[Za-pm] Regular expression help needed

[Nick Cleaton]

On Mon, Jun 23, 2003 at 02:26:12PM +0200, Pritesh Jewan wrote:
>  
> I have a few regular expressions from a script that I am trying to update
> and needed some assistance with what the expression mean:
>  
> ===============================
> while(<GWTABLE>){
> next if (/^#/);

'next' means jump to the next go around the loop.

'if (/^#/)' means 'if the current line starts with a #'.

So that line jumps to the next go around the while loop (i.e. goes
on to the next line from GWTABLE) if the current line starts with
a '#'.

> next if (/^$/);

Similar, but '$' means the end of the string, so this one does a
'next' if the line is empty.

You don't need the brackets on those, and I find them more readable
without brackets, so I would write those as:

  next if /^#/;
  next if /^$/;

> $match = 1;
>  
> I'm trying to understand the second and third line.
> ===============================
> The script has this line in a few places. Can't seem to find any doco that
> would explain what it means:
>  
> s(\n)();

That deletes the newline from the end of the line.  I prefer to write
that as:

  chomp;

since I find that more readable.

> s/\n$//;

Ditto.  I would also rewrite that as:

  chomp;

> ===============================
> (!/^$/)||next;
> (!/^#/)||next;

Those are confusing double negatives.  They jump to the next go
around the loop if the pattern matches.  I would rewrite those
as:

  next if /^$/;
  next if /^#/;

--
Nick