chmod(3pm)						User Contributed Perl Documentation						chmod(3pm)

NAME

       File::chmod - Implements symbolic and ls chmod modes

VERSION

       This is File::chmod v0.32.

SYNOPSIS

	 use File::chmod;

	 # chmod takes all three types
	 # these all do the same thing
	 chmod(0666,@files);
	 chmod("=rw",@files);
	 chmod("-rw-rw-rw-",@files);

	 # 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

DESCRIPTION

       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

	 chmod("o=,g-w","file1","file2");
	 # removes 'other' permissions, and the write bit for 'group'

	 chmod("=u","file1","file2");
	 # 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:

	 chmod("-rwxr-xr-x","file1","file2");
	 # the 0755 setting; user has read-write-execute, group and others
	 # have read-execute priveleges

	 chmod("-rwsrws---","file1","file2");
	 # 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.

   Functions
       Exported by default:

       chmod(MODE,FILES)
	   Takes an octal, symbolic, or "ls" mode, and then chmods each file appropriately.

       getchmod(MODE,FILES)
	   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:

       symchmod(MODE,FILES)
	   Takes a symbolic permissions mode, and chmods each file.

       lschmod(MODE,FILES)
	   Takes an "ls" permissions mode, and chmods each file.

       getsymchmod(MODE,FILES)
	   Returns a list of modified permissions, without chmodding files.  Accepts only symbolic permisson modes.

       getlschmod(MODE,FILES)
	   Returns a list of modified permissions, without chmodding files.  Accepts only "ls" permisson modes.

       getmod(FILES)
	   Returns a list of the current mode of each file.

   Variables
       $File::chmod::DEBUG
	   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.

       $File::chmod::MASK
	   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.

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

REVISIONS

       Note: this section was started with version 0.30.

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

   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/chmod.pm, 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

PORTING

       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"):

       Win32
	   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.

       MacOS
	   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.

AUTHOR

       Jeff "japhy" Pinyan, japhy.734+CPAN@gmail.com, CPAN ID: PINYAN

SEE ALSO

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

COPYRIGHT AND LICENCE

       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 v5.10.0							    2007-07-28								chmod(3pm)