[Novalug] Tutorials

[Rob Payne]

On Sat, Dec 16, 2006 at 10:06:43PM -0500, Kevin Dwyer wrote:
> On Sat, Dec 16, 2006 at 07:38:07PM -0500, Rob Payne wrote:
> > On Sat, Dec 16, 2006 at 01:07:40PM -0500, Kevin Dwyer wrote:
> > > On Sat, Dec 16, 2006 at 12:17:30PM -0500, James Ewing Cottrell 3rd wrote:
> > > > For example, the "print the second field" script above can be expressed 
> > > > as a one-liner in Perl as: ps -ef | perl -lane 'print $F[1]'
> > > 
> > > This is precisely what keeps me from ever writing things in perl.
> > > 
> > > I.E.: Just where the hell did $F come from?  I guess $_ was already
> > > spoken for.
> > 
> > Well, since this is a thread on tutorials, maybe you can offer some
> > advice instead of just criticism?  If you prefer another language,
> > maybe offer some code in that one.
> 
> It can be done in any number of languages.  perl is just full of
> shortcuts so that it can fit in one-line.
> 
> Here's python in one line:

> ps -ef | python -c 'import sys; print "\n".join([line.split()[1] for line in sys.stdin])'

Thanks, I didn't know the incantation to make python do it in
one-line.

> Python isn't meant to be written in one line though, which is why that's
> ugly.  Something better would look like this:

As you said, you can make perl do it in a similar fashion.  I don't
generally resort to one-liners because if I'm scripting something I'll
generally have to do it more than once.  If I need to do it again,
having to re-write the one-liner is a waste.  Here's more like how I'd
do it in perl:

#!/usr/bin/perl

use strict;
use warnings;

my($line) = '';

while ($line = <STDIN>)
{
  if (defined ($line))
  {
    my(@fields) = split(/\s+/, $line);
    print "@fields[1]\n";
  }
}

> And you could make perl look like that too, but no one does because it's
> some sort of faux pas.  (Perl people will say: Why bother when I can do
> it in one line?  So it's a perspective thing, or perhaps a function of
> how deranged one's mind is.)

I'm just a different type of deranged perl person.

				 -rob
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