File::Find(3p) Perl Programmers Reference Guide File::Find(3p)
File::Find - Traverse a directory tree.
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 }, '.');
These are functions for searching through directory trees
doing work on each file found similar to the Unix find com-
mand. 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 subroutine.
(See below for details on how to use the &wanted func-
tion). Additionally, for each directory found, it will
"chdir()" into that directory and continue the search,
invoking the &wanted function on each file or subdirec-
tory 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 refer-
ence is described in "The wanted function" below.
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Here are the possible keys for the hash:
"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 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
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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 pro-
cessed 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 other-
wise.
"dangling_symlinks"
If true and a code reference, will be called with the
symbolic link name and the directory it lives in as argu-
ments. 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
$File::Find::name.
"untaint"
If find is used in taint-mode (-T command line switch or
if EUID != UID or if EGID != GID) then internally direc-
tory names have to be untainted before they can be
chdir'ed to. Therefore they are checked against a regular
expression untaint_pattern. Note that all names passed
to the user's wanted() function are still tainted. If
this option is used while not in taint-mode, "untaint" is
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a no-op.
"untaint_pattern"
See above. This should be set using the "qr" quoting
operator. The default is set to "qr|^([-+@\w./]+)$|".
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 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
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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 magi-
cal filehandle that caches the information from the preced-
ing "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.
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';
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in the appropriate scope. See perllexwarn for more info
about lexical warnings.
$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 filesystems that do not have an
"nlink" count matching the number of sub-directories.
Examples are ISO-9660 (CD-ROM), AFS, HPFS (OS/2 filesys-
tem), FAT (DOS file system) and a couple of others.
You shouldn't need to set this variable, since File::Find
should now detect such filesystems on-the-fly and switch
itself to using stat. This works even for parts of your
filesystem, 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.
+ 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 rela-
tive 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 path-
name to that directory, and $File::Find::fullname,
which holds the absolute pathname of that directory
with all symbolic links resolved, may or may not end
with a ':'.
+ The default "untaint_pattern" (see above) on Mac OS
is set to "qr|^(.+)$|". Note that the parentheses
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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 crea-
tor 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"
desktop, each disk volume actually maintains its own
"Desktop Folder" directory.
Despite the name of the "finddepth()" function, both
"find()" and "finddepth()" perform a depth-first search of
the directory hierarchy.
File::Find used to produce incorrect results if called
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recursively. During the development of perl 5.8 this bug was
fixed. The first fixed version of File::Find was 1.01.
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