[Plplot-devel] -h command-line issue on Cygwin

[Alan W. I. <ir...@be...>]

On 2018-01-07 11:03-0000 Arjen Markus wrote:

> There is a small issue though with the gfortran compiler under
Cygwin. I do not understand it (*) but here is the output to screen if
I use the -h option:

> $ ./x01f -h
> pl_parse_dynamic =  T
> argv before call to plparseopts(..., PL_PARSE_SKIP)
> i =   0, argument = ./x01f
> i =   1, argument = -h
> /bin/sh: C:\Program: command not found
>
>
> This does not happen for Intel Fortran - then I get an overview of all the options that are available.
>
> (*) From a closer look at the code I think this is due to the fragment:
>
> #ifdef HAVE_POPEN
>
>    FILE *pager = NULL;
>
>    if ( getenv( "PAGER" ) != NULL )
>
>        pager = (FILE *) popen( "$PAGER", "w" );
>
>    if ( pager == NULL )
>
>        pager = (FILE *) popen( "more", "w" );
>
>    if ( pager != NULL )
>
>        outfile = pager;
>
> #endif
>
> It is probably trying to run a pager program like "more" but that does not quite work on Cygwin.

Hi Arjen:

Since both x01c and x01f have special command-line parsing, I suggest
the first thing you should do is try other C and Fortran examples
(e.g., x00c or x00f) to see if the -h option works in those less
special cases. My guess is it won't work, i.e., the problem you
discovered with the -h option on Cygwin is a general one for our
standard C and Fortran examples rather than specific to just x01f.

I looked up the popen man page on Linux which states it "opens a
process by creating a pipe, forking, and invoking the shell". So I
assume what the above code fragment does is redirect the normal output
of the -h option from stdout to whatever you have specified as the
PAGER environment variable or the "more" pager as a fallback if you
have not specified PAGER.

So I suspect what has happened on your Cygwin platform is you don't
have any pager installed.  You should be able to fix that by
installing "more" via the "util-linux" package and/or "less" via the
"less" package (while setting your PAGER environment variable to
"less").

Let me know whether one or the other of those two measures fixes the
above -h issue.

By the way, I highly recommend "less" as a much better pager than
"more".  So the developers of "less" used some self-deprecating humor
when they picked the name of their pager.  :-)

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (freeeos.sf.net); the Time
Ephemerides project (timeephem.sf.net); PLplot scientific plotting
software package (plplot.sf.net); the libLASi project
(unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
and the Linux Brochure Project (lbproject.sf.net).
__________________________

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