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File::Find(3)	       Perl Programmers Reference Guide		 File::Find(3)

NAME
       File::Find - Traverse a directory tree.

SYNOPSIS
	   use File::Find;
	   find(\&wanted, @directories_to_search);
	   sub wanted { ... }

	   use File::Find;
	   finddepth(\&wanted, @directories_to_search);
	   sub wanted { ... }

	   use File::Find;
	   find({ wanted => \&process, follow => 1 }, '.');

DESCRIPTION
       These are functions for searching through directory trees doing work on
       each file found similar to the Unix find command.  File::Find exports
       two functions, "find" and "finddepth".  They work similarly but have
       subtle differences.

       find
	     find(\&wanted,  @directories);
	     find(\%options, @directories);

	   "find()" does a depth-first search over the given @directories in
	   the order they are given.  For each file or directory found, it
	   calls the &wanted subroutine.  (See below for details on how to use
	   the &wanted function).  Additionally, for each directory found, it
	   will "chdir()" into that directory and continue the search,
	   invoking the &wanted function on each file or subdirectory in the
	   directory.

       finddepth
	     finddepth(\&wanted,  @directories);
	     finddepth(\%options, @directories);

	   "finddepth()" works just like "find()" except that it invokes the
	   &wanted function for a directory after invoking it for the
	   directory's contents.  It does a postorder traversal instead of a
	   preorder traversal, working from the bottom of the directory tree
	   up where "find()" works from the top of the tree down.

       %options

       The first argument to "find()" is either a code reference to your
       &wanted function, or a hash reference describing the operations to be
       performed for each file.	 The code reference is described in "The
       wanted function" below.

       Here are the possible keys for the hash:

       "wanted"
	  The value should be a code reference.	 This code reference is
	  described in "The wanted function" below.

       "bydepth"
	  Reports the name of a directory only AFTER all its entries have been
	  reported.  Entry point "finddepth()" is a shortcut for specifying
	  "<{ bydepth =" 1 }>> in the first argument of "find()".

       "preprocess"
	  The value should be a code reference. This code reference is used to
	  preprocess the current directory. The name of the currently
	  processed directory is in $File::Find::dir. Your preprocessing
	  function is called after "readdir()", but before the loop that calls
	  the "wanted()" function. It is called with a list of strings
	  (actually file/directory names) and is expected to return a list of
	  strings. The code can be used to sort the file/directory names
	  alphabetically, numerically, or to filter out directory entries
	  based on their name alone. When follow or follow_fast are in effect,
	  "preprocess" is a no-op.

       "postprocess"
	  The value should be a code reference. It is invoked just before
	  leaving the currently processed directory. It is called in void
	  context with no arguments. The name of the current directory is in
	  $File::Find::dir. This hook is handy for summarizing a directory,
	  such as calculating its disk usage. When follow or follow_fast are
	  in effect, "postprocess" is a no-op.

       "follow"
	  Causes symbolic links to be followed. Since directory trees with
	  symbolic links (followed) may contain files more than once and may
	  even have cycles, a hash has to be built up with an entry for each
	  file.	 This might be expensive both in space and time for a large
	  directory tree. See follow_fast and follow_skip below.  If either
	  follow or follow_fast is in effect:

	  ·	It is guaranteed that an lstat has been called before the
		user's "wanted()" function is called. This enables fast file
		checks involving _.  Note that this guarantee no longer holds
		if follow or follow_fast are not set.

	  ·	There is a variable $File::Find::fullname which holds the
		absolute pathname of the file with all symbolic links
		resolved.  If the link is a dangling symbolic link, then
		fullname will be set to "undef".

	  This is a no-op on Win32.

       "follow_fast"
	  This is similar to follow except that it may report some files more
	  than once.  It does detect cycles, however.  Since only symbolic
	  links have to be hashed, this is much cheaper both in space and
	  time.	 If processing a file more than once (by the user's "wanted()"
	  function) is worse than just taking time, the option follow should
	  be used.

	  This is also a no-op on Win32.

       "follow_skip"
	  "follow_skip==1", which is the default, causes all files which are
	  neither directories nor symbolic links to be ignored if they are
	  about to be processed a second time. If a directory or a symbolic
	  link are about to be processed a second time, File::Find dies.

	  "follow_skip==0" causes File::Find to die if any file is about to be
	  processed a second time.

	  "follow_skip==2" causes File::Find to ignore any duplicate files and
	  directories but to proceed normally otherwise.

       "dangling_symlinks"
	  If true and a code reference, will be called with the symbolic link
	  name and the directory it lives in as arguments.  Otherwise, if true
	  and warnings are on, warning "symbolic_link_name is a dangling
	  symbolic link\n" will be issued.  If false, the dangling symbolic
	  link will be silently ignored.

       "no_chdir"
	  Does not "chdir()" to each directory as it recurses. The "wanted()"
	  function will need to be aware of this, of course. In this case, $_
	  will be the same as $File::Find::name.

       "untaint"
	  If find is used in taint-mode (-T command line switch or if EUID !=
	  UID or if EGID != GID) then internally directory names have to be
	  untainted before they can be chdir'ed to. Therefore they are checked
	  against a regular expression untaint_pattern.	 Note that all names
	  passed to the user's wanted() function are still tainted. If this
	  option is used while not in taint-mode, "untaint" is a no-op.

       "untaint_pattern"
	  See above. This should be set using the "qr" quoting operator.  The
	  default is set to  "qr|^([-+@\w./]+)$|".  Note that the parentheses
	  are vital.

       "untaint_skip"
	  If set, a directory which fails the untaint_pattern is skipped,
	  including all its sub-directories. The default is to 'die' in such a
	  case.

       The wanted function

       The "wanted()" function does whatever verifications you want on each
       file and directory.  Note that despite its name, the "wanted()"
       function is a generic callback function, and does not tell File::Find
       if a file is "wanted" or not.  In fact, its return value is ignored.

       The wanted function takes no arguments but rather does its work through
       a collection of variables.

       $File::Find::dir is the current directory name,
       $_ is the current filename within that directory
       $File::Find::name is the complete pathname to the file.

       The above variables have all been localized and may be changed without
       effecting data outside of the wanted function.

       For example, when examining the file /some/path/foo.ext you will have:

	   $File::Find::dir  = /some/path/
	   $_		     = foo.ext
	   $File::Find::name = /some/path/foo.ext

       You are chdir()'d to $File::Find::dir when the function is called,
       unless "no_chdir" was specified. Note that when changing to directories
       is in effect the root directory (/) is a somewhat special case inasmuch
       as the concatenation of $File::Find::dir, '/' and $_ is not literally
       equal to $File::Find::name. The table below summarizes all variants:

		     $File::Find::name	$File::Find::dir  $_
	default	     /			/		  .
	no_chdir=>0  /etc		/		  etc
		     /etc/x		/etc		  x

	no_chdir=>1  /			/		  /
		     /etc		/		  /etc
		     /etc/x		/etc		  /etc/x

       When <follow> or <follow_fast> are in effect, there is also a
       $File::Find::fullname.  The function may set $File::Find::prune to
       prune the tree unless "bydepth" was specified.  Unless "follow" or
       "follow_fast" is specified, for compatibility reasons (find.pl,
       find2perl) there are in addition the following globals available:
       $File::Find::topdir, $File::Find::topdev, $File::Find::topino,
       $File::Find::topmode and $File::Find::topnlink.

       This library is useful for the "find2perl" tool, which when fed,

	   find2perl / -name .nfs\* -mtime +7 \
	       -exec rm -f {} \; -o -fstype nfs -prune

       produces something like:

	   sub wanted {
	       /^\.nfs.*\z/s &&
	       (($dev, $ino, $mode, $nlink, $uid, $gid) = lstat($_)) &&
	       int(-M _) > 7 &&
	       unlink($_)
	       ||
	       ($nlink || (($dev, $ino, $mode, $nlink, $uid, $gid) = lstat($_))) &&
	       $dev < 0 &&
	       ($File::Find::prune = 1);
	   }

       Notice the "_" in the above "int(-M _)": the "_" is a magical
       filehandle that caches the information from the preceding "stat()",
       "lstat()", or filetest.

       Here's another interesting wanted function.  It will find all symbolic
       links that don't resolve:

	   sub wanted {
		-l && !-e && print "bogus link: $File::Find::name\n";
	   }

       See also the script "pfind" on CPAN for a nice application of this
       module.

WARNINGS
       If you run your program with the "-w" switch, or if you use the
       "warnings" pragma, File::Find will report warnings for several weird
       situations. You can disable these warnings by putting the statement

	   no warnings 'File::Find';

       in the appropriate scope. See perllexwarn for more info about lexical
       warnings.

CAVEAT
       $dont_use_nlink
	 You can set the variable $File::Find::dont_use_nlink to 1, if you
	 want to force File::Find to always stat directories. This was used
	 for file systems that do not have an "nlink" count matching the
	 number of sub-directories.  Examples are ISO-9660 (CD-ROM), AFS, HPFS
	 (OS/2 file system), FAT (DOS file system) and a couple of others.

	 You shouldn't need to set this variable, since File::Find should now
	 detect such file systems on-the-fly and switch itself to using stat.
	 This works even for parts of your file system, like a mounted CD-ROM.

	 If you do set $File::Find::dont_use_nlink to 1, you will notice slow-
	 downs.

       symlinks
	 Be aware that the option to follow symbolic links can be dangerous.
	 Depending on the structure of the directory tree (including symbolic
	 links to directories) you might traverse a given (physical) directory
	 more than once (only if "follow_fast" is in effect).  Furthermore,
	 deleting or changing files in a symbolically linked directory might
	 cause very unpleasant surprises, since you delete or change files in
	 an unknown directory.

NOTES
       ·   Mac OS (Classic) users should note a few differences:

	   ·   The path separator is ':', not '/', and the current directory
	       is denoted as ':', not '.'. You should be careful about
	       specifying relative pathnames.  While a full path always begins
	       with a volume name, a relative pathname should always begin
	       with a ':'.  If specifying a volume name only, a trailing ':'
	       is required.

	   ·   $File::Find::dir is guaranteed to end with a ':'. If $_
	       contains the name of a directory, that name may or may not end
	       with a ':'. Likewise, $File::Find::name, which contains the
	       complete pathname to that directory, and $File::Find::fullname,
	       which holds the absolute pathname of that directory with all
	       symbolic links resolved, may or may not end with a ':'.

	   ·   The default "untaint_pattern" (see above) on Mac OS is set to
	       "qr|^(.+)$|". Note that the parentheses are vital.

	   ·   The invisible system file "Icon\015" is ignored. While this
	       file may appear in every directory, there are some more
	       invisible system files on every volume, which are all located
	       at the volume root level (i.e.  "MacintoshHD:"). These system
	       files are not excluded automatically.  Your filter may use the
	       following code to recognize invisible files or directories
	       (requires Mac::Files):

		use Mac::Files;

		# invisible() --  returns 1 if file/directory is invisible,
		# 0 if it's visible or undef if an error occurred

		sub invisible($) {
		  my $file = shift;
		  my ($fileCat, $fileInfo);
		  my $invisible_flag =	1 << 14;

		  if ( $fileCat = FSpGetCatInfo($file) ) {
		    if ($fileInfo = $fileCat->ioFlFndrInfo() ) {
		      return (($fileInfo->fdFlags & $invisible_flag) && 1);
		    }
		  }
		  return undef;
		}

	       Generally, invisible files are system files, unless an odd
	       application decides to use invisible files for its own
	       purposes. To distinguish such files from system files, you have
	       to look at the type and creator file attributes. The MacPerl
	       built-in functions "GetFileInfo(FILE)" and
	       "SetFileInfo(CREATOR, TYPE, FILES)" offer access to these
	       attributes (see MacPerl.pm for details).

	       Files that appear on the desktop actually reside in an (hidden)
	       directory named "Desktop Folder" on the particular disk volume.
	       Note that, although all desktop files appear to be on the same
	       "virtual" desktop, each disk volume actually maintains its own
	       "Desktop Folder" directory.

BUGS AND CAVEATS
       Despite the name of the "finddepth()" function, both "find()" and
       "finddepth()" perform a depth-first search of the directory hierarchy.

HISTORY
       File::Find used to produce incorrect results if called recursively.
       During the development of perl 5.8 this bug was fixed.  The first fixed
       version of File::Find was 1.01.

perl v5.10.0			  2007-12-18			 File::Find(3)
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