Why the environment variable is unset after using setenv( )

Question

I wrote a C program in Linux to set the values of environment variables using setenv, but after execution, when I run set or export, the environment variable itself seems to be unset. Why?

Here is the code snippet:

int main()
{
  char *mallocPtr, *callocPtr, *reallocPtr, *memalignPtr, *vallocPtr;
  struct sigaction sa;

  sa.sa_handler=SIGSEGV_handler;
  sigaction(SIGSEGV, &sa, NULL);

  if(setenv("ENV1", "3", 1) == 0)
         printf("ENV1 set to 3\n");
  else
         fprintf(stderr, "setenv failed on ENV1");

Answer 1

The environment variables are set within the context of your program.

When your program exits, you're back in the context from where your program was started.