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5ff3f7a4 GS |
1 | package filetest; |
2 | ||
b75c8c73 MS |
3 | our $VERSION = '1.00'; |
4 | ||
5ff3f7a4 GS |
5 | =head1 NAME |
6 | ||
7 | filetest - Perl pragma to control the filetest permission operators | |
8 | ||
9 | =head1 SYNOPSIS | |
3cb6de81 | 10 | |
5ff3f7a4 GS |
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 | ||
20 | This pragma tells the compiler to change the behaviour of the filetest | |
80d06f2d JH |
21 | permissions operators, the C<-r> C<-w> C<-x> C<-R> C<-W> C<-X> |
22 | (see L<perlfunc>). | |
5ff3f7a4 GS |
23 | |
24 | The default behaviour to use the mode bits as returned by the stat() | |
25 | family of calls. This, however, may not be the right thing to do if | |
26 | for example various ACL (access control lists) schemes are in use. | |
27 | For such environments, C<use filetest> may help the permission | |
28 | operators to return results more consistent with other tools. | |
29 | ||
30 | Each "use filetest" or "no filetest" affects statements to the end of | |
31 | the enclosing block. | |
32 | ||
33 | There may be a slight performance decrease in the filetests | |
34 | when C<use filetest> is in effect, because in some systems | |
35 | the extended functionality needs to be emulated. | |
36 | ||
6ca796d8 | 37 | B<NOTE>: using the file tests for security purposes is a lost cause |
80d06f2d JH |
38 | from the start: there is a window open for race conditions (who is to |
39 | say that the permissions will not change between the test and the real | |
40 | operation?). Therefore if you are serious about security, just try | |
41 | the real operation and test for its success. Think atomicity. | |
5ff3f7a4 GS |
42 | |
43 | =head2 subpragma access | |
44 | ||
45 | Currently only one subpragma, C<access> is implemented. It enables | |
46 | (or disables) the use of access() or similar system calls. This | |
47 | extended filetest functionality is used only when the argument of the | |
48 | operators is a filename, not when it is a filehandle. | |
49 | ||
50 | =cut | |
51 | ||
d5448623 GS |
52 | $filetest::hint_bits = 0x00400000; |
53 | ||
5ff3f7a4 GS |
54 | sub import { |
55 | if ( $_[1] eq 'access' ) { | |
d5448623 | 56 | $^H |= $filetest::hint_bits; |
5ff3f7a4 GS |
57 | } else { |
58 | die "filetest: the only implemented subpragma is 'access'.\n"; | |
59 | } | |
60 | } | |
61 | ||
62 | sub unimport { | |
63 | if ( $_[1] eq 'access' ) { | |
d5448623 | 64 | $^H &= ~$filetest::hint_bits; |
5ff3f7a4 GS |
65 | } else { |
66 | die "filetest: the only implemented subpragma is 'access'.\n"; | |
67 | } | |
68 | } | |
69 | ||
70 | 1; |