Ok, I'll bite
First of all, I don't see any need for oct(). This is a bitfield - so you might want to do a perl -e 'printf "0%o\n", 16895' for human consumption. And if you ever see that on Unix and it isn't called tmp, you'll probably also want to give the culprit a lecture about security risks. The readable form of this number is 040777, with 777 being the permission bits of read/write/executable for all of user, group and other (read maybe as 040ugo:) ).
Now let's peek at the includes, pretending that the 040 wasn't an obvious hint to us for the encoding of the directory file type.
Might be a useful trick of the trade for use with more difficult future questions in situations where Perl offers less or no suitable abstractions or you need some background to properly make use of them.
$ grep -lri mode_t /usr/include $ # as usual, do sceptically eyeball sys and linux, $ # but for now, this sounds like a hit: $ less /usr/include/bits/stat.h /* Encoding of the file mode. */ #define __S_IFMT 0170000 /* These bits determine file type. +*/ /* File types. */ #define __S_IFDIR 0040000 /* Directory. */ #define __S_IFCHR 0020000 /* Character device. */ #define __S_IFBLK 0060000 /* Block device. */ #define __S_IFREG 0100000 /* Regular file. */ #define __S_IFIFO 0010000 /* FIFO. */ #define __S_IFLNK 0120000 /* Symbolic link. */ #define __S_IFSOCK 0140000 /* Socket. */ /* POSIX.1b objects. Note that these macros always evaluate to zero. + But they do it by enforcing the correct use of the macros. */ #define __S_TYPEISMQ(buf) ((buf)->st_mode - (buf)->st_mode) #define __S_TYPEISSEM(buf) ((buf)->st_mode - (buf)->st_mode) #define __S_TYPEISSHM(buf) ((buf)->st_mode - (buf)->st_mode) /* Protection bits. */ #define __S_ISUID 04000 /* Set user ID on execution. */ #define __S_ISGID 02000 /* Set group ID on execution. */ #define __S_ISVTX 01000 /* Save swapped text after use (stick +y). */ #define __S_IREAD 0400 /* Read by owner. */ #define __S_IWRITE 0200 /* Write by owner. */ #define __S_IEXEC 0100 /* Execute by owner. */ # strange - this file doesn't define access macros for group/other..
The numbers above are octal numbers, for improved readability, as hinted at by the leading 0.
So you say in Perl $mode & 0777 to restrict the $mode to the actual file permissions (cf. chmod arguments!). Say $mode & 07 to check the access of nobody (but remember in the background that there's also filesystem specific stuff like ACL and Extended Attributes, which can modify the traditional perms; hopefully somebody alreade made a module for checking on these headaches :))
To test for a directory w/o POSIX, but just boolean operators directly. Which is just what the minimal wrapping by the POSIX module does:
warn "a dir\n" if (stat ".")[2] & 040000 == 040000with 040000 being __S_IFDIR from the includes above. Recognized POSIX::S_IFDIR?
I think that should be enough about background and boolean masking. Note that instead of and, or, exor you can also left or right-shift the bits (man perlop: search for &, |, ^, <<, >>).
AFAIS, the missing bits / misunderstandings were:
If possible however, try the normal perl tests like -d as already suggested.
cu
Peter
In reply to Re^2: POSIX::S_ISDIR() with $stat->mode values from Windows vs. Linux
by jakobi
in thread POSIX::S_ISDIR() with $stat->mode values from Windows vs. Linux
by isync
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