[Info-vax] Porting logical name applications to Unix

[Bob Koehler]

In article <icSdnWlrjO48rVzXnZ2dnUVZ_hqdnZ2d at earthlink.com>, "John Reagan" <johnrreagan at earthlink.net> writes:
> 
> Alan is talking about the CRTL's caching of getenv() calls and whether it 
> should do another $TRNLNM behind your back.  For certain things, a single 
> translation once is all you need.  For other things, you'd actually want to 
> translate again so be careful.
> 
>        Performance Optimizations:         default setting
> 
>           DECC$ENABLE_GETENV_CACHE        DISABLE
>           DECC$LOCALE_CACHE_SIZE          0
>           DECC$TZ_CACHE_SIZE              2

   OK, that's an advantage of logical names that AFAIK can be emulated on 
   UNIX only through links:  the file system automatically finds the target
   without an explicit getenv().

   getenv() looking at both DCL symbols and logical names on VMS does provide
   some capabilities that it doesn't have on UNIX, but that can lead to
   confusion.  Since VMS' getenv() looks at logical names first, the 
   following example shows how setting up a both has the documented behaviour,
   which might not be what a newbie from UNIX land would expect when
   translating a shell script that set an environment variable to a DCL
   script that sets a DCL symbol:

eisner> type a.c
#include <stdio.h>
#include <stdlib.h>

main ()
{
   char *a = getenv("A");
   if (a) printf("%s\n",a);
}

eisner> define a b
eisner> r a.exe
B
eisner> a:=c
eisner> r a.exe
B
eisner> deass a
eisner> r a.exe
C