ e } ) }

> sub hlp{ print "
> Usage opt2.pl -[eh]
> -e environment
> -h help \n" ;
> return 1;
> }
>
> sub proc1 { print "yeah it works \n" ; return 1 ;}

John
--
use Perl;
program
fulfillment

[Tad McClellan]

ThePotPlants <thepotplants@yahoo.com> wrote:

> Any help (which doesn't include RTFM) would be greatly appreciated

So long then.


--
Tad McClellan SGML consulting
[email]tadmc@augustmail.com[/email] Perl programming
Fort Worth, Texas

[Uri Guttman]

no attachments. just paste in the code or a url to it.

uri

--
Uri Guttman ------ [email]uri@stemsystems.com[/email] -------- [url]http://www.stemsystems.com[/url]
--Perl Consulting, Stem Development, Systems Architecture, Design and Coding-
Search or Offer Perl Jobs ---------------------------- [url]http://jobs.perl.org[/url]

[ThePotPlants]

"Uri Guttman" <uri@stemsystems.com> wrote in message
news:x74r279lys.fsf@mail.sysarch.com...

> no attachments. just paste in the code or a url to it.

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