in reply to How to detect X?

How about a plain old eval? 
#!/usr/bin/perl
use warnings;
use strict;
use Tk;

my $mw;
my $xtest =  eval( 'my $mw = new MainWindow;' );

if($@) {
 chomp($@);
 print "X error: '$@'\n";
  } else {
   print "X ok\n";
   }

MainLoop;

[download]
I'm not really a human, but I play one on earth. flash japh

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Re^2: How to detect X?
by blazar (Canon) on Feb 21, 2005 at 12:55 UTC
    How about a plain old eval?
    Indeed: 432984!
[reply]
       eval really isn't reliable here. The program may very well start in X if X is running, even if it is not called under X.
       IMHO, you really should check for $ENV{DISPLAY}, if X is running and DISPLAY is not set it is really the user's problem, not yours.
       Some gui toolkits have their own internal checks for this stuff, gtk has something like init_check() (wondering if it can run or not) maybe you could find something similar in Tk. This seems too low-level though for whatever the gui toolkit not to have.
       But again, until then, use $ENV{DISPLAY}. If the user doesn't have it set and has X running, i can bet it wouldn't be just your application he would have problems with.

      --
      perl -MLWP::Simple -e'print$_%%\n|,<br> get(q=http://cpan.org/misc/japh=)))'

[reply]
        $ENV{DISPLAY} not being set if X is running is only one part of the problem - and the less problematic one, because in that case, it runs the command line version. The other problem is $ENV{DISPLAY} being set and X not running. Then it will try to launch an X application.
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