unixdev.net


Switch to SpeakEasy.net DSL

The Modular Manual Browser

Home Page
Manual: (OpenBSD-3.6)
Page:
Section:
Apropos / Subsearch:
optional field



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


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 differ-
       ences.

       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 subrou-
           tine.  (See below for details on how to use the
           &wanted function).  Additionally, for each directory
           found, it will "chdir()" into that directory and con-
           tinue 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 function" below.

       Here are the possible keys for the hash:



perl v5.8.5                 2002-11-06                          1





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


       "wanted"
          The value should be a code reference.  This code refer-
          ence 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 refer-
          ence 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, numeri-
          cally, 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  _.

          *     There is a variable $File::Find::fullname which
                holds the absolute pathname of the file with all
                symbolic links resolved

       "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,



perl v5.8.5                 2002-11-06                          2





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


          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.

       "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 sec-
          ond 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 dupli-
          cate files and directories but to proceed normally oth-
          erwise.

       "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 sym-
          bolic 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 regu-
          lar 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.





perl v5.8.5                 2002-11-06                          3





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


       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 func-
       tion, 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 concatena-
       tion 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,




perl v5.8.5                 2002-11-06                          4





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


           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 mag-
       ical filehandle that caches the information from the pre-
       ceding "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 warn-
       ings 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 direc-
         tories. 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.



perl v5.8.5                 2002-11-06                          5





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


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

           o   The path separator is ':', not '/', and the cur-
               rent directory is denoted as ':', not '.'. You
               should be careful about specifying relative path-
               names.  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.

           o   $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::full-
               name, which holds the absolute pathname of that
               directory with all symbolic links resolved, may or
               may not end with a ':'.

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

           o   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







perl v5.8.5                 2002-11-06                          6





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


                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 "Set-
               FileInfo(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 "vir-
               tual" 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 v5.8.5                 2002-11-06                          7