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Reading regex from a file...

grellsworth
New User

Apr 11, 2008, 1:17 PM

Post #1 of 8 (5563 views)

Reading regex from a file...	Can't Post

given the line:

/home/user/images s#^(.*)\.jpg$#$1\.JPG#g

I would like to use opendir and readdir to generate an array of entries for the path /home/user/images and then use the regex to change each entry that ends with ".jpg" to "<whatever>.JPG".

My code follows

Code

sub regexrename 
{ 
   my($basedir, $expr) = @_; 
 
   print "$basedir $expr\n"; 
 
   opendir(DIR, $basedir); 
   my(@entries) = grep(!/^\.\.?$/, readdir(DIR)); 
   closedir(DIR); 
 
   foreach $entry ( @entries ) 
   { 
      chomp($entry); 
      $entry =~ $expr; 
      print "$entry\n"; 
   } 
}

Given that $basedir and $expr are being set to the proper values, why does this code not work?

Code

$basedir == "/home/usr/images" == true! 
$expr == "s#^(.*)\.jpg$#$1\.JPG#g" == true!

Any help is greatly appreciated.

Sincerely,

Gordon E.

KevinR
Veteran

Apr 11, 2008, 2:32 PM

Post #2 of 8 (5562 views)

Re: [grellsworth] Reading regex from a file... [In reply to]	Can't Post

What is this line supposed to be?

$entry =~ $expr;

What is $expr?
-------------------------------------------------

grellsworth
New User

Apr 11, 2008, 3:08 PM

Post #3 of 8 (5558 views)

Re: [KevinR] Reading regex from a file... [In reply to]	Can't Post

Quote

given the line:

/home/user/images s#^(.*)\.jpg$#$1\.JPG#g

In Reply To

If the above line is read from a file and then split at the space,
then the two parts are fed into the regexrename subroutine, something like this:

Code

regexrename($part[0], $part[1]); 
 
sub regexrename  
{  
   my($basedir, $expr) = @_;  
  
   print "$basedir $expr\n";  
  
   opendir(DIR, $basedir);  
   my(@entries) = grep(!/^\.\.?$/, readdir(DIR));  
   closedir(DIR);  
  
   foreach $entry ( @entries )  
   {  
      chomp($entry);  
      $entry =~ $expr;  
      print "$entry\n";  
   }  
}

then $part[0] would become $basename and $part[1] would become $expr, wouldn't it?

Quote

$basename == /home/user/images
$expr == s#^(.*)\.jpg$#$1\.JPG#g

Gordon E.

KevinR
Veteran

Apr 11, 2008, 3:42 PM

Post #4 of 8 (5556 views)

Re: [grellsworth] Reading regex from a file... [In reply to]	Can't Post

Quote

then $part[0] would become $basename and $part[1] would become $expr, wouldn't it?

Yes it would but the regexp will not work like you have it. It would be better to use the qr operator to quote the regexp.

Untested code:

Code

my $line = '/home/user/images s#^(.*)\.jpg$#$1\.JPG#g'; 
@part = split(/\s/,$line); 
$part[1] = qr{$part[1]}; 
 
regexrename($part[0], $part[1]);  
  
sub regexrename   
{   
   my($basedir, $expr) = @_;   
   
   print "$basedir $expr\n";   
   
   opendir(DIR, $basedir);   
   my(@entries) = grep(!/^\.\.?$/, readdir(DIR));   
   closedir(DIR);   
   
   foreach $entry ( @entries )   
   {   
      chomp($entry);   
      $entry =~ $expr;   
      print "$entry\n";   
   }   
}

See if that works.
-------------------------------------------------

grellsworth
New User

Apr 11, 2008, 5:54 PM

Post #5 of 8 (5553 views)

Re: [KevinR] Reading regex from a file... [In reply to]	Can't Post

Code

#!/usr/bin/perl -w 
my $line = '/home/user/images s#^(.*)\.jpg$#$1\.JPG#g'; 
@part = split(/\s/,$line); 
$part[1] = qr{$part[1]}; 
 
regexrename($part[0], $part[1]); 
 
sub regexrename 
{ 
   my($basedir, $expr) = @_; 
 
   print "$basedir $expr\n"; 
 
   opendir(DIR, $basedir); 
   my(@entries) = grep(!/^\.\.?$/, readdir(DIR)); 
   closedir(DIR); 
 
   foreach $entry ( @entries ) 
   { 
      chomp($entry); 
      $entry =~ $expr; 
      print "$entry\n"; 
   } 
}

/home/user/images contents (BEFORE)

Quote

afile.jpg
Bfile.jpg
cFile.jpg
dfIle.jpg
efiLe.jpg

When executing the script, the only output I get is:

Quote

afile.jpg
Bfile.jpg
cFile.jpg
dfIle.jpg
efiLe.jpg

And when I check the directory contents again, they haven't changed... they are still all *.jpg (all lower-case).

I really appreciate your help so far!

Thank You,

Gordon E.

KevinR
Veteran

Apr 12, 2008, 12:11 AM

Post #6 of 8 (5546 views)

Re: [grellsworth] Reading regex from a file... [In reply to]	Can't Post

If you want to change the names of files you have to use the rename() function. Reading the file into an array and changing them in the array only changes the names/variables stored in the array, not the file names stored on disk. Now that I think about it, I am not sure you can quote a substitution regexp s///, maybe qr only supports m//. But there is no need to pass the entire regexp into your function to rename jpg files to JPG. Just pass in the jpg extension and use that in a regxp.
-------------------------------------------------

grellsworth
New User

Apr 12, 2008, 3:32 PM

Post #7 of 8 (5541 views)

Re: [KevinR] Reading regex from a file... [In reply to]	Can't Post

In Reply To

I grant you that I didn't put the rename commands in, and that's why the files didn't change, but the replace should have taken place in the variables at least, and that did not happen.

The point is not just to simply rename jpg files to JPG, but to allow the USER to use regex to change whatever files however they wish. What if some files were jpg, and some where jpeg and some were JpEg or whatever... regex would provide the power and flexability to rename whatever files the user wished, in a way that the user wanted to change them.

Gordon E.

KevinR
Veteran

Apr 12, 2008, 11:55 PM

Post #8 of 8 (5532 views)

Re: [grellsworth] Reading regex from a file... [In reply to]	Can't Post

Personally I think you are going about it wrong. All you should pass to the script is the current directory where the files are (or chdir into it) and the old file extension and the new file extension, you should not be passing in a regexp, that part should be hard coded into the script.
-------------------------------------------------

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