Man Pages

File::Find(3) - phpMan File::Find(3) - phpMan

Command: man perldoc info search(apropos)  


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 is 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 func-
       tion" 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 fol-
          low_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 fol-
                low_fast are not set.

          *     There is a variable $File::Find::fullname which holds the absolute pathname of the file with all sym-
                bolic 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, how-
          ever.  Since only symbolic links have to be hashed, this is much cheaper both in space and time.  If pro-
          cessing 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.

       Don't modify these variables.

       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 sum-
       marizes 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 spec-
       ified, 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 warn-
       ings 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 direc-
         tory 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 sym-
               bolic 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" desk-
               top, 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 v5.8.8                       2001-09-21                     File::Find(3)