| File::Path - Create or remove directory trees |
File::Path - Create or remove directory trees
This document describes version 2.06 of File::Path, released 2008-05-08.
use File::Path;
# modern
mkpath( 'foo/bar/baz', '/zug/zwang', {verbose => 1} );
rmtree(
'foo/bar/baz', '/zug/zwang',
{ verbose => 1, error => \my $err_list }
);
# traditional
mkpath(['/foo/bar/baz', 'blurfl/quux'], 1, 0711);
rmtree(['foo/bar/baz', 'blurfl/quux'], 1, 1);
The mkpath function provides a convenient way to create directories
of arbitrary depth. Similarly, the rmtree function provides a
convenient way to delete an entire directory subtree from the
filesystem, much like the Unix command rm -r.
Both functions may be called in one of two ways, the traditional, compatible with code written since the dawn of time, and modern, that offers a more flexible and readable idiom. New code should use the modern interface.
The modern way of calling mkpath and rmtree is with a list
of directories to create, or remove, respectively, followed by an
optional hash reference containing keys to control the
function's behaviour.
mkpathThe following keys are recognised as parameters to mkpath.
The function returns the list of files actually created during the
call.
my @created = mkpath(
qw(/tmp /flub /home/nobody),
{verbose => 1, mode => 0750},
);
print "created $_\n" for @created;
umask. If the
directory already exists (and thus does not need to be created),
the permissions will not be modified.
mask is recognised as an alias for this parameter.
mkpath to print the name of each directory
as it is created. By default nothing is printed.
If this parameter is not used, certain error conditions may raise
a fatal error that will cause the program will halt, unless trapped
in an eval block.
rmtreermtree to print the name of each file as
it is unlinked. By default nothing is printed.
rmtree to skip the files
for which the process lacks the required privileges needed to delete
files, such as delete privileges on VMS. In other words, the code
will make no attempt to alter file permissions. Thus, if the process
is interrupted, no filesystem object will be left in a more
permissive mode.
rmtree( '/tmp', {keep_root => 1} );
undef).
rmtree( '/tmp', {result => \my $list} );
print "unlinked $_\n" for @$list;
This is a useful alternative to the verbose key.
Removing things is a much more dangerous proposition than
creating things. As such, there are certain conditions that
rmtree may encounter that are so dangerous that the only
sane action left is to kill the program.
Use error to trap all that is reasonable (problems with
permissions and the like), and let it die if things get out
of hand. This is the safest course of action.
The old interfaces of mkpath and rmtree take a reference to
a list of directories (to create or remove), followed by a series
of positional, numeric, modal parameters that control their behaviour.
This design made it difficult to add additional functionality, as well as posed the problem of what to do when the calling code only needs to set the last parameter. Even though the code doesn't care how the initial positional parameters are set, the programmer is forced to learn what the defaults are, and specify them.
Worse, if it turns out in the future that it would make more sense to change the default behaviour of the first parameter (for example, to avoid a security vulnerability), all existing code will remain hard-wired to the wrong defaults.
Finally, a series of numeric parameters are much less self-documenting in terms of communicating to the reader what the code is doing. Named parameters do not have this problem.
In the traditional API, mkpath takes three arguments:
mkpath to print the
name of each directory as it is created (defaults to FALSE), and
the numeric mode to use when creating the directories (defaults to
0777), to be modified by the current umask.
It returns a list of all directories (including intermediates, determined using the Unix '/' separator) created. In scalar context it returns the number of directories created.
If a system error prevents a directory from being created, then the
mkpath function throws a fatal error with Carp::croak. This error
can be trapped with an eval block:
eval { mkpath($dir) };
if ($@) {
print "Couldn't create $dir: $@";
}
In the traditional API, rmtree takes three arguments:
rmtree to print a
message each time it examines a file, giving the name of the file,
and indicating whether it's using rmdir or unlink to remove
it, or that it's skipping it. (defaults to FALSE)
a boolean value, which if TRUE will cause rmtree to skip any
files to which you do not have delete access (if running under VMS)
or write access (if running under another OS). This will change
in the future when a criterion for 'delete permission' under OSs
other than VMS is settled. (defaults to FALSE)
It returns the number of files, directories and symlinks successfully deleted. Symlinks are simply deleted and not followed.
Note also that the occurrence of errors in rmtree using the
traditional interface can be determined only by trapping diagnostic
messages using $SIG{__WARN__}; it is not apparent from the return
value. (The modern interface may use the error parameter to
record any problems encountered).
If mkpath or rmtree encounter an error, a diagnostic message
will be printed to STDERR via carp (for non-fatal errors),
or via croak (for fatal errors).
If this behaviour is not desirable, the error attribute may be
used to hold a reference to a variable, which will be used to store
the diagnostics. The result is a reference to a list of hash
references. For each hash reference, the key is the name of the
file, and the value is the error message (usually the contents of
$!). An example usage looks like:
rmtree( 'foo/bar', 'bar/rat', {error => \my $err} );
for my $diag (@$err) {
my ($file, $message) = each %$diag;
print "problem unlinking $file: $message\n";
}
If no errors are encountered, $err will point to an empty list
(thus there is no need to test for undef). If a general error
is encountered (for instance, rmtree attempts to remove a directory
tree that does not exist), the diagnostic key will be empty, only
the value will be set:
rmtree( '/no/such/path', {error => \my $err} );
for my $diag (@$err) {
my ($file, $message) = each %$diag;
if ($file eq '') {
print "general error: $message\n";
}
}
File::Path blindly exports mkpath and rmtree into the
current namespace. These days, this is considered bad style, but
to change it now would break too much code. Nonetheless, you are
invited to specify what it is you are expecting to use:
use File::Path 'rmtree';
The functions detect (as far as possible) which way they are being called and will act appropriately. It is important to remember that the heuristic for detecting the old style is either the presence of an array reference, or two or three parameters total and second and third parameters are numeric. Hence...
mkpath 486, 487, 488;
... will not assume the modern style and create three directories, rather it will create one directory verbosely, setting the permission to 0750 (488 being the decimal equivalent of octal 750). Here, old style trumps new. It must, for backwards compatibility reasons.
If you want to ensure there is absolutely no ambiguity about which way the function will behave, make sure the first parameter is a reference to a one-element list, to force the old style interpretation:
mkpath [486], 487, 488;
and get only one directory created. Or add a reference to an empty parameter hash, to force the new style:
mkpath 486, 487, 488, {};
... and hence create the three directories. If the empty hash reference seems a little strange to your eyes, or you suspect a subsequent programmer might helpfully optimise it away, you can add a parameter set to a default value:
mkpath 486, 487, 488, {verbose => 0};
There were race conditions 1.x implementations of File::Path's
rmtree function (although sometimes patched depending on the OS
distribution or platform). The 2.0 version contains code to avoid the
problem mentioned in CVE-2002-0435.
See the following pages for more information:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=286905 http://www.nntp.perl.org/group/perl.perl5.porters/2005/01/msg97623.html http://www.debian.org/security/2005/dsa-696
Additionally, unless the safe parameter is set (or the
third parameter in the traditional interface is TRUE), should a
rmtree be interrupted, files that were originally in read-only
mode may now have their permissions set to a read-write (or ``delete
OK'') mode.
FATAL errors will cause the program to halt (croak), since the
problem is so severe that it would be dangerous to continue. (This
can always be trapped with eval, but it's not a good idea. Under
the circumstances, dying is the best thing to do).
SEVERE errors may be trapped using the modern interface. If the they are not trapped, or the old interface is used, such an error will cause the program will halt.
All other errors may be trapped using the modern interface, otherwise
they will be carped about. Program execution will not be halted.
mkpath was unable to create the path. Probably some sort of
permissions error at the point of departure, or insufficient resources
(such as free inodes on Unix).
path(s) specifiedmkpath was not given any paths to create. This message is only
emitted if the routine is called with the traditional interface.
The modern interface will remain silent if given nothing to do.
mkpath gives you this warning, it may mean that
you have exceeded your filesystem's maximum path length.
rmtree attempted to determine the initial directory by calling
Cwd::getcwd, but the call failed for some reason. No attempt
will be made to delete anything.
rmtree attempted to stat the initial directory (after having
successfully obtained its name via getcwd), however, the call
failed for some reason. No attempt will be made to delete anything.
rmtree attempted to set the working directory in order to
begin deleting the objects therein, but was unsuccessful. This is
usually a permissions issue. The routine will continue to delete
other things, but this directory will be left intact.
rmtree recorded the device and inode of a directory, and then
moved into it. It then performed a stat on the current directory
and detected that the device and inode were no longer the same. As
this is at the heart of the race condition problem, the program
will die at this point.
rmtree attempted to change the permissions on the current directory
to ensure that subsequent unlinkings would not run into problems,
but was unable to do so. The permissions remain as they were, and
the program will carry on, doing the best it can.
rmtree tried to read the contents of the directory in order
to acquire the names of the directory entries to be unlinked, but
was unsuccessful. This is usually a permissions issue. The
program will continue, but the files in this directory will remain
after the call.
rmtree, after having deleted everything in a directory, attempted
to restore its permissions to the original state but failed. The
directory may wind up being left behind.
The solution is to chdir out of the child directory to a place
outside the directory tree to be removed.
rmtree, after having deleted everything and restored the permissions
of a directory, was unable to chdir back to the parent. The program
halts to avoid a race condition from occurring.
rmtree was unable to stat the parent directory after have returned
from the child. Since there is no way of knowing if we returned to
where we think we should be (by comparing device and inode) the only
way out is to croak.
rmtree returned from deleting files in a child directory, a
check revealed that the parent directory it returned to wasn't the one
it started out from. This is considered a sign of malicious activity.
rmtree attempted to set the permissions
on the directory to ensure it could be removed and failed. Program
execution continues, but the directory may possibly not be deleted.
rmtree attempted to remove a directory, but failed. This may because
some objects that were unable to be removed remain in the directory, or
a permissions issue. The directory will be left behind.
rmtree was unable to
restore its permissions from a permissive state back to a possibly
more restrictive setting. (Permissions given in octal).
rmtree attempted to force the permissions of a file to ensure it
could be deleted, but failed to do so. It will, however, still attempt
to unlink the file.
rmtree failed to remove a file. Probably a permissions issue.
rmtree was also unable
to restore the permissions on the file to a possibly less permissive
setting. (Permissions given in octal).
Allows files and directories to be moved to the Trashcan/Recycle
Bin (where they may later be restored if necessary) if the operating
system supports such functionality. This feature may one day be
made available directly in File::Path.
When removing directory trees, if you want to examine each file to decide whether to delete it (and possibly leaving large swathes alone), File::Find::Rule offers a convenient and flexible approach to examining directory trees.
Please report all bugs on the RT queue:
http://rt.cpan.org/NoAuth/Bugs.html
Paul Szabo identified the race condition originally, and Brendan O'Dea wrote an implementation for Debian that addressed the problem. That code was used as a basis for the current code. Their efforts are greatly appreciated.
Tim Bunce and Charles Bailey. Currently maintained by David Landgren <david@landgren.net>.
This module is copyright (C) Charles Bailey, Tim Bunce and David Landgren 1995-2008. All rights reserved.
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
| File::Path - Create or remove directory trees |