Re: Files and pipes only?

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

On Friday 15 February 2008 15:54, Scott Worley wrote:
> Why are data files required to be regular files or pipes?

I don't know.

> There's a S_ISREG or S_ISFIFO check performed in src/datafile.c around 
> line 1303.
> 
> I often use bash's <() process substitution syntax to generate data to 
> plot.  

I do not quite follow what you mean. Could you please provide an example
set of commands?   The thing that confuses me is that if you type a 
command like
   plot '< (grep toe ~/aardvarks)' using lines

it should work without passing through the code at line 1303,
because the '<' is trapped as a special case and treated separately
(line 1276).

To prove the point, here is the output from a stupid test run:
gnuplot> plot '/dev/null'
              ^
         "/dev/null" is not a regular file or pipe
         util.c: Success

gnuplot> plot '< (cat /dev/null)'
              ^
         warning: Skipping data file with no valid points
                                 ^
         x range is invalid




> This works great in GNU/Linux, and worked in FreeBSD, OpenBSD,  
> and NetBSD with bash versions less than 3.2.  Starting with bash 3.2.0, 
> bash uses /dev/fd/63 and similar for these substitutions.  In Linux, 
> these "devices" are pipes -- they are S_ISFIFO.  In *BSD, they are 
> character devices -- S_ISCHR.
> 
> What is the S_ISREG or S_ISFIFO test for, anyway?  It's been in gnuplot 
> since the sourceforge cvs import (rev 1.1, 1999), so there's no commit 
> log there to explain the reason for adding it.  Also, the test is simply 
> skipped ifndef HAVE_SYS_STAT_H.
> 
> 
> Removing the test from gnuplot allowed my graphing scripts to work in 
> *BSD again.
> 
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-- 
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle 98195-7742