Quick Navigation Bar
regular expressions :: files and directories :: process management
[ toc | forums ]

Note: If the document URL does not begin with https://randu.org/tutorials/perl/ then you are viewing a copy. Please direct your browser to the correct location for the most recent version.

Manipulating Files and Directories

Building on the previous File I/O section, we will now look at how we can modify various directory and file properties.

Manipulating Directories :: Directory Access

If you want to change directories you can issue the chdir command:

  chdir("/some/path") || die "Cannot chdir to /some/path ($!)";

In order to glob a list, you can do it in either of these two ways:
```
  @a = </some/path/*.c>
  @a = glob("/some/path/*.c");
```
This would create a list of all of the .c files in the /some/path directory. We could loop through a glob directly by:
```
  if (-d "/some/path") {
    $where = "/some/path";
  } else {
    $where = "/another/path";
  }
  while (defined($next = <$where/*.c>)) {
    print "found a c file in $where directory named $name\n";
  }
```
Notice we used the -d check for a directory for its existence. Very powerful indeed.

Manipulating Directories :: Directory Handles

Just like we can create file handles for our files, we can create directory handles for our directories!

Using Directory Handles:

  opendir(DIRHANDLE, "/some/path") || die "Cannot opendir /some/path: $!";
  foreach $name (sort readdir(DIRHANDLE)) {
    print "found file: $name\n";
  }
  closedir(DIRHANDLE);

This prints out a sorted directory listing. For an unsorted list, we could have simplified the loop construct:

  while ($name = readdir(DIRHANDLE)) {
    print "found file: $name\n";
  }

Remember to close your directory handles!

Manipulating Directories :: Creating and Removing Directories

There is no trick to creating and removing directories in Perl:
```
  mkdir("newdir", 0755) || die "Cannot mkdir newdir: $!";
  rmdir("olddir") || dir "Cannot rmdir olddir: $!";
```
Notice the 0755 in the mkdir function call is permission bits. A quick rundown: 4 = read, 5 = read + execute, 6 = read + write, 7 = read + write + execute. You need to set the execute bit on in order for you to access the directory.

Manipulating Files :: Removing and Renaming Files

Removing files can be done by using the unlink function:
```
  print "file to delete? ";
  chomp($name = <STDIN>);
  unlink($name) || die "Cannont unlink $name: $!";
```
You can even give unlink a glob or a list of files to delete.

Renaming files is a simple function call:

  rename("oldfilename.txt", "newfilename.txt") || die "Cannot rename file.txt: $!";
  rename("data.in", "/some/new/path/data.in") || die "Cannot rename data.in: $!";

Notice that Perl's rename function is almost the same as the mv command under *NIX.

Manipulating Files :: Linking

To create a symbolic link under Perl, use the symlink function:

  # Under *NIX shell:
  ln -s file.txt /some/other/path/reference.txt
  # Under Perl:
  symlink("file.txt", "/some/other/path/reference.txt") || die "Cannot symlink file.txt: $!";

Perl gives us a way to read symlinks:

  if (defined($x = readlink("reference.txt"))) {
    print "reference.txt points at '$x'\n";
  }

Manipulating Files :: Modifying Permissions

Modifying permissions is very similar to the shell chmod command:
```
  chmod(0644, "file1", "file2") || die "Cannot chmod file1, file2: $!";
```
Notice we can give a list of files to the chmod command (as we have seen with other File/Dir modification functions.

Manipulating Files and Directories Review

Perl proves again to be a swiss army knife of programming languages. We can modify our directories and files with ease, while ther Perl interpreter takes care of the gory details.

Notice: Please do not replicate or copy these pages and host them elsewhere. This is to ensure that the latest version can always be found here.

Disclaimer: The document author has published these pages with the hope that it may be useful to others. However, the document author does not guarantee that all information contained on these webpages are correct or accurate. There is no warranty, expressed or implied, of merchantability or fitness for any purpose. The author does not assume any liability or responsibility for the use of the information contained on these webpages.

If you see an error, please send an email to the address below indicating the error. Your feedback is greatly appreciated and will help to continually improve these pages.