pod2usage question

dwhitney has asked for the wisdom of the Perl Monks concerning the following question:

Hello Monks, I'm having a huge problem with pod2usage in the following code:

#!/usr/bin/perl -w
# 
# $Id: move_data.pl,v 1.12 2005/05/05 21:25:58 dwhitney Exp $

### Declaire script vars ###
use vars qw( $Executable $Transaction );
$|++;    # Turn on autoflush

### Import pre-requisite packages
use Log::Log4perl;
use Getopt::Long qw( GetOptions );
use Cwd qw( chdir realpath );
use Benchmark qw( timestr timediff );
use Pod::Usage qw( pod2usage );
use File::Basename qw( fileparse );
use File::Spec qw( catfile rel2abs );
### Bomb if there is nothing on the command line ###
pod2usage(2) if ( not @ARGV );

my @cmd;
my $LIBPATH;

BEGIN {
    use strict;
    use warnings;
    @cmd = fileparse( File::Spec->rel2abs( $0 ), '\.[^.]*' );
    $LIBPATH = File::Spec->catdir( $cmd[1], "../lib" );
    eval " use lib '$LIBPATH'";
    chdir "$LIBPATH";
    
    use Data::Dumper;
    printf "---ENV---\n%s\n", Dumper( \%ENV );
    
}
[download]

When I execute this command and once the ENV gets printed, I get this error:

Can't open ./move_data.pl for reading: No such file or directory
 at ./move_data.pl line 18
[download]

That's the 'pod2usage(2) if ( not @ARGV );' line.
What did I do?
Where did I hoze this?
Thanks!
Update: Well, I've tried all of these sugestions and I get nothin. Well, the script works just find, just no help.
I love Perl, but stuff like this makes me want to go kill my self....
Thank you all for your suggestions and advice.

Comment on pod2usage question Select or Download Code

Replies are listed 'Best First'.
Re: pod2usage question by tlm (Prior) on May 06, 2005 at 22:16 UTC
The problem is that in the `BEGIN` block your script `chdir`s to a different directory from where you invoked the script, so, by the time that `pod2usage` is executed, the value returned by `$0` (which `pod2usage` relies on) no longer points to the script. This is an easy problem to fix, but I don't understand why your script is `chdir`-ing in the first place. the lowliest monk	[reply]
Re^2: pod2usage question by dwhitney (Beadle) on May 06, 2005 at 23:31 UTC
Well, I've changed by BEGIN block as follows: `BEGIN { use strict; use warnings; print "I am here!\n"; use Pod::Usage qw( pod2usage ); ### Bomb if there is nothing on the command line ### pod2usage(2) if ( not @ARGV ); print "I am there!\n"; @cmd = fileparse( File::Spec->rel2abs( $0 ), '\.[^.]*' ); $LIBPATH = File::Spec->catdir( $cmd[1], "../lib" ); eval " use lib '$LIBPATH'"; chdir "$LIBPATH"; use Data::Dumper; printf "---ENV---\n%s\n", Dumper( \%ENV ); }` [download] Now here's the funky part, on a Win32 box, I get the output: `I am here! Usage: move_data.pl [options] Options: -help..........Brief help message -man...........Full documentation -config........Full path to the configuration file` [download] Which is what I expected, while on a Linux machine, I only get the I am here!... What gives?	[reply] [d/l] [select]
Re^3: pod2usage question by saintmike (Vicar) on May 07, 2005 at 19:39 UTC
Which is what I expected, while on a Linux machine, I only get the I am here!... Odd, works just fine for me. Maybe you should try running it in the debugger. Since the relevant code is in a BEGIN block, you need to put `BEGIN { $DB::single = 1; ...` [download] in there to make sure the debugger doesn't just jump over it. Then, call `$ perl -d move_data.pl` [download] from the command line and step through the source lines using `n` and `s`.	[reply] [d/l] [select]
Re: pod2usage question by phaylon (Curate) on May 06, 2005 at 21:15 UTC
Check your file permissions. pos2usage tries to read the current file to get the POD out of it. hth, p Ordinary morality is for ordinary people. -- Aleister Crowley	[reply]
Re^2: pod2usage question by dwhitney (Beadle) on May 06, 2005 at 21:28 UTC
That's what I thought. Currently the script is set to: -rwxr-xr-x Should I open up the w as well?	[reply]
Re^3: pod2usage question by DaWolf (Curate) on May 06, 2005 at 22:14 UTC
Apparently not, since the error is about reading: Can't open ./move_data.pl for reading: No such file or directory at ./move_data.pl line 18 Er Galvão Abbott www.galvao.eti.br Porto Alegre Perl Mongers	[reply]
Re: pod2usage question by SolidState (Scribe) on May 08, 2005 at 12:27 UTC
As others have pointed out, your problem seems to stem from the chdir command. Your solution involved placing yet more stuff into the BEGIN block where the chdir is. My question is - why use a BEGIN block here in the first place? A BEGIN block is used when you want something to happen at compile time. In your case, you have "use" statements that take place anyway at compile time - so why place them in a BEGIN block? You also run a few other commands that may or may not benefit from being run at compile time - I can't tell. But from what I see, you would gain more clarity if you moved everything in the BEGIN block to the body of the program. Just my 2 cents worth...	[reply]
Re^2: pod2usage question by dwhitney (Beadle) on May 09, 2005 at 17:49 UTC
The Big Reason(TM) for the BEGIN block is to allow for use'ing the MoveDataTools package in a dynamic way. For example, we don't really know where the user installed this script, but we do know where the libs were installed in relation to the script. The BEGIN block is there to help figure out the correct LIB path, based on the script's path. I am also trying to keep this seperate from the local perl install to avoid poluting it with extra stuff, that we don't really want to give global access to. This whole thing is really weird because it works fine on the Windows box I built this on, and except for the pod2usage call works fine on a linux machine as well. Bummer! In any case, thank you all for your input on this!	[reply]
Re^3: pod2usage question by SolidState (Scribe) on May 10, 2005 at 13:05 UTC
The BEGIN block is there to help figure out the correct LIB path, based on the script's path. The FindBin module might here you there. Check out the synopsys examples. Regarding the Pod::Usage problem, what happens if you move the "use Pod::Usage" line outside (before) the BEGIN block? Does that help? HTH :-)	[reply]
Re: pod2usage question by dwhitney (Beadle) on May 10, 2005 at 18:19 UTC
Hello all, I've changed my BEGIN block, to look like: #!/usr/bin/perl -w # # $Id: move_data.pl,v 1.12 2005/05/05 21:25:58 dwhitney Exp $ ### Declaire script vars ### use vars qw( $Executable $Transaction @cmd $LIBPATH ); $\|++; # Turn on autoflush ### Import pre-requisite packages use strict; use warnings; use Log::Log4perl; use Getopt::Long qw( GetOptions ); use Cwd qw( chdir realpath ); use Benchmark qw( timestr timediff ); use File::Basename qw( fileparse ); use File::Spec qw( catfile rel2abs ); use Pod::Usage qw( pod2usage ); ### Bomb if there is nothing on the command line ### pod2usage(2) if ( not @ARGV ); BEGIN { $LIBPATH = "../lib"; @cmd = fileparse( File::Spec->rel2abs( $0 ), '\.[^.]*' ); $LIBPATH = File::Spec->catdir( $cmd[1], "$LIBPATH" ); eval " use lib '$LIBPATH'"; } ### Use the MoveDataTools package ### use MoveDataTools; [download] Problem is, it still does not display any of the usage info in a Linux env. Good speed increase, but no man or help.... Bummer!	[reply] [d/l]
Re^2: pod2usage question by Anonymous Monk on Jun 11, 2006 at 13:45 UTC
Hello all, Same problem, resolved by converting the script file to unix end-of-line with dos2unix.	[reply]
Re^3: pod2usage question by planetscape (Chancellor) on Jun 11, 2006 at 20:21 UTC
Ah, yes. This has given me problems before, often with Unix-style programs operating on DOS-style data. Good to remember to check for these sorts of issues. In the quest for a utility to convert between *nix and DOS newlines on a regular basis, I have found flip: Newline conversion between Unix, Macintosh and MS-DOS ASCII files to be useful. It not only converts between DOS and Unix file formats, but also includes a handy `-t` command-line switch to tell you which format a given file uses. HTH, planetscape	[reply] [d/l]


Perl: the Markov chain saw
	PerlMonks