[Proj] Finding PROJ_LIB from application

[Glynn Clements]

Roger Bivand wrote:

> Is there any way to query the system for the path to lib - effectively the 
> path value in sysname in pj_open_lib.c, line 184? From inside R, I'd like 
> to be able to show which path is being used.

There doesn't appear to be any explicit support for this, but there
are a couple of hacks available if "don't know" isn't fatal:

1. Set PROJ_DEBUG, (temporarily) point stderr at a file, and parse the
filename out of the debug message (which could contain other text if
library functions or the finder function write to stderr).

2. Make a copy of pj_open_lib() which returns the path rather than
opening it, call fstat(fileno(fp)) and stat(pathname), and check that
the dev/inode match.

3. On Linux, use fileno() to get a descriptor from the returned FILE*
and look up the filename in /proc/self/fd/<fd>. Some other Unices
support /proc, but I don't know how consistent they are.

4. On Windows, GetFinalPathNameByHandle(_get_osfhandle(_fileno(fp))).

-- 
Glynn Clements <glynn at gclements.plus.com>