Страницы справочника OS X

Эта страница руководства для  версии 10.9 Mac OS X

Читать страницы руководства

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:

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