Just a small snip to rotate logfiles... The files are in the directory with a prefix (file) and a number appended file.1 file.2 file.3 .... This will take the files and rotate them to the next greatest number upto the set history size. I'am sure that it can be done shorter/quicker .. but it's a start!

UPDATE: cleaned up code using blazar's comments
use strict;
use warnings;

my $log_dir   = "dir";
my $log_pre   = "file";
my $hist_size = 10;

foreach(sort {($b =~ m/(\d+)$/)[0] <=> ($a =~ m/(\d+)$/)[0]} <$log_dir
+/$log_pre.*>){
         my $f=$_; 
         s/(\d+)$/$1+1/e;
         if($1 >= $hist_size){ unlink $f; }else{ rename $f,$_; }
}

[download]

Replies are listed 'Best First'.
Re: Rotating Log Files
by tirwhan (Abbot) on Dec 28, 2005 at 11:37 UTC

    Nevermind shorter/quicker, this will not work properly for any processes that keep an open file descriptor to their log file (i.e. almost every daemon process), because the fd will still point at the original inode and therefore keep logging to the now rotated file. For most daemons you need to send a SIGHUP to the parent process to reinitialise the logging. Take a look at the logrotate documentation and code for more details on this. That does not invalidate your code (it obviously still works for other processes), just thought I'd mention it.


    A computer is a state machine. Threads are for people who can't program state machines. -- Alan Cox
[reply]
[d/l]

      That is correct.. I should have been more clear in my description.. This is actually more a snip for keeping a history of files instead of a history of logfiles... (I use it for rotating intermediate files used in NIS edited by many people using a 'special' script).

      Go Fish!

[reply]

        Aah, I see. Well, while I'm giving unbidden advice ;-), I've found that in situations such as you describe it is beneficial to use an SCM software such as subversion. This makes it easy for many people to collaborate without one accidentally overwriting someone else's changes and gives you a nice history of who changed what when. Also, channeling the update through a repository action gives you another hook to add custom behaviour. Just a thought.


        A computer is a state machine. Threads are for people who can't program state machines. -- Alan Cox
[reply]
[d/l]
Re: Rotating Log Files
by blazar (Canon) on Dec 28, 2005 at 14:04 UTC

    In addition to tirwhan's most important remark, we also try to enforce the use of strict and warnings all the time, which your code doesn't: even if this is just a tiny snippet, it may contribute to spreading {bad, dangerous} programming techniques.

    Also, using the ternary operator ?: just for his side effects is generally frowned upong, unless in golf or obfu, that is.

    Last, even if this is to be considered only a portion of code and not a whole program, I think there's a typo in the glob: you probably mean $log_dir instead of log_dir.

[reply]
[d/l]
[select]
      Thanks to the remarks, I have added them to the snippit.. I always use strict and warnings, but left them out here since this is only a snippit

      Also, using the ternary operator ?: just for his side effects is generally frowned upong, unless in golf or obfu, that is.

      Which are the side-effects of this operator? I have never experienced any...

      Go Fish!

[reply]
        Which are the side-effects of this operator? I have never experienced any...

        But... you're using them, nevertheless! Generally one should use if (and else) for flow control and ?: to operate on values, e.g.

        if (something) {
    do 'this';
} else {
    do 'that';
}

do (something ? 'this' : 'that');

        [download]

        Of course ?: also acts like an "if-then-else" and you can use it like that. But that's what is generally considered a side effect, since you're discarding its return value which its key feature.

[reply]
[d/l]
[select]

Back to Cool Uses for Perl