Re: piping stdin to gnuplot to postscript viewer --one way works, the other doesn't. is this a bug?

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

On Friday 16 March 2007 08:00, Thomas Hartman wrote:
> I have two commands, that it seems to me should have the same result:
> a plot is opened with a postscript viewer.
> 
> However, with one way the postscript output can be read, and with the
> other it can't.
> 
> I also show the diff of the output below.
> 
> Is this as it should be, or a bug?

Incorrect command issued from the bash prompt.
This would have worked from csh/tcsh but you need to be more careful
if you are using bash.

Your command:

  cat save-sin.plt | gnuplot - > out-bad.ps

Correct command:

  cat save-sin.plt | gnuplot > out-good.ps

Note the important difference:

  If gnuplot sees "-" in the command line, it enters interactive mode
  and issues user prompts on stderr.  Your bash command redirects both
  the user prompts (stderr) and the plot (stdout) into a file.


> hartman@ds0207:~/learning/gnuplot>cat make-out-bad.sh
> #!/bin/bash
> outfile=out-bad.ps
> rm -f $outfile
> ( cat save-sin.plt | gnuplot - ) > out-bad.ps;
> kghostview $outfile;
> #rm $outfile
> 
> hartman@ds0207:~/learning/gnuplot>cat make-out-good.sh
> #!/bin/bash
> outfile=out-good.ps
> rm -f $outfile
> ( gnuplot save-sin.plt ) > $outfile;
> kghostview $outfile;
> #rm $outfile
> 
> hartman@ds0207:~/learning/gnuplot>cat save-sin.plt
> # File name: save.plt - save a Gnuplot plot as a PostScript file
> set terminal postscript portrait enhanced mono dashed lw 1 "Helvetica" 14
> plot sin(x)
> 
> hartman@ds0207:~/learning/gnuplot>./compare-out-good-out-bad.sh
> Terminal type set to 'postscript'
> Options are 'portrait enhanced monochrome blacktext \
>    dashed dashlength 1.0 linewidth 1.0 defaultplex \
>    palfuncparam 2000,0.003 \
>    butt "Helvetica" 14'
> 
> 1c1
> < gnuplot> gnuplot> gnuplot> %!PS-Adobe-2.0
> ---
> > %!PS-Adobe-2.0
> 3c3
> < %%CreationDate: Fri Mar 16 15:49:56 2007
> ---
> > %%CreationDate: Fri Mar 16 15:49:54 2007
> 638c638
> < gnuplot> %%Trailer
> ---
> > %%Trailer

-- 
Ethan A Merritt            Courier Deliveries: 1959 NE Pacific
Dept of Biochemistry
Health Sciences Building
University of Washington - Seattle WA 98195-7742