in reply to Detecting if a program or file exists

use strict;
use warnings;

require 5.8.7;

print "Hello World!\n";

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I only have 5.8.4 installed at home, and this prints:

Perl v5.8.7 required--this is only v5.8.4, stopped at math1.pl line 4.

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Modify the code to require 5.8.3, and it prints:

Hello World!

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Replies are listed 'Best First'.
Re^2: Detecting if a program or file exists
by FM (Acolyte) on Oct 18, 2005 at 04:29 UTC
    What about if I want to make sure a module (Win32::DirSize) is installed? And what about another program that only has one executable file?
    Thanks,
    FM
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      What about if I want to make sure a module (Win32::DirSize) is installed? 
      # see perldoc -f require for more info
my $class = 'Win32::DirSize';
eval "require $class" or die "Couldn't load $class: $@";

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      And what about another program that only has one executable file? 
      my $binary = "/path/to/executable";
-x $binary or die "$binary not found";

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[d/l]
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        And what about another program that only has one executable file? 
        my $binary = "/path/to/executable";
-x $binary or die "$binary not found";

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        FM seems to be under Windows, since he asks about Win32::DirSize. But I guess -x is *NIX-centric and I don't know how it would behave under redmondish environments. Maybe it would just evaporate silently to -f, but I would probably use directly the latter: 
        -f or die "`$_' binary not found\n" for 'C:/path/to/executable';

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[d/l]
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        You might be able to determine if a module is installed without explicitly requiring or using it by using a technique I described in Re: Case Insensitivity on Windows.
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        Thanks a bunch.
        It worked as expected, however, the -x did not work and I finally use -e. How is this going to affect what I am trying to do? Thanks, FM
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