error on file open

maynard517 has asked for the wisdom of the Perl Monks concerning the following question:

I get this error: Permission denied error on open - PS17 at cp165.pl line 22. executing the following code

#*** This script reads the PS17 file and writes it to    ***
#*** the folder 'archive' and also overwrites 'COMDATA'  ***
use strict;
use warnings;

my ($d,$m,$y)=(localtime)[3,4,5];
my $date= sprintf '%02d%02d%02d', $m+1,$d, $y+1900;
#  my $newame='XM712.XM712.PS00017.', $date;
my $threenodes='XM712.XM712.PS00017';
#  my DIR = dir("f:\\lawprod\\law\\prd9\\work\\COMDATAFILE\\IN\\");

open_files ();

#***   reads the COMDATAFILE/IN directory   ***
while (my $FILENAME = readdir(DIR) ) {
    print "filename: $FILENAME\n";
    my $comp_name = substr($FILENAME, 0, 19);
    print "comp_name: $comp_name\n";
    print "threenodes: $threenodes\n";
    while ($comp_name == $threenodes) {
        print "dir: DIR\n";
        open (PS17, "$FILENAME") or die "$! error on open - PS17";
        read_and_write ();
        }
[download]

I am very new to Perl, and don't know how to debug this error. Thank you.

Comment on error on file open Download Code

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Re: error on file open by GrandFather (Saint) on Nov 25, 2013 at 22:36 UTC
Change your open (and following) line to: `open my $PS17, '<', $FILENAME or die "$! error on open - $FILENAME"; read_and_write ($PS17);` [download] That doesn't fix the problem, but it gives better diagnostics (you know what was being opened), avoids potential problems with some file names by making the open mode explicit, and better manages the lifetime of the file handle. You'll need to update read_and_write to take the file handle as a parameter. True laziness is hard work	[reply] [d/l]
Re: error on file open by choroba (Cardinal) on Nov 25, 2013 at 22:19 UTC
Try printing out $FILENAME. Note that `==` compares numerically, so strings not starting with numbers are usually equal (0 == 0). Also, note that readdir returns both files and directories, and that it returns only their names, not full paths. لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ	[reply] [d/l]
Re: error on file open by Anonymous Monk on Nov 25, 2013 at 22:41 UTC
I am very new to Perl, and don't know how to debug this error There are checklists for that , I use them all the time (don't be fooled by the titles), Basic debugging checklist , brian's Guide to Solving Any Perl Problem, CGI Help Guide , Troubleshooting Perl CGI scripts ... More generic advice :) On debugging, verify everything, talk to teddybear ... checklists and more , perltrap, perltrap, Common Perl Pitfalls / perltrap "permission denied" is about as clear as it can get: Q: can I have this cookie? A: No. its because readdir does NOT return the complete path and you forgot to chdir readdir is very low level, if you use Path::Tiny it can even do the die-ing for you, ex `$ perl -e " use Path::Tiny qw/ path /; path(qw/./)->openrw_raw; " Error open (+<:raw) on '.': Permission denied at -e line 1.` [download] Then you can write functions that take arguments like this `#!/usr/bin/perl -- use strict; use warnings; use POSIX(); use Path::Tiny qw/ path /; Main( @ARGV ); exit( 0 ); sub Main { my $date = POSIX::strftime('%Y-%m-%d', localtime); my $dirp = path( 'f:/lawprod/law/prd9/work/COMDATAFILE/IN/' ); my $diri = $dirp->iterator( { qw/ recurse 0 / }); while( my $file = $diri->() ){ if( $file =~ /^\Q$threenodes\E/ ){ FrobnicateInnoculate( $file->openrw_raw ); } } } sub FrobnicateInnoculate { my( $filehandle ) = @_; ... close $filehandle; }` [download] `cpan Path::Tiny` perlintro#Simple matching, quotemeta, eq for string comparison not == (because perlnumber), http://p3rl.orrg/POSIX#strftime chromatics free book Modern Perl a loose description of how experienced and effective Perl 5 programmers work....You can learn this too. Learn Perl in about 2 hours 30 minutes Beginning Perl (free) Chapter 6: Files and Data	[reply] [d/l] [select]
Re: error on file open by wazat (Monk) on Nov 26, 2013 at 05:47 UTC
Others have addresed the main issues in your program., but I thought I would point out that the first file returned is likely "." followed by ".." Also, I don't understand why you base your loop on a comparison of $comp_name and $threenodes. These do not appear to change within the while loop. If it didn't die, it looks like an infinite loop.	[reply]
Re: error on file open by hexcoder (Curate) on Nov 26, 2013 at 15:28 UTC
One other point, I have not seen mentioned yet: `open $PS17, $FILENAME` or `open my $PS17, '<', $FILENAME` open the file only for read access. If you really intend to `read_and_write()` the opened file, you need to say something like `open my $FS17, '+<', $FILENAME or die "$! error on open $FILENAME\n"` Hope that helps!	[reply] [d/l] [select]