[HRPM] Sorting and array of lines returned from 'ps'

[chicks at chicks.net]

On Tue, 21 Nov 2000, Scott Cornette wrote:

> Once you have decided on which field you want sorted, you can try
> sorting the array using the perl sort operator with a subroutine
> passed as an argument.  This will allow you to do comparisons by
> choosing whether you want a numeric or ASCII sort.  For example, to
> sort a numeric field:
> 
>      sub numerically { $a <=> $b; }
> 
>      @sorted_array = sort numerically @unsorted_array;
> 
> To sort a field of strings (ASCII based):
> 
>      sub ascii_string { $a cmp $b; }
> 
>      @sorted_array = sort ascii_string @unsorted_array;
> 
> There are plenty of examples in the Camel book and Cookbook.

That's precisely what I was thinking of doing for him.  But instead of a
single operation like ascii_string (which is redundant since that's 'cmp'
is what sort uses by default!) ... I was thinking of something like:

sub pid_array {
	($x,$x,$x,$pida) = split (/ /,$a);
	($x,$x,$x,$pidb) = split (/ /,$b);
	$pida <=> $pidb;
}

@sortedprocs = sort pid_array @rawprocs;

Two things are relevant here:

- The value of the last line of a sub is used as the return value if there
is no explicit return value.  This is a side effect and isn't as explicit
as I'd like, but it's common practice and it's good to be familiar with
it.

- <=> and cmp are special in that they return -1 for less than, 0 for
equal and 1 for greater than -- which is exactly what sort needs.  If your
sub returns those values consisantly, you don't need to use those
operators to generate them.

And as everyone has said the Camel (/Programming Perl/) and the Cookbook
have lot's of useful information.  I've got Camel 3E on my night stand
and I'm hoping to dig into in the next few weeks!

-- 
</chris> (My God, there's HRPM list traffic!  Yay.)

"Pinky, you've left the lens cap of your mind on again." - The Brain