Programming Perl, 4th Edition

Files and Filesystems

File path components are separated with / on Unix, with \ on Windows, and with : on the old pre-Unix Macs. Some systems support neither hard links (link) nor symbolic links (symlink, readlink, lstat). Some systems pay attention to capitalization of filenames, some don’t, and some pay attention when creating files but not when reading them. Different systems use different character repertoires.

Here are some tips for writing portable file-manipulating Perl programs:

• The File::Basename module, another platform-tolerant module bundled with Perl, splits a pathname into its components: the base filename, the full path to the directory, and the file suffix:

  use File::Basename;
  
  my $name = basename( $ARGV[0] );
  my $dir  = dirname( $ARGV[0] );
  
  my( $base, $dir, $suffix ) = fileparse( $ARGV[0], qr/\.[^.]+\z/ );

• The standard File::Spec modules provide functions to move around a file system and put path components together properly. Don’t hardcode paths, but construct them:

  use File::Spec::Functions;
  chdir( updir() );        # go up one directory
  $file = catfile( curdir(), "temp", "file.txt" );

  That last line reads in ./temp/file.txt on Unix and Windows or [.temp]file.txt on VMS, and stores the file’s contents in $file.

• The File::HomeDir module from CPAN locates special user directories by detecting your operating system and constructing the right paths for you.

• Use the Path::Class CPAN module for an object-oriented interface to File::Spec that easily allows reading a path from one sort ...