Q43428

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Q43428: The Storage of Environment Variables

Article: Q43428
Version(s): 5.10   | 5.10
Operating System: MS-DOS | OS/2
Flags: ENDUSER | S_QuickC
Last Modified: 17-MAY-1989

Question:

How can I find out where the environment variables (PATH, LIB, etc.)
are being stored?

Response:

The environment variables are stored in the near heap, which is part
of DGROUP. The ENVIRON variable is an array of pointers to the strings
that constitute the process environment. The C start-up code takes the
environment information and initializes the ENVIRON variable to point
to the environment table. The function getenv() uses the ENVIRON
variable to access the environment table. ENVIRON can be used to
obtain the environment table address directly.

The following program will print out the address of the beginning of
the environment table and the PATH environment variable:

#include <stdlib.h>
#include <stdio.h>

char *path;

void main (void)
{
  path = getenv( "PATH" );
  printf( "path: %s\nenviron: %x\n", path, environ );
}