1package filetest; 2 3our $VERSION = '1.00'; 4 5=head1 NAME 6 7filetest - Perl pragma to control the filetest permission operators 8 9=head1 SYNOPSIS 10 11 $can_perhaps_read = -r "file"; # use the mode bits 12 { 13 use filetest 'access'; # intuit harder 14 $can_really_read = -r "file"; 15 } 16 $can_perhaps_read = -r "file"; # use the mode bits again 17 18=head1 DESCRIPTION 19 20This pragma tells the compiler to change the behaviour of the filetest 21permissions operators, the C<-r> C<-w> C<-x> C<-R> C<-W> C<-X> 22(see L<perlfunc>). 23 24The default behaviour to use the mode bits as returned by the stat() 25family of calls. This, however, may not be the right thing to do if 26for example various ACL (access control lists) schemes are in use. 27For such environments, C<use filetest> may help the permission 28operators to return results more consistent with other tools. 29 30Each "use filetest" or "no filetest" affects statements to the end of 31the enclosing block. 32 33There may be a slight performance decrease in the filetests 34when C<use filetest> is in effect, because in some systems 35the extended functionality needs to be emulated. 36 37B<NOTE>: using the file tests for security purposes is a lost cause 38from the start: there is a window open for race conditions (who is to 39say that the permissions will not change between the test and the real 40operation?). Therefore if you are serious about security, just try 41the real operation and test for its success. Think atomicity. 42 43=head2 subpragma access 44 45Currently only one subpragma, C<access> is implemented. It enables 46(or disables) the use of access() or similar system calls. This 47extended filetest functionality is used only when the argument of the 48operators is a filename, not when it is a filehandle. 49 50=cut 51 52$filetest::hint_bits = 0x00400000; 53 54sub import { 55 if ( $_[1] eq 'access' ) { 56 $^H |= $filetest::hint_bits; 57 } else { 58 die "filetest: the only implemented subpragma is 'access'.\n"; 59 } 60} 61 62sub unimport { 63 if ( $_[1] eq 'access' ) { 64 $^H &= ~$filetest::hint_bits; 65 } else { 66 die "filetest: the only implemented subpragma is 'access'.\n"; 67 } 68} 69 701; 71