Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
chmod(3)	      User Contributed Perl Documentation	      chmod(3)

       File::chmod - Implements	symbolic and ls	chmod modes

       This is File::chmod v0.32.

	 use File::chmod;

	 # chmod takes all three types
	 # these all do	the same thing

	 # or

	 use File::chmod qw( symchmod lschmod );

	 chmod(0666,@files);	       # this is the normal chmod
	 symchmod("=rw",@files);       # takes symbolic	modes only
	 lschmod("-rw-rw-rw-",@files); # takes "ls" modes only

	 # more	functions, read	on to understand

       File::chmod is a	utility	that allows you	to bypass system calls or bit
       processing of a file's permissions.  It overloads the chmod() function
       with its	own that gets an octal mode, a symbolic	mode (see below), or
       an "ls" mode (see below).  If you wish not to overload chmod(), you can
       export symchmod() and lschmod(),	which take, respectively, a symbolic
       mode and	an "ls"	mode.

       Symbolic	modes are thoroughly described in your chmod(1)	man page, but
       here are	a few examples.

	 # NEW:	if $UMASK is true, symchmod() applies a	bit-mask found in $MASK

	 chmod("+x","file1","file2");  # overloaded chmod(), that is...
	 # turns on the	execute	bit for	all users on those two files

	 # removes 'other' permissions,	and the	write bit for 'group'

	 # sets	all bits to those in 'user'

       "ls" modes are the type produced	on the left-hand side of an "ls	-l" on
       a directory.  Examples are:

	 # the 0755 setting; user has read-write-execute, group	and others
	 # have	read-execute priveleges

	 # sets	read-write-execute for user and	group, none for	others
	 # also	sets set-uid and set-gid bits

       The regular chmod() and lschmod() are absolute; that is,	they are not
       appending to or subtracting from	the current file mode.	They set it,
       regardless of what it had been before.  symchmod() is useful for
       allowing	the modifying of a file's permissions without having to	run a
       system call or determining the file's permissions, and then combining
       that with whatever bits are appropriate.	 It also operates separately
       on each file.

       An added	feature	to version 0.30	is the $UMASK variable,	explained
       below; if symchmod() is called and this variable	is true, then the
       function	uses the (also new) $MASK variable (which defaults to umask())
       as a mask against the new mode.	This is	documented below more clearly.

       Exported	by default:

	   Takes an octal, symbolic, or	"ls" mode, and then chmods each	file

	   Returns a list of modified permissions, without chmodding files.
	   Accepts any of the three kinds of modes.

	     @newmodes = getchmod("+x","file1","file2");
	     # @newmodes holds the octal permissons of the files'
	     # modes, if they were to be sent through chmod("+x"...)

       Exported	by request:

	   Takes a symbolic permissions	mode, and chmods each file.

	   Takes an "ls" permissions mode, and chmods each file.

	   Returns a list of modified permissions, without chmodding files.
	   Accepts only	symbolic permisson modes.

	   Returns a list of modified permissions, without chmodding files.
	   Accepts only	"ls" permisson modes.

	   Returns a list of the current mode of each file.

	   If set to a true value, it will report warnings, similar to those
	   produced by chmod() on your system.	Otherwise, the functions will
	   not report errors.  Example:	a file can not have file-locking and
	   the set-gid bits on at the same time.  If $File::chmod::DEBUG is
	   true, the function will report an error.  If	not, you are not
	   warned of the conflict.  It is set to 1 as default.

	   Contains the	umask to apply to new file modes when using
	   getsymchmod().  This	defaults to the	return value of	umask()	at
	   compile time.  Is only applied if $UMASK is true.

	   This	is a boolean which tells getsymchmod() whether or not to apply
	   the umask found in $MASK.  It defaults to true.

       Note: this section was started with version 0.30.

       This is an in-depth look	at the changes being made from version to

   0.31	to 0.32
       license added
	   I added a license to	this module so that it can be used places
	   without asking my permission.  Sorry, Adam.

   0.30	to 0.31
       fixed getsymchmod() bug
	   Whoa.  getsymchmod()	was doing some crazy ish.  That's about	all I
	   can say.  I did a great deal	of debugging, and fixed	it up.	It ALL
	   had to do with two things:

	     $or = (/+=/ ? 1 : 0); # should have been /[+=]/

	     /u/ && $ok	? u_or() : u_not(); # should have been /u/ and $ok

       fixed getmod() bug
	   I was using map() incorrectly in getmod().  Fixed that.

       condensed lschmod()
	   I shorted it	up, getting rid	a variable.

   0.21	to 0.30
       added umask() honoring for symchmod()
	   The symchmod() function now honors the $UMASK and $MASK variables.
	   $UMASK is a boolean which indicates whether or not to honor the
	   $MASK variable.  $MASK holds	a umask, and it	defaults to umask().
	   $UMASK defaults to true.  These variables are NOT exported.	They
	   must	explictly set (i.e. $File::chmod::UMASK	= 0).

       function	name changes
	   Renamed internal function determine_mode() to mode().  However, if
	   you happen to be using determine_mode() somewhere, mode() will be
	   called, but you'll also get a warning about deprecation.

	   Renamed internal functions {or,not}_{l,s,t} to {l,s,t}_{or,not}.
	   This	is to keep in standard with the	OTHER 6	pairs of bitwise
	   functions, such as r_or() and g_not().  I don't know	WHY the	others
	   had 'not' or	'or' in	the front.

       fixed debugging bugs
	   Certain calls to warn() were	not guarded by the $DEBUG variable,
	   and now they	are.  Also, for	some reason, I left a debugging	check
	   (that didn't	check to see if	$DEBUG was true) in getsymchmod(),
	   line	118.  It printed "ENTERING /g/".  It's gone now.

       fixed set-uid and set-gid bug
	   Heh,	it seems that in the previous version of File::chmod, the
	   following code went along broken:

	     # or_s sub, File/,	v0.21, line 330
	     ($VAL & 00100) && do {
	       $DEBUG && warn("execute bit must	be on for set-uid"); 1;
	     } && next;

	   Aside from me using '&&' more than enough (changed in the new
	   code), this is broken.  This	is now fixed.

       fixed file lock/set-gid bug
	   The not_l() function	(now renamed to	l_not()) used to take the file
	   mode	and bit-wise NOT it with ~02000.  However, it did not check if
	   the file was	locked vs. set-gid.  Now, the function is "$VAL	&=
	   ~02000 if not $VAL &	00010;".

       removed useless data structures
	   I do	not know why I had the $S variable, or %r, %w, and %x hashes.
	   In fact, $S was declared in "use vars qw( ... );", but never	given
	   a value, and	the %r,	%w, and	%x hashes had a	'full' key which never
	   got used.  And the hashes themselves	weren't	really needed anyway.
	   Here	is a list of the variables no longer in	use, and what they
	   have	been replaced with (if any):

	     $S		   nothing
	     $U, $G, $O	   $W
	     %r, %w, %x	   octal numbers
	     @files	   @_ (I had @files = @_; in nearly EVERY sub)
	     $c		   $_

       compacted code
	   The first version of	File::chmod that was published was 0.13, and
	   it was written in approximately 10 days, being given	the off-and-on
	   treatment I end up having to	give several projects, due to more
	   pressing matters.  Well, since then,	most of	the code has stayed
	   the same, although bugs were	worked out.  Well, I got rid of	a lot
	   of slow, clunky, and	redundant sections of code in this version.
	   Sections include the	processing of each character of	the mode in
	   getsymchmod(), the getmod() subroutine, um, nearly ALL of the
	   getsymchmod() function, now that I look at it.

	   Here's part of the getsymchmod() rewrite:

	     for ($c){
	       if (/u/){
		 u_or()	if $MODE eq "+"	or $MODE eq "=";
		 u_not() if $MODE eq "-";

	     # changed to

	     /u/ && $or	? u_or() : u_and();
	     # note: operating on $_, $c isn't used anymore
	     # note: $or holds 1 if the	$MODE was + or =, 0 if $MODE was -
	     # note: previous was redundant.  didn't need $MODE	eq "-" check
	     #	     because u_or() and	u_not()	both go	to the next character

       This is only good on Unix-like boxes.  I	would like people to help me
       work on File::chmod for any OS that deserves it.	 If you	would like to
       help, please email me (address below) with the OS and any information
       you might have on how chmod() should work on it;	if you don't have any
       specific	information, but would still like to help, hey,	that's good
       too.  I have the	following information (from "perlport"):

	   Only	good for changing "owner" read-write access, "group", and
	   "other" bits	are meaningless.  NOTE:	Win32::File and
	   Win32::FileSecurity already do this.	 I do not currently see	a need
	   to port File::chmod.

	   Only	limited	meaning. Disabling/enabling write permission is	mapped
	   to locking/unlocking	the file.

       RISC OS
	   Only	good for changing "owner" and "other" read-write access.

       Jeff "japhy" Pinyan,, CPAN ID: PINYAN

	 Stat::lsMode (by Mark-James Dominus, CPAN ID: MJD)
	 chmod(1) manpage
	 perldoc -f chmod
	 perldoc -f stat

       Copyright (C) 2007 by Jeff Pinyan

       This library is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself, either Perl	version	5.8.8 or, at
       your option, any	later version of Perl 5	you may	have available.

perl v5.32.0			  2007-07-28			      chmod(3)


Want to link to this manual page? Use this URL:

home | help