How to use chmod u +x in perl

fearthechris29 has asked for the wisdom of the Perl Monks concerning the following question:

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Re: How to use chmod u +x in perl by hdb (Monsignor) on Nov 25, 2013 at 08:34 UTC
From the documentation of the Perl command chmod: The first element of the list must be the numeric mode, which should probably be an octal number, and which definitely should not be a string of octal digits: 0644 is okay, but "0644" is not. No mention of being able to specify "u+x" or the like. Also, having not used Unix for a while, what is the reason to mark a pdf file as executable?	[reply]
Re^2: How to use chmod u +x in perl by taint (Chaplain) on Nov 25, 2013 at 14:31 UTC
"what is the reason to mark a pdf file as executable?" Good question. Perhaps it carries a PAYLOAD (TROJAN). ;) ;) Seriously. To the OP; There's precious little reason to add the x bit to a document. In fact, it could potentially cause you grief. If exposed to the wild (it's within your web space, or those other than yourself have access), it could be used in malicious ways. Perhaps you would find one of the following perms more suitable `0644` `0444` In fact, unless you actually need to alter the contents of the file. `0444` would be your best choice. --Chris #!/usr/bin/perl -Tw use Perl::Always or die; my $perl_version = (5.12.5); print $perl_version;	[reply]
Re: How to use chmod u +x in perl by Corion (Patriarch) on Nov 25, 2013 at 08:19 UTC
Have you looked at what the documentation about chmod has to say? The examples show the various allowed usages of chmod. Note that `chmod` takes a string. Perl sees `u+x` as the numeric addition of the strings "u" and "x", and thankfully you are using strict so it prohibits using barewords as strings.	[reply] [d/l] [select]
Re: How to use chmod u +x in perl by GrandFather (Saint) on Nov 25, 2013 at 08:18 UTC
You need to use qx() or `` (back ticks) to execute a command line from within Perl (there are other ways as well, but lets keep it simple for now): `my $filename = "sample.pdf"; qx(chmod u+x '$filename');` [download] The single quotes around the file name are only needed if you have unquoted spaces or other special characters in the file name, but do no harm. See Quote and Quote like Operators. True laziness is hard work	[reply] [d/l]
Re: How to use chmod u +x in perl by daxim (Curate) on Nov 25, 2013 at 10:57 UTC
Best solution: `use File::chmod qw(chmod); chmod('u+x', 'sample.pdf');` [download]	[reply] [d/l]
Re: How to use chmod u +x in perl by Anonymous Monk on Nov 25, 2013 at 09:45 UTC
Basically, you need to `stat()` the file to get its mode and then do a binary OR with `0100` (which I think is `u+x`) and then `chmod` `$mode, $filename;` `my $mode = (stat($filename))[2]; my $new_mode = $mode \| 0100; chmod $mode, $filename);` [download]	[reply] [d/l] [select]
Re^2: How to use chmod u +x in perl by Anonymous Monk on Nov 25, 2013 at 09:53 UTC
A few typos crept into that answer, but I'm sure you'll spot them...	[reply]
Re: How to use chmod u +x in perl by taint (Chaplain) on Nov 25, 2013 at 14:14 UTC
Because TMTOWTDI. May I suggest you can also `qx(chmod 0705 '$filename');` [download] or `qx(chmod 0755 '$filename');` [download] These would circumvent any possibility of Perl's misunderstanding the "`u+x`". If that actually applies. --Chris #!/usr/bin/perl -Tw use Perl::Always or die; my $perl_version = (5.12.5); print $perl_version;	[reply] [d/l] [select]
Re^2: How to use chmod u +x in perl by Tux (Canon) on Nov 25, 2013 at 16:47 UTC
Just as what GrandFather was suggesting, this fails badly if `$filename` has a `'` in the name. IF you'd choose a system call instead of the builtin chmod, then at least do it the safe way: `system "chmod", "u+x", $filename;` [download] If someone cares to set the `x` bit on a PDF document, it is likely that the document name is littered with unexpected characters. In the end I'd advice NOT to use `system` or `qx{}` to do a simple `chmod`. Not even to give a fast and simple workaround. I think it is bad advice. Enjoy, Have FUN! H.Merijn	[reply] [d/l] [select]