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 command. File::Find
exports two functions, find
and finddepth
. They work similarly
but have subtle differences.
- 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(\&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.
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 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:
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";
- }
Note that you may mix directories and (non-directory) files in the list of
directories to be searched by the wanted()
function.
- find(\&wanted, "./foo", "./bar", "./baz/epsilon");
In the example above, no file in ./baz/ other than ./baz/epsilon will be
evaluated by wanted()
.
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';
in the appropriate scope. See warnings for more info about lexical warnings.
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.
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.
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 recursively. During the development of perl 5.8 this bug was fixed. The first fixed version of File::Find was 1.01.
find, find2perl.