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

[Thomas H. <tph...@gm...>]

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?

I'd like to be able to do something like what I attempted in
make-out-bad.sh, eg, hook up gnuplot to an arbitrary source of input,
and then pipe it out to wherever. Otherwise, I'm stuck feeding gnuplot
files, can't use arbitrary stdin under all circumstances.

***********************

hartman@ds0207:~/learning/gnuplot>gnuplot --version
gnuplot 4.0 patchlevel 0

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