Working with File Systems

This chapter explains:

• How to change the current directory and make a new directory.
• How to use file test operators.
• How to get statistical information of a file.

Working with the Directory Tree

A file system is a tree structure of directories with files associated directories. Perl offers several functions for you to work with the directory tree:

1. chdir() - A function to reset the current directory to a directory identified by the specified path name:

rc = chdir(path_name);

2. mkdir() - A function to make a new directory defined by the specified path name:

rc = mkdir(path_name);

3. rmdir() - A function to remove a directory defined by the specified path name, when the directory is empty:

rc = rmdir(path_name);

4. unlink() - A function to delete a list of files:

rc = unlink(path_name_list);

File Test Operators

Perl offers a number of unary operators to return statistics of a file. Some commonly used ones are:

• "-e path_name" returns 1, if the path name exists.
• "-z path_name" returns 1, if the path name has zero size.
• "-s path_name" returns the size of the path name.
• "-f path_name" returns 1, if the path name is a file.
• "-d path_name" returns 1, if the path name is a directory.
• "-T path_name" returns 1, if the path name is a text file.
• "-B path_name" returns 1, if the path name is a binary file.

Statistics of a File

Instead of using individual file test operators, you can use the stat() function to return a number of statistics of a file. The following program shows you how to use stat():

#- stat.pl
#- Copyright (c) 1995 by Dr. Herong Yang
#
   ($file) = @ARGV;
   die "Missing file name.\n" unless $file;
   ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,
      $atime,$mtime,$ctime,$blksize,$blocks) = stat($file);
   print "dev = $dev\n";
   print "ino = $ino\n";
   print "mode = $mode\n";
   print "nlink = $nlink\n";
   print "uid = $uid\n";
   print "uid = $uid\n";
   print "gid = $gid\n";
   print "rdev = $rdev\n";
   print "size = $size\n";
   print "atime = $atime\n";
   print "mtime = $mtime\n";
   print "ctime = $ctime\n";
   print "blksize = $blksize\n";
   print "blocks = $blocks\n";
   exit;

If you run it on a Windows system, you will get something similar to this:

>stat.pl stat.pl
dev = 3
ino = 0
mode = 33206
nlink = 1
uid = 0
uid = 0
gid = 0
rdev = 3
size = 622
atime = 1069622049
mtime = 1069621972
ctime = 1069621496
blksize =
blocks =