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
" 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
";
	   }

       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 v5.16.2							    2012-10-25							   File::Find(3pm)