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

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. The &wanted subroutine is mandatory.

       "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:

	  o	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.

	  o	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 affecting 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.

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.

SEE ALSO
       find, find2perl.

perl v5.16.3				    2013-03-04				  File::Find(3pm)
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