redhat man page for filetest

filetest(3pm)						 Perl Programmers Reference Guide					     filetest(3pm)

NAME
       filetest - Perl pragma to control the filetest permission operators

SYNOPSIS
	   $can_perhaps_read = -r "file";      # use the mode bits
	   {
	       use filetest 'access';	       # intuit harder
	       $can_really_read = -r "file";
	   }
	   $can_perhaps_read = -r "file";      # use the mode bits again

DESCRIPTION
       This pragma tells the compiler to change the behaviour of the filetest permissions operators, the "-r" "-w" "-x" "-R" "-W" "-X" (see perl-
       func).

       The default behaviour to use the mode bits as returned by the stat() family of calls.  This, however, may not be the right thing to do if
       for example various ACL (access control lists) schemes are in use.  For such environments, "use filetest" may help the permission operators
       to return results more consistent with other tools.

       Each "use filetest" or "no filetest" affects statements to the end of the enclosing block.

       There may be a slight performance decrease in the filetests when "use filetest" is in effect, because in some systems the extended func-
       tionality needs to be emulated.

       NOTE: using the file tests for security purposes is a lost cause from the start: there is a window open for race conditions (who is to say
       that the permissions will not change between the test and the real operation?).	Therefore if you are serious about security, just try the
       real operation and test for its success - think in terms of atomic operations.

       subpragma access

       Currently only one subpragma, "access" is implemented.  It enables (or disables) the use of access() or similar system calls.  This
       extended filetest functionality is used only when the argument of the operators is a filename, not when it is a filehandle.

perl v5.8.0							    2002-06-01							     filetest(3pm)