Re: fileexist(f)

[Ethan M. <merritt@u.washington.edu>]

On Friday 03 March 2006 10:44 am, Petr Mikulik wrote:
> > It seems to me easier to use  system("find . -name <foo> -newer
> > <bar>")
>
> This is not portable either.

Not universally.  But it works without any changes to gnuplot.
Why add a new routine to gnuplot if it doesn't give any advantage
over what you can already do?

> Actually, the most trivial solution seems to be:
I think you meant:

   if (!defined(prev)) prev = ""      # first time only

   new=system("ls -l bla.dat")
   if (new ne prev) plot 'bla.dat'
   prev = new
   pause 5; reread


But this doesn't work very well.
`ls -l` will not tell whether new data has been written since your
previous plot.  For one thing, the time is only given to the nearest
minute. I thought you wanted a real-time test, that would update on
the order of seconds?  There is a gnu-specific extension:
 `ls --full-time`, but this won't help you on general unix boxes and
it certainly won't help on VMS or other less unix-like systems.

Anyhow, is there anysystem that provides "ls" that does not also
provide "find"?

> ??? how to detect that a variable has not been initialized?

if (defined(VAR))


-- 
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle WA