chmod in perl script

mcleary has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks,

I need to find the perl equivalent to this unix/linux (yes we are supporting both) command:

chmod g+s directory

Would I just be able to add the same thing to my script without using a system command or is there something else I need? I can't find any perl examples using g+s.

Thanks, Michele

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Re: chmod in perl script by bellaire (Hermit) on Feb 04, 2011 at 14:37 UTC
You do use chmod, but you have to keep in mind that unlike the command-line `chmod`, which can simply flip bits on or off, perl's `chmod` sets the entire permission set as a single unit. Basically, you have to read the current permissions off the file using stat, add group sticky to those permissions bitwise, and then apply the new permissions using `chmod`. I think the group sticky bit is `02000`, so that'd be: `my $filename = 'filename'; my $perms = ((stat($filename))[2] & 07777); # Just permissions, not + type my $newperms = $perms ^ 02000; # Add the group sticky +bit chmod $newperms, $filename or die "Could not change permissions: $!";` [download]	[reply] [d/l] [select]
Re^2: chmod in perl script by mcleary (Initiate) on Feb 08, 2011 at 19:09 UTC
Thanks a lot Monks! I wound up using bellaire's suggestion and it worked perfectly. Take care, Michele	[reply]
Re: chmod in perl script by marto (Cardinal) on Feb 04, 2011 at 13:38 UTC
See chmod.	[reply]
Re: chmod in perl script by Corion (Patriarch) on Feb 04, 2011 at 13:38 UTC
Have you looked at chmod? Finding out the numeric values for `g+s` is likely easiest done by using `ls` on such a directory and then looking at the numeric value for the permissions. Likely it's `04000` for setting the group-sticky-bit, but I don't know.	[reply] [d/l] [select]
Re: chmod in perl script by ambrus (Abbot) on Feb 05, 2011 at 08:40 UTC
I think we've answered this in the chatterbox. My suggestion was `my @s = lstat $dirname or die "stat $!"; -l _ and die "islink $!"; chmod+($s[2] \| 02000), $dirname or die "chmod";` [download] If you prefer symbolic constants, you can `use Fcntl "S_ISGID";` and then write `S_ISGID()` instead of `02000`. You could also try the File::chmod module to use symbolic mode letters.	[reply] [d/l] [select]