CODEWITHSUNDEEP
perlbashunix
ktm5124
ktm5124

Reputation: 12123

Perl: Is it better to clobber a file or remove it and open a new one?

For example,

#!/usr/bin/perl

open FILE1, '>out/existing_file1.txt'; 
open FILE2, '>out/existing_file2.txt'; 
open FILE3, '>out/existing_file3.txt';

versus

#!/usr/bin/perl

if (-d out) {
    system('rm -f out/*');
}

open FILE1, '>out/new_file1.txt'; 
open FILE2, '>out/new_file2.txt'; 
open FILE3, '>out/new_file3.txt';

In the first example, we clobber the files (truncate them to zero length). In the second, we clean the directory and then create new files.

The second method (where we clean the directory) seems redundant and unnecessary. The only advantage to doing this (in my mind) is that it resets permissions, as well as the change date.

Which is considered the best practice? (I suspect the question is pedantic, and the first example is more common.)

Edit: The reason I ask is because I have a script that will parse data and write output files to a directory - each time with the same filename/path. This script will be run many times, and I'm curious whether at the start of the script I should partially clean the directory (of the files I am writing to) or just let the file handle '>' clobber the files for me, and take no extra measures myself.

Upvotes: 1

Views: 750

Answers (1)

Barmar
Barmar

Reputation: 781096

Other than the permissions issue you mentioned, the only significant difference between the two methods is if another process has one of the output files open while you do this. If you remove the file and then recreate it, the other process will continue to see the data in the original file. If you clobber the file, the other process will see the file contents change immediately (although if it's using buffered I/O, it may not notice it until it needs to refill the buffer).

Removing the files will also update the modification time of the containing directory.

Upvotes: 2

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