1package filetest; 2 3=head1 NAME 4 5filetest - Perl pragma to control the filetest permission operators 6 7=head1 SYNOPSIS 8 9 $can_perhaps_read = -r "file"; # use the mode bits 10 { 11 use filetest 'access'; # intuit harder 12 $can_really_read = -r "file"; 13 } 14 $can_perhaps_read = -r "file"; # use the mode bits again 15 16=head1 DESCRIPTION 17 18This pragma tells the compiler to change the behaviour of the filetest 19permissions operators, the C<-r> C<-w> C<-x> C<-R> C<-W> C<-X> 20(see L<perlfunc>). 21 22The default behaviour to use the mode bits as returned by the stat() 23family of calls. This, however, may not be the right thing to do if 24for example various ACL (access control lists) schemes are in use. 25For such environments, C<use filetest> may help the permission 26operators to return results more consistent with other tools. 27 28Each "use filetest" or "no filetest" affects statements to the end of 29the enclosing block. 30 31There may be a slight performance decrease in the filetests 32when C<use filetest> is in effect, because in some systems 33the extended functionality needs to be emulated. 34 35B<NOTE>: using the file tests for security purposes is a lost cause 36from the start: there is a window open for race conditions (who is to 37say that the permissions will not change between the test and the real 38operation?). Therefore if you are serious about security, just try 39the real operation and test for its success. Think atomicity. 40 41=head2 subpragma access 42 43Currently only one subpragma, C<access> is implemented. It enables 44(or disables) the use of access() or similar system calls. This 45extended filetest functionality is used only when the argument of the 46operators is a filename, not when it is a filehandle. 47 48=cut 49 50$filetest::hint_bits = 0x00400000; 51 52sub import { 53 if ( $_[1] eq 'access' ) { 54 $^H |= $filetest::hint_bits; 55 } else { 56 die "filetest: the only implemented subpragma is 'access'.\n"; 57 } 58} 59 60sub unimport { 61 if ( $_[1] eq 'access' ) { 62 $^H &= ~$filetest::hint_bits; 63 } else { 64 die "filetest: the only implemented subpragma is 'access'.\n"; 65 } 66} 67 681; 69