Change permissions after file is created

ddrew78 has asked for the wisdom of the Perl Monks concerning the following question:

Greetings Monks, I currently have a perl script that generates a new file every time it is run. After it has completed, I want it to change permissions on that file. What I'm currently using is

close $outfile; 
system 'chmod 777 $outfile';
[download]

However, this gives me an error every time I execute the script, and it does not change the permissions

chmod: missing operand after `777'

Any ideas as to what I'm doing wrong here? Any and all help is, as always, highly appreciated.

Comment on Change permissions after file is created Select or Download Code

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Re: Change permissions after file is created by marto (Cardinal) on Jul 08, 2014 at 20:35 UTC
Consider the follwing: `#!/usr/bin/perl # save as out.pl use strict; use warnings; my $output = "out.pl"; system('dir $output'); print "\n\n--------------\n\n"; system("dir $output");` [download] See Strings in Perl: quoted, interpolated and escaped. There is no need to call system to chmod a file, see chmod.	[reply] [d/l]
Re: Change permissions after file is created by AppleFritter (Vicar) on Jul 08, 2014 at 20:27 UTC
Guessing from the two lines of code you shared, `$outfile` most likely contains a filehandle, not a filename. Pass a filename to chmod instead, and all should be fine. EDIT: also, as boftx pointed out, single quotes will keep perl from interpolating the variable into your string, so `$outfile` is being interpreted by your shell instead -- and most likely evaluates to the empty string, hence the error message.	[reply]
Re^2: Change permissions after file is created by boftx (Deacon) on Jul 08, 2014 at 21:05 UTC
Good catch on the filehandle. I overlooked that and just focused on a scalar inside single quotes. You must always remember that the primary goal is to *drain the swamp* even when you are hip-deep in alligators.	[reply]
Re: Change permissions after file is created by Laurent_R (Canon) on Jul 08, 2014 at 22:50 UTC
1. Don't use system commands on filehandles, but on actual files (file names); 2. Use the internal Perl `chmod` function rather than a system call; 3. The internal system call requires an octal number for permissions. So try something like: `chmod 0777, $outfile;` [download]	[reply] [d/l] [select]
Re: Change permissions after file is created by boftx (Deacon) on Jul 08, 2014 at 20:29 UTC
Try using double quotes (") instead of single quotes (') so that $outfile is interpolated into the string. Beyond that, read the docs for system and switch to the multi-argument style to avoid some nasty security holes. You must always remember that the primary goal is to *drain the swamp* even when you are hip-deep in alligators.	[reply]