Re: Unix File Type with stat

I am wanting to see if my file is a link without having to rerun the stat operator. I saw an note in O'Reilly Perl book that stated that when returning info on a link, stat would return the filetype of the actual file (- , d, etc...). So maybe I should re-phrase my question to: Is there a way to have an algorithm that will tell me what type of file it is without having to check each specific bit. The following code returns a - for the file which is a link in both the $filelink and the $filetype variables.


# hard code a test link file to check
$source_file = "/temp/test/source/dir1/hello1_link.txt";

# define filetype array with potential first bits of mode
@ftypes  = qw(. p c ? d ? b ? - ? l ? s ? ? ?);
$ftypes0 = '';

# Get File Statistics Using Scalar context

($dev,$inode,$mode,$nlink,$uid,$gid,$rdev,$size,
 $atime,$mtime,$ctime,$blksize,$blocks) = stat($source_file);

$perms    = $mode & 07777;
$octperms = sprintf("%lo", $perms);
$filetype = $ftypes[($mode & 0170000)>>12];
$filelink = $ftypes[($mode & 0120000)>>12];
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And while I am admitting how much I don't know, what does the >>12 do in the array reference? Thanks.

Comment on Re: Unix File Type with stat Download Code

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Re: Re: Unix File Type with stat by Helter (Chaplain) on Sep 10, 2002 at 13:09 UTC
I can answer the last part about the bit shift operator. >> 12 takes the number to the left and shifts it 12 bits to the right. << 12 would shift it 12 bits to the left. In octal there are 3 bits per character shown (is this still called a nibble? Or is that only 4 bits, I don't play in octal that often :) So this will bitwise and $mode with 0170000 and then shift it down so that the bottom 4 zero's go away. 0170000 >> 12 = 017 Hope this helps!	[reply]
Re: Re: Unix File Type with stat by Zaxo (Archbishop) on Sep 10, 2002 at 15:57 UTC
You should use the lstat builtin if you don't want to resolve soft links. If you `use Fcntl qw(:mode);` you can get the constants by name. That will be easier to read and remember. ++Helter for the other answers. After Compline, Zaxo	[reply]