1File::Find(3pm) Perl Programmers Reference Guide File::Find(3pm)
2
6 File::Find - Traverse a directory tree.
7
9 use File::Find;
10 find(\&wanted, @directories_to_search);
11 sub wanted { ... }
12 use File::Find;
14 finddepth(\&wanted, @directories_to_search);
15 sub wanted { ... }
16 use File::Find;
18 find({ wanted => \&process, follow => 1 }, '.');
19
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 find
27 find(\&wanted, @directories);
28 find(\%options, @directories);
29 "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 finddepth
39 finddepth(\&wanted, @directories);
40 finddepth(\%options, @directories);
41 "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 Despite the name of the "finddepth()" function, both "find()" and
49 "finddepth()" perform a depth-first search of the directory hierarchy.
50 %options
52 The first argument to "find()" is either a code reference to your
53 &wanted function, or a hash reference describing the operations to be
54 performed for each file. The code reference is described in "The
55 wanted function" below.
56 Here are the possible keys for the hash:
58 "wanted"
60 The value should be a code reference. This code reference is
61 described in "The wanted function" below. The &wanted subroutine is
62 mandatory.
63 "bydepth"
65 Reports the name of a directory only AFTER all its entries have
66 been reported. Entry point "finddepth()" is a shortcut for
67 specifying "{ bydepth => 1 }" in the first argument of "find()".
68 "preprocess"
70 The value should be a code reference. This code reference is used
71 to preprocess the current directory. The name of the currently
72 processed directory is in $File::Find::dir. Your preprocessing
73 function is called after "readdir()", but before the loop that
74 calls the "wanted()" function. It is called with a list of strings
75 (actually file/directory names) and is expected to return a list of
76 strings. The code can be used to sort the file/directory names
77 alphabetically, numerically, or to filter out directory entries
78 based on their name alone. When follow or follow_fast are in
79 effect, "preprocess" is a no-op.
80 "postprocess"
82 The value should be a code reference. It is invoked just before
83 leaving the currently processed directory. It is called in void
84 context with no arguments. The name of the current directory is in
85 $File::Find::dir. This hook is handy for summarizing a directory,
86 such as calculating its disk usage. When follow or follow_fast are
87 in effect, "postprocess" is a no-op.
88 "follow"
90 Causes symbolic links to be followed. Since directory trees with
91 symbolic links (followed) may contain files more than once and may
92 even have cycles, a hash has to be built up with an entry for each
93 file. This might be expensive both in space and time for a large
94 directory tree. See "follow_fast" and "follow_skip" below. If
95 either follow or follow_fast is in effect:
96 • It is guaranteed that an lstat has been called before the
98 user's "wanted()" function is called. This enables fast file
99 checks involving "_". Note that this guarantee no longer holds
100 if follow or follow_fast are not set.
101 • There is a variable $File::Find::fullname which holds the
103 absolute pathname of the file with all symbolic links resolved.
104 If the link is a dangling symbolic link, then fullname will be
105 set to "undef".
106 This is a no-op on Win32.
108 "follow_fast"
110 This is similar to follow except that it may report some files more
111 than once. It does detect cycles, however. Since only symbolic
112 links have to be hashed, this is much cheaper both in space and
113 time. If processing a file more than once (by the user's
114 "wanted()" function) is worse than just taking time, the option
115 follow should be used.
116 This is also a no-op on Win32.
118 "follow_skip"
120 "follow_skip==1", which is the default, causes all files which are
121 neither directories nor symbolic links to be ignored if they are
122 about to be processed a second time. If a directory or a symbolic
123 link are about to be processed a second time, File::Find dies.
124 "follow_skip==0" causes File::Find to die if any file is about to
126 be processed a second time.
127 "follow_skip==2" causes File::Find to ignore any duplicate files
129 and directories but to proceed normally otherwise.
130 "dangling_symlinks"
132 Specifies what to do with symbolic links whose target doesn't
133 exist. If true and a code reference, will be called with the
134 symbolic link name and the directory it lives in as arguments.
135 Otherwise, if true and warnings are on, a warning of the form
136 "symbolic_link_name is a dangling symbolic link\n" will be issued.
137 If false, the dangling symbolic link will be silently ignored.
138 "no_chdir"
140 Does not "chdir()" to each directory as it recurses. The "wanted()"
141 function will need to be aware of this, of course. In this case, $_
142 will be the same as $File::Find::name.
143 "untaint"
145 If find is used in taint-mode (-T command line switch or if EUID !=
146 UID or if EGID != GID), then internally directory names have to be
147 untainted before they can be "chdir"'d to. Therefore they are
148 checked against a regular expression untaint_pattern. Note that
149 all names passed to the user's "wanted()" function are still
150 tainted. If this option is used while not in taint-mode, "untaint"
151 is a no-op.
152 "untaint_pattern"
154 See above. This should be set using the "qr" quoting operator. The
155 default is set to "qr|^([-+@\w./]+)$|". Note that the parentheses
156 are vital.
157 "untaint_skip"
159 If set, a directory which fails the untaint_pattern is skipped,
160 including all its sub-directories. The default is to "die" in such
161 a case.
162 The wanted function
164 The "wanted()" function does whatever verifications you want on each
165 file and directory. Note that despite its name, the "wanted()"
166 function is a generic callback function, and does not tell File::Find
167 if a file is "wanted" or not. In fact, its return value is ignored.
168 The wanted function takes no arguments but rather does its work through
170 a collection of variables.
171 $File::Find::dir is the current directory name,
173 $_ is the current filename within that directory
174 $File::Find::name is the complete pathname to the file.
175 The above variables have all been localized and may be changed without
177 affecting data outside of the wanted function.
178 For example, when examining the file /some/path/foo.ext you will have:
180 $File::Find::dir = /some/path/
182 $_ = foo.ext
183 $File::Find::name = /some/path/foo.ext
184 You are chdir()'d to $File::Find::dir when the function is called,
186 unless "no_chdir" was specified. Note that when changing to directories
187 is in effect, the root directory (/) is a somewhat special case
188 inasmuch as the concatenation of $File::Find::dir, '/' and $_ is not
189 literally equal to $File::Find::name. The table below summarizes all
190 variants:
191 $File::Find::name $File::Find::dir $_
193 default / / .
194 no_chdir=>0 /etc / etc
195 /etc/x /etc x
196 no_chdir=>1 / / /
198 /etc / /etc
199 /etc/x /etc /etc/x
200 When "follow" or "follow_fast" are in effect, there is also a
202 $File::Find::fullname. The function may set $File::Find::prune to
203 prune the tree unless "bydepth" was specified. Unless "follow" or
204 "follow_fast" is specified, for compatibility reasons (find.pl,
205 find2perl) there are in addition the following globals available:
206 $File::Find::topdir, $File::Find::topdev, $File::Find::topino,
207 $File::Find::topmode and $File::Find::topnlink.
208 This library is useful for the "find2perl" tool (distributed as part of
210 the App-find2perl CPAN distribution), which when fed,
211 find2perl / -name .nfs\* -mtime +7 \
213 -exec rm -f {} \; -o -fstype nfs -prune
214 produces something like:
216 sub wanted {
218 /^\.nfs.*\z/s &&
219 (($dev, $ino, $mode, $nlink, $uid, $gid) = lstat($_)) &&
220 int(-M _) > 7 &&
221 unlink($_)
222 ||
223 ($nlink || (($dev, $ino, $mode, $nlink, $uid, $gid) = lstat($_))) &&
224 $dev < 0 &&
225 ($File::Find::prune = 1);
226 }
227 Notice the "_" in the above "int(-M _)": the "_" is a magical
229 filehandle that caches the information from the preceding "stat()",
230 "lstat()", or filetest.
231 Here's another interesting wanted function. It will find all symbolic
233 links that don't resolve:
234 sub wanted {
236 -l && !-e && print "bogus link: $File::Find::name\n";
237 }
238 Note that you may mix directories and (non-directory) files in the list
240 of directories to be searched by the "wanted()" function.
241 find(\&wanted, "./foo", "./bar", "./baz/epsilon");
243 In the example above, no file in ./baz/ other than ./baz/epsilon will
245 be evaluated by "wanted()".
246 See also the script "pfind" on CPAN for a nice application of this
248 module.
249
251 If you run your program with the "-w" switch, or if you use the
252 "warnings" pragma, File::Find will report warnings for several weird
253 situations. You can disable these warnings by putting the statement
254 no warnings 'File::Find';
256 in the appropriate scope. See warnings for more info about lexical
258 warnings.
259
261 $dont_use_nlink
262 You can set the variable $File::Find::dont_use_nlink to 0 if you
263 are sure the filesystem you are scanning reflects the number of
264 subdirectories in the parent directory's "nlink" count.
265 If you do set $File::Find::dont_use_nlink to 0, you may notice an
267 improvement in speed at the risk of not recursing into
268 subdirectories if a filesystem doesn't populate "nlink" as
269 expected.
270 $File::Find::dont_use_nlink now defaults to 1 on all platforms.
272 symlinks
274 Be aware that the option to follow symbolic links can be dangerous.
275 Depending on the structure of the directory tree (including
276 symbolic links to directories) you might traverse a given
277 (physical) directory more than once (only if "follow_fast" is in
278 effect). Furthermore, deleting or changing files in a symbolically
279 linked directory might cause very unpleasant surprises, since you
280 delete or change files in an unknown directory.
281
283 File::Find used to produce incorrect results if called recursively.
284 During the development of perl 5.8 this bug was fixed. The first fixed
285 version of File::Find was 1.01.
286
288 find(1), find2perl.
289perl v5.34.1 2022-03-15 File::Find(3pm)