1File::Find(3pm)        Perl Programmers Reference Guide        File::Find(3pm)
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3
4

NAME

6       File::Find - Traverse a directory tree.
7

SYNOPSIS

9           use File::Find;
10           find(\&wanted, @directories_to_search);
11           sub wanted { ... }
12
13           use File::Find;
14           finddepth(\&wanted, @directories_to_search);
15           sub wanted { ... }
16
17           use File::Find;
18           find({ wanted => \&process, follow => 1 }, '.');
19

DESCRIPTION

21       These are functions for searching through directory trees doing work on
22       each file found similar to the Unix find command.  File::Find exports
23       two functions, "find" and "finddepth".  They work similarly but have
24       subtle differences.
25
26       find
27             find(\&wanted,  @directories);
28             find(\%options, @directories);
29
30           "find()" does a depth-first search over the given @directories in
31           the order they are given.  For each file or directory found, it
32           calls the &wanted subroutine.  (See below for details on how to use
33           the &wanted function).  Additionally, for each directory found, it
34           will "chdir()" into that directory and continue the search,
35           invoking the &wanted function on each file or subdirectory in the
36           directory.
37
38       finddepth
39             finddepth(\&wanted,  @directories);
40             finddepth(\%options, @directories);
41
42           "finddepth()" works just like "find()" except that it invokes the
43           &wanted function for a directory after invoking it for the
44           directory's contents.  It does a postorder traversal instead of a
45           preorder traversal, working from the bottom of the directory tree
46           up where "find()" works from the top of the tree down.
47
48   %options
49       The first argument to "find()" is either a code reference to your
50       &wanted function, or a hash reference describing the operations to be
51       performed for each file.  The code reference is described in "The
52       wanted function" below.
53
54       Here are the possible keys for the hash:
55
56       "wanted"
57          The value should be a code reference.  This code reference is
58          described in "The wanted function" below. The &wanted subroutine is
59          mandatory.
60
61       "bydepth"
62          Reports the name of a directory only AFTER all its entries have been
63          reported.  Entry point "finddepth()" is a shortcut for specifying "{
64          bydepth => 1 }" in the first argument of "find()".
65
66       "preprocess"
67          The value should be a code reference. This code reference is used to
68          preprocess the current directory. The name of the currently
69          processed directory is in $File::Find::dir. Your preprocessing
70          function is called after "readdir()", but before the loop that calls
71          the "wanted()" function. It is called with a list of strings
72          (actually file/directory names) and is expected to return a list of
73          strings. The code can be used to sort the file/directory names
74          alphabetically, numerically, or to filter out directory entries
75          based on their name alone. When follow or follow_fast are in effect,
76          "preprocess" is a no-op.
77
78       "postprocess"
79          The value should be a code reference. It is invoked just before
80          leaving the currently processed directory. It is called in void
81          context with no arguments. The name of the current directory is in
82          $File::Find::dir. This hook is handy for summarizing a directory,
83          such as calculating its disk usage. When follow or follow_fast are
84          in effect, "postprocess" is a no-op.
85
86       "follow"
87          Causes symbolic links to be followed. Since directory trees with
88          symbolic links (followed) may contain files more than once and may
89          even have cycles, a hash has to be built up with an entry for each
90          file.  This might be expensive both in space and time for a large
91          directory tree. See "follow_fast" and "follow_skip" below.  If
92          either follow or follow_fast is in effect:
93
94          ·     It is guaranteed that an lstat has been called before the
95                user's "wanted()" function is called. This enables fast file
96                checks involving "_".  Note that this guarantee no longer
97                holds if follow or follow_fast are not set.
98
99          ·     There is a variable $File::Find::fullname which holds the
100                absolute pathname of the file with all symbolic links
101                resolved.  If the link is a dangling symbolic link, then
102                fullname will be set to "undef".
103
104          This is a no-op on Win32.
105
106       "follow_fast"
107          This is similar to follow except that it may report some files more
108          than once.  It does detect cycles, however.  Since only symbolic
109          links have to be hashed, this is much cheaper both in space and
110          time.  If processing a file more than once (by the user's "wanted()"
111          function) is worse than just taking time, the option follow should
112          be used.
113
114          This is also a no-op on Win32.
115
116       "follow_skip"
117          "follow_skip==1", which is the default, causes all files which are
118          neither directories nor symbolic links to be ignored if they are
119          about to be processed a second time. If a directory or a symbolic
120          link are about to be processed a second time, File::Find dies.
121
122          "follow_skip==0" causes File::Find to die if any file is about to be
123          processed a second time.
124
125          "follow_skip==2" causes File::Find to ignore any duplicate files and
126          directories but to proceed normally otherwise.
127
128       "dangling_symlinks"
129          Specifies what to do with symbolic links whose target doesn't exist.
130          If true and a code reference, will be called with the symbolic link
131          name and the directory it lives in as arguments.  Otherwise, if true
132          and warnings are on, a warning of the form "symbolic_link_name is a
133          dangling symbolic link\n" will be issued.  If false, the dangling
134          symbolic link will be silently ignored.
135
136       "no_chdir"
137          Does not "chdir()" to each directory as it recurses. The "wanted()"
138          function will need to be aware of this, of course. In this case, $_
139          will be the same as $File::Find::name.
140
141       "untaint"
142          If find is used in taint-mode (-T command line switch or if EUID !=
143          UID or if EGID != GID), then internally directory names have to be
144          untainted before they can be "chdir"'d to. Therefore they are
145          checked against a regular expression untaint_pattern.  Note that all
146          names passed to the user's "wanted()" function are still tainted. If
147          this option is used while not in taint-mode, "untaint" is a no-op.
148
149       "untaint_pattern"
150          See above. This should be set using the "qr" quoting operator.  The
151          default is set to "qr|^([-+@\w./]+)$|".  Note that the parentheses
152          are vital.
153
154       "untaint_skip"
155          If set, a directory which fails the untaint_pattern is skipped,
156          including all its sub-directories. The default is to "die" in such a
157          case.
158
159   The wanted function
160       The "wanted()" function does whatever verifications you want on each
161       file and directory.  Note that despite its name, the "wanted()"
162       function is a generic callback function, and does not tell File::Find
163       if a file is "wanted" or not.  In fact, its return value is ignored.
164
165       The wanted function takes no arguments but rather does its work through
166       a collection of variables.
167
168       $File::Find::dir is the current directory name,
169       $_ is the current filename within that directory
170       $File::Find::name is the complete pathname to the file.
171
172       The above variables have all been localized and may be changed without
173       affecting data outside of the wanted function.
174
175       For example, when examining the file /some/path/foo.ext you will have:
176
177           $File::Find::dir  = /some/path/
178           $_                = foo.ext
179           $File::Find::name = /some/path/foo.ext
180
181       You are chdir()'d to $File::Find::dir when the function is called,
182       unless "no_chdir" was specified. Note that when changing to directories
183       is in effect, the root directory (/) is a somewhat special case
184       inasmuch as the concatenation of $File::Find::dir, '/' and $_ is not
185       literally equal to $File::Find::name. The table below summarizes all
186       variants:
187
188                     $File::Find::name  $File::Find::dir  $_
189        default      /                  /                 .
190        no_chdir=>0  /etc               /                 etc
191                     /etc/x             /etc              x
192
193        no_chdir=>1  /                  /                 /
194                     /etc               /                 /etc
195                     /etc/x             /etc              /etc/x
196
197       When "follow" or "follow_fast" are in effect, there is also a
198       $File::Find::fullname.  The function may set $File::Find::prune to
199       prune the tree unless "bydepth" was specified.  Unless "follow" or
200       "follow_fast" is specified, for compatibility reasons (find.pl,
201       find2perl) there are in addition the following globals available:
202       $File::Find::topdir, $File::Find::topdev, $File::Find::topino,
203       $File::Find::topmode and $File::Find::topnlink.
204
205       This library is useful for the "find2perl" tool (distributed as part of
206       the App-find2perl CPAN distribution), which when fed,
207
208         find2perl / -name .nfs\* -mtime +7 \
209           -exec rm -f {} \; -o -fstype nfs -prune
210
211       produces something like:
212
213        sub wanted {
214           /^\.nfs.*\z/s &&
215           (($dev, $ino, $mode, $nlink, $uid, $gid) = lstat($_)) &&
216           int(-M _) > 7 &&
217           unlink($_)
218           ||
219           ($nlink || (($dev, $ino, $mode, $nlink, $uid, $gid) = lstat($_))) &&
220           $dev < 0 &&
221           ($File::Find::prune = 1);
222        }
223
224       Notice the "_" in the above "int(-M _)": the "_" is a magical
225       filehandle that caches the information from the preceding "stat()",
226       "lstat()", or filetest.
227
228       Here's another interesting wanted function.  It will find all symbolic
229       links that don't resolve:
230
231           sub wanted {
232                -l && !-e && print "bogus link: $File::Find::name\n";
233           }
234
235       Note that you may mix directories and (non-directory) files in the list
236       of directories to be searched by the "wanted()" function.
237
238           find(\&wanted, "./foo", "./bar", "./baz/epsilon");
239
240       In the example above, no file in ./baz/ other than ./baz/epsilon will
241       be evaluated by "wanted()".
242
243       See also the script "pfind" on CPAN for a nice application of this
244       module.
245

WARNINGS

247       If you run your program with the "-w" switch, or if you use the
248       "warnings" pragma, File::Find will report warnings for several weird
249       situations. You can disable these warnings by putting the statement
250
251           no warnings 'File::Find';
252
253       in the appropriate scope. See warnings for more info about lexical
254       warnings.
255

CAVEAT

257       $dont_use_nlink
258         You can set the variable $File::Find::dont_use_nlink to 0 if you are
259         sure the filesystem you are scanning reflects the number of
260         subdirectories in the parent directory's "nlink" count.
261
262         If you do set $File::Find::dont_use_nlink to 0, you may notice an
263         improvement in speed at the risk of not recursing into subdirectories
264         if a filesystem doesn't populate "nlink" as expected.
265
266         $File::Find::dont_use_nlink now defaults to 1 on all platforms.
267
268       symlinks
269         Be aware that the option to follow symbolic links can be dangerous.
270         Depending on the structure of the directory tree (including symbolic
271         links to directories) you might traverse a given (physical) directory
272         more than once (only if "follow_fast" is in effect).  Furthermore,
273         deleting or changing files in a symbolically linked directory might
274         cause very unpleasant surprises, since you delete or change files in
275         an unknown directory.
276

BUGS AND CAVEATS

278       Despite the name of the "finddepth()" function, both "find()" and
279       "finddepth()" perform a depth-first search of the directory hierarchy.
280

HISTORY

282       File::Find used to produce incorrect results if called recursively.
283       During the development of perl 5.8 this bug was fixed.  The first fixed
284       version of File::Find was 1.01.
285

SEE ALSO

287       find(1), find2perl.
288
289
290
291perl v5.30.1                      2019-11-29                   File::Find(3pm)
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