File::Find(3) Perl Programmers Reference Guide File::Find(3)NAME
find - traverse a file tree
finddepth - traverse a directory structure depth-first
SYNOPSIS
use File::Find;
find(\&wanted, '/foo', '/bar');
sub wanted { ... }
use File::Find;
finddepth(\&wanted, '/foo', '/bar');
sub wanted { ... }
use File::Find;
find({ wanted => \&process, follow => 1 }, '.');
DESCRIPTION
The first argument to find() is either a hash reference
describing the operations to be performed for each file,
or a code reference.
Here are the possible keys for the hash:
""wanted""
The value should be a code reference. This code refer
ence is called 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 refer
ence is used to preprocess a directory; it is called
after readdir() but before the loop that calls the
wanted() function. It is called with a list of strings
and is expected to return a list of strings. The code
can be used to sort the strings alphabetically, numeri
cally, or to filter out directory entries based on
their name alone.
""postprocess""
The value should be a code reference. It is invoked
just before leaving the current directory. It is
called in void context with no arguments. The name of
the current directory is in $File::Find::dir. This
hook is handy for summarizing a directory, such as cal
culating its disk usage.
""follow""
Causes symbolic links to be followed. Since directory
trees with symbolic links (followed) may contain files
more than once and may even have cycles, a hash has to
be built up with an entry for each file. This might be
expensive both in space and time for a large directory
tree. See follow_fast and follow_skip below. If either
follow or follow_fast is in effect:
It is guaranteed that an lstat has been called
before the user's wanted() function is called.
This enables fast file checks involving _.
There is a variable "$File::Find::fullname" which
holds the absolute pathname of the file with all
symbolic links resolved
""follow_fast""
This is similar to follow except that it may report
some files more than once. It does detect cycles, how
ever. Since only symbolic links have to be hashed,
this is much cheaper both in space and time. If pro
cessing a file more than once (by the user's wanted()
function) is worse than just taking time, the option
follow should be used.
""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 sec
ond time. If a directory or a symbolic link are about
to be processed a second time, File::Find dies. "fol
low_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
dirctories but to proceed normally otherwise.
""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
cd'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.
""untaint_pattern""
See above. This should be set using the "qr" quoting
operator. The default is set to "qr|^([-+@\w./]+)$|".
Note that the parantheses are vital.
""untaint_skip""
If set, directories (subtrees) which fail the
untaint_pattern are skipped. The default is to 'die' in
such a case.
The wanted() function does whatever verifications you
want. "$File::Find::dir" contains the current directory
name, and "$_" the current filename within that directory.
"$File::Find::name" contains the complete pathname to the
file. You are chdir()'d to "$File::Find::dir" when the
function is called, unless "no_chdir" was specified. When
<follow> or <follow_fast> are in effect, there is also a
"$File::Find::fullname". The function may set
"$File::Find::prune" to prune the tree unless "bydepth"
was specified. Unless "follow" or "follow_fast" is speci
fied, for compatibility reasons (find.pl, find2perl) there
are in addition the following globals available:
"$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);
}
Set the variable "$File::Find::dont_use_nlink" if you're
using AFS, since AFS cheats.
Here's another interesting wanted function. It will find
all symlinks 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.
CAVEAT
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.
2001-03-03 perl v5.6.1 File::Find(3)
