[GRASS5] Problem with r.fill.dir

[Eric G. Miller]

On Fri, May 11, 2001 at 01:45:05PM +0700, Justin Hickey wrote:
> Hi Roger
> 
> When compiling the r.fill.dir program on an SGI with MIPSPro compilers I
> get the following error:
> 
> "main.c", line 52: error(1005): could not open source file "error.h"
>   #include <error.h>

I think we've seen this before (as I tried to use the same thing once).
A good substitute for error() is strerror(), but it may not be supported
everywhere yet ;(.  

> Since the comment for this include statement is associated with lseek,
> can you change lseek to fseek? There are other reasons for using fseek
> as well. First, fseek is a standard library function and lseek is not.
> Second, according to Kernighan and Ritchie's "The C Programming
> Language", lseek can have slower access. Thus, I would suggest changing
> lseek to fseek if possible. Then the error.h file may not be needed.
> 
> Just my 2 cents worth.

lseek and fseek aren't interchangeable; one works with descriptors the
other works with streams.  I don't know why lseek would have slower
access. My understanding is a file stream on *nix typically has a file
descriptor in the FILE struct, so a call to fseek is probably just
translated to a call to lseek.  As far as standards, lseek should exist
on every *nix system (is it POSIX?) and is used all over GRASS library
code.  While the FILE stream interface may be more portable via ANSI C,
the *nix file descriptor interface is generally more flexible.  I'm not
necessarily arguing one over the other, but we shouldn't kid ourselves
as GRASS is heavily entrenched in *nix standards.  

-- 
Eric G. Miller <egm2 at jps.net>

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