filetest(3) Perl Programmers Reference Guide filetest(3)NAMEfiletest - 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 the perlfunc manpage).
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 con
trol 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 functionality needs to be emu
lated.
NOTE: using the file tests for security purposes is a lost
cause from the start: there is a window open for race con
ditions (who is to say that the permissions will not
change between the test and the real operation?). There
fore if you are serious about security, just try the real
operation and test for its success. Think atomicity.
subpragma access
Currently only one subpragma, "access" is implemented. It
enables (or disables) the use of access() or similar sys
tem calls. This extended filetest functionality is used
only when the argument of the operators is a filename, not
when it is a filehandle.
2001-02-22 perl v5.6.1 filetest(3)
