Re: File handling basics

As already suggested by vinoth.ree, but somewhat buried in a longer post, I would recommend using the glob which makes things easier that the opendir/readdir combination for 2 reasons: glob does not return the . and .. special entries (wgich you don't want to process) and returns files with their path. So you could simply write:

my $dir = "/temp/";
for my $file (glob "$dir/*") {
    next unless -f $file; # process only regular files, not dirs
    open (my $F, $file) or die "cannot open file $!";
    while (<$F>){
        print $_;
    }
    close $F;
}
# closedir(DIR); -- not needed with glob
[download]

I made a few additional changes reflecting the currently widely accepted good practices.

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Re^2: File handling basics by Monk::Thomas (Friar) on Jul 17, 2015 at 15:15 UTC
I made a few additional changes reflecting the currently widely accepted good practices. you missed one ;) `- open (my $F, $file) or die "cannot open file $!"; + open (my $F), '<', $file or die "cannot open file $!";` [download] @OP: If for some reason you have a file '>123.txt', then open (my $F, $file) would open the file for writing and truncate it. Two purely cosmetical changes would be to replace $F with $fh and also add the filename to the error message, like "cannot open file '$file': $!". @OP: I would consider replacing 'die' with 'warn and next', so that you can process the remaining files even if one is not readable to the current user. Variant a) `open (my $F), '<', $file or warn "cannot open file '$file': $!"; defined $F or next;` [download] Variant b) `open (my $F), '<', $file or warn "cannot open file '$file': $!" and next;` [download] I prefer Variant a) because chaining conditionals may lead to surprises. Mostly because 'or' short circuits the evaluation and due to operator precedence.	[reply] [d/l] [select]
Re^3: File handling basics by Laurent_R (Canon) on Jul 17, 2015 at 17:58 UTC
you missed one ;) Yes, indeed, Monk::Thomas, you're right, I missed one good-practice improvement, and a quite important one. The three-argument syntax for open has been around for quite a number of years and is definitely better than the old two-arguments syntax. Thank you for pointing out this.	[reply]
Re^2: File handling basics by marinersk (Priest) on Jul 17, 2015 at 20:59 UTC
I am also happy to report that a spot check of `glob`demonstrates no immediate ability to confuse it or get the wrong answers back. Way back in the old days it failed frequently for me in a Windows environment -- I no longer remember how, but suspect the use of drive letters and current directory on each were amongst the issues. However, I threw, off the cuff, a bunch of potential curve balls at `glob`recently and I was very happy to discover it worked perfectly on every test I could think of in 90 seconds. Hardly deterministic, but I used to be able to break it without having to work at it, so something has gotten better -- or perhaps I have simply become less warped.	[reply] [d/l] [select]