 |
Index for
Section 3 |
|
 |
Alphabetical
listing for F |
|
 |
Bottom of
page |
|
File::Find(3)
NAME
File::Find - Traverse a directory tree.
SYNOPSIS
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 }, '.');
DESCRIPTION
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
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
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 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.
"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 _.
* 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, 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.
"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
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
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 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";
}
See also the script "pfind" on CPAN for a nice application of this module.
WARNINGS
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 perllexwarn for more info about lexical
warnings.
CAVEAT
$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 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.
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.
NOTES
· 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 relative 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 pathname
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 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 creator 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.
BUGS AND CAVEATS
Despite the name of the "finddepth()" function, both "find()" and
"finddepth()" perform a depth-first search of the directory hierarchy.
HISTORY
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.
|
Index for
Section 3 |
|
|
Alphabetical
listing for F |
|
 |
Top of
page |
|