From: Alain Magloire <alainm AT rcsm DOT ece DOT mcgill DOT ca>
Message-Id: <199905061415.KAA00955@mccoy2.ECE.McGill.CA>
Subject: Re: realpath()
To: djgpp-workers AT delorie DOT com
Date: Thu, 6 May 1999 10:15:56 -0400 (EDT)
In-Reply-To: <Pine.SUN.3.91.990506101056.2814I-100000@is> from "Eli Zaretskii" at May 6, 99 10:11:17 am
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Bonjour

> 
> On Wed, 5 May 1999, Frank Heckenbach wrote:
> 
> > do you plan to support the realpath() function?
> 
> Nobody asked for it until now (personally, I didn't even know such a
> function existed on Unix platforms).
> 
> It should be easy to add a simple wrapper around _fixpath.  Volunteers
> are welcome ;-)
> 
> > AFAICS, the _fixpath() function is functionally
> > mostly equivalent, but the underscore suggests that it's not meant
> > for use from normal programs!?
> 
> The underscore simply means that the name is not in any standard.  A
> library is allowed to use such names without caring about name-space
> conflicts.

realpath() is not part of Posix.1, but it is in the Unix98 std :
On Un*x, one could use :
bash> cat resolv.c
#include <stdlib.h>
#include <limits.h>
#include <stdio.h>
int main (int argc, char ** argv)
{
   char buffer [PATH_MAX];
   char * path ;
   if (argc == 2)
     p = argv[1];
   else
     p = ".";
   if (realpath(p, buffer) == 0)
      perror("realpath");
   else
      printf("%s ==> %s\n", p, buffer);
   return 0;
}
bash> make resolv
gcc resolv.c -o resolv
bash> resolv ../PlayGround/resolv.c
../PlayGround/resolv.c ==> /home/alain/PlayGround.c
bash> uname -rs
SunOS 5.6

------
Such functions are usually not very portable, for example on QNX wich
is is a distributed system, the node number is also part of the path.
So if you want to access a file on node 390:
//390/etc/passwd
//390/dev/ser1
But I must admit seeing it on almost all Un*x variants.

------------------------- for ref -------------------
realpath - resolve a pathname
SYNOPSIS
#include <stdlib.h>
char *realpath(const char *file_name, char *resolved_name);

DESCRIPTION
  The realpath() function derives, from the pathname pointed to by file_name,
  an absolute pathname that names the same file, whose resolution does not
  involve ".", "..", or symbolic links. The generated pathname is stored, up
  to a maximum of {PATH_MAX} bytes, in the buffer pointed to by resolved_name.
RETURN VALUE
  On successful completion, realpath() returns a pointer to the resolved name.
  Otherwise, realpath() returns a null pointer and sets errno to indicate the
  error, and the contents of the buffer pointed to by resolved_name are
  undefined.
ERRORS
  The realpath() function will fail if: 
  [EACCES] Read or search permission was denied for a component of file_name. 
  [EINVAL] Either the file_name or resolved_name argument is a null pointer. 
  [EIO] An error occurred while reading from the file system. 
  [ELOOP] Too many symbolic links were encountered in resolving path. 
  [ENAMETOOLONG] The file_name argument is longer than {PATH_MAX} or a pathname
  component is longer than {NAME_MAX}. 
  [ENOENT] A component of file_name does not name an existing file or file_name
  points to an empty string. 
  [ENOTDIR] A component of the path prefix is not a directory. 
  The realpath() function may fail if: 
  [ENAMETOOLONG] Pathname resolution of a symbolic link produced an
  intermediate result whose length exceeds {PATH_MAX}. 
  [ENOMEM] Insufficient storage space is available. 
EXAMPLES
None.
APPLICATION USAGE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
getcwd(), sysconf(), <stdlib.h>.

-- 
au revoir, alain
----
Aussi haut que l'on soit assis, on est toujours assis que sur son cul !!!