Get a DH from <STDIN>?

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

Hi Monks: I get an error that says "readdir() attempted on invalid dirhandle DH" from the code below, so what do I do, Thanks, Chet:

#!/usr/bin/perl
use strict;
use warnings;

my $outputfile ="Test_PDB_ID_list.txt";
my $four_char_PDB_ID='';
open (PDB_IDs,">", "$outputfile");
my $PDB_ID= '';

my $dir_to_process= '';
print "What is the directory to process?";

$dir_to_process = <STDIN>;
#$dir_to_process = "Targets-IonChannel";-if I used this #line it would
+ work
#open the folder
unless (opendir(DH, $dir_to_process)){
    print "Cannot open folder $dir_to_process!\n";
    
}
print "$dir_to_process\n";
foreach $PDB_ID (readdir DH){
    $four_char_PDB_ID =substr($PDB_ID,0,4);
    print PDB_IDs "$four_char_PDB_ID\n";
    print "$four_char_PDB_ID \n";
    
    
};

exit;
[download]

What is the directory to process?

Targets-IonChannel

Cannot open folder

Targets-IonChannel

readdir() attempted on invalid dirhandle DH at C:\Users\cseligman\Documents\Eclipseworkspace\DrugTargets\GetPDBnames-1.pl line 21, <STDIN> line 1.

Comment on Get a DH from <STDIN>? Download Code

Replies are listed 'Best First'.
Re: Get a DH from <STDIN>? by ikegami (Patriarch) on Mar 29, 2011 at 17:11 UTC
Of course you cannot read from a handle you never opened ("Cannot open folder"). The reason it failed to open is that you failed to remove the trailing newline from the line you read from STDIN. `chomp` it. By the way, it's a good idea to also include `$!` in error messages from `open` and `opendir`.	[reply] [d/l] [select]
Re: Get a DH from <STDIN>? by wind (Priest) on Mar 29, 2011 at 17:10 UTC
When opendir fails, you should die and examine the error message. `opendir(DH, $dir_to_process) or die "Cannot open $dir_to_process: $!";` [download] Most likely you just need to chomp your input string `my $dir_to_process = <STDIN>; chomp $dir_to_process;` [download]	[reply] [d/l] [select]
Re: Get a DH from <STDIN>? by jethro (Monsignor) on Mar 29, 2011 at 17:12 UTC
Add a `chomp($dir_to_process);` and it should work. Also you might change the 'print "Cannot...' to 'die "Cannot....'. If you can't open the dir then there is no reason to continue	[reply] [d/l]
Re: Get a DH from <STDIN>? by Anonymous Monk on Mar 29, 2011 at 17:09 UTC
so what do I do, When your program fails to open a directory handle, wait for it :), do NOT try to read from it, because the opendir call failed :)	[reply]
Re: Get a DH from <STDIN>? by jpl (Monk) on Mar 29, 2011 at 17:50 UTC
The newline is still attached to the directory name. You'll want to `chomp($dir_to_process);` [download] before attempting the opendir.	[reply] [d/l]