File Tips & Trick in Perl

Here are a few tips & tricks which you may find useful when dealing with files/directories in Perl.

Perl Test Operators

Code:

 +-------------+------------------------------------+
 | Operator    | Function                           |
 +-------------+------------------------------------+
 |-e           | Tests if OPERAND exists.           |
 +-------------+------------------------------------+
 |-f           | Tests if OPERAND is a regular file |
 |             | as opposed to a directory,         |
 |             | symbolic link or other type of file|
 +-------------+------------------------------------+
 |-l           | Tests if OPERAND is a symbolic link|
 +-------------+------------------------------------+
 |-s           | Returns size of OPERAND in bytes   |
 +-------------+------------------------------------+
 |-d           | Tests if OPERAND is a directory.   |
 +-------------+------------------------------------+
 |-T           | Tests if OPERAND is a text file.   |
 +-------------+------------------------------------+
 

Example:

Code:

 #!/usr/bin/perl
 
 if(-e "/tmp/test.pl")
 {
     print "File/directory exists.";
 }
 
 if(-f "/tmp/test.pl")
 {
     print "File exists";
 }
 
 $size = -s "/tmp/test.pl";
 print "Size of /tmp/test.pl is $size bytes";
 

Filtering Files With Some Characteristics

We can use a combination of grep and perl test operators to filter some files out, to match some criteria of ours, like getting only text files.

Code:

 #!/usr/bin/perl
 
 $path = "/tmp/test/";
 opendir(DIR, $path);
 
 @arr1 = readdir DIR;
 @arr2 = grep{-T "$path$_"} @arr1; #only text files only
 @arr3 = grep{!-d "$path$_"} @arr1; #no directories
 @arr4 = grep{-s "$path$_" < 2048} @arr1; #less than 2KB
 @arr5 = grep{/^a/} @arr1; #filenames starting with 'a'
 

Finding the basename of a file from its full path-name

Code:

 #!/usr/bin/perl
 
 use File::Basename;
 
 $path = "/home/htdocs/go4expert.com/cgi-bin/index.cgi";
 $basename = basename($path, ".cgi");
 
 print $basename;
 

Output:

Code:

 index
 

To find just the name of the file, without its preceding path, and minus the "dot extension" using File::Basename module is pretty easy. We just pass it the whole path, and a string that specifies what extension we want removed and presto we're done.