{
    "mode": "perldoc",
    "parameter": "filetest",
    "section": "",
    "url": "https://www.chedong.com/phpMan.php/perldoc/filetest/json",
    "generated": "2026-06-15T14:37:54Z",
    "synopsis": "$canperhapsread = -r \"file\";      # use the mode bits\n{\nuse filetest 'access';          # intuit harder\n$canreallyread = -r \"file\";\n}\n$canperhapsread = -r \"file\";      # use the mode bits again",
    "sections": {
        "NAME": {
            "content": "filetest - Perl pragma to control the filetest permission operators\n",
            "subsections": []
        },
        "SYNOPSIS": {
            "content": "$canperhapsread = -r \"file\";      # use the mode bits\n{\nuse filetest 'access';          # intuit harder\n$canreallyread = -r \"file\";\n}\n$canperhapsread = -r \"file\";      # use the mode bits again\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "This pragma tells the compiler to change the behaviour of the filetest permission operators,\n\"-r\" \"-w\" \"-x\" \"-R\" \"-W\" \"-X\" (see perlfunc).\n\nThe default behaviour of file test operators is to use the simple mode bits as returned by the",
            "subsections": [
                {
                    "name": "stat",
                    "content": "define more complex access rights, for example ACLs (Access Control Lists). For such\nenvironments, \"use filetest\" may help the permission operators to return results more consistent\nwith other tools.\n\nThe \"use filetest\" or \"no filetest\" statements affect file tests defined in their block, up to\nthe end of the closest enclosing block (they are lexically block-scoped).\n\nCurrently, only the \"access\" sub-pragma is implemented. It enables (or disables) the use of"
                },
                {
                    "name": "access",
                    "content": "below.\n"
                },
                {
                    "name": "Consider this carefully",
                    "content": "The stat() mode bits are probably right for most of the files and directories found on your\nsystem, because few people want to use the additional features offered by access(). But you may\nencounter surprises if your program runs on a system that uses ACLs, since the stat()\ninformation won't reflect the actual permissions.\n\nThere may be a slight performance decrease in the filetest operations when the filetest pragma\nis in effect, because checking bits is very cheap.\n\nAlso, note that using the file tests for security purposes is a lost cause from the start: there\nis a window open for race conditions (who is to say that the permissions will not change between\nthe test and the real operation?). Therefore if you are serious about security, just try the\nreal operation and test for its success - think in terms of atomic operations. Filetests are\nmore useful for filesystem administrative tasks, when you have no need for the content of the\nelements on disk.\n\nThe \"access\" sub-pragma\nUNIX and POSIX systems provide an abstract access() operating system call, which should be used\nto query the read, write, and execute rights. This function hides various distinct approaches in\nadditional operating system specific security features, like Access Control Lists (ACLs)\n\nThe extended filetest functionality is used by Perl only when the argument of the operators is a\nfilename, not when it is a filehandle.\n\nLimitation with regard to \"\"\nBecause access() does not invoke stat() (at least not in a way visible to Perl), the stat result\ncache \"\" is not set. This means that the outcome of the following two tests is different. The\nfirst has the stat bits of /etc/passwd in \"\", and in the second case this still contains the\nbits of \"/etc\".\n\n{ -d '/etc';\n-w '/etc/passwd';\nprint -f  ? 'Yes' : 'No';   # Yes\n}\n\n{ use filetest 'access';\n-d '/etc';\n-w '/etc/passwd';\nprint -f  ? 'Yes' : 'No';   # No\n}\n\nOf course, unless your OS does not implement access(), in which case the pragma is simply\nignored. Best not to use \"\" at all in a file where the filetest pragma is active!\n\nAs a side effect, as \"\" doesn't work, stacked filetest operators (\"-f -w $file\") won't work\neither.\n\nThis limitation might be removed in a future version of perl.\n"
                }
            ]
        }
    },
    "summary": "filetest - Perl pragma to control the filetest permission operators",
    "flags": [],
    "examples": [],
    "see_also": []
}