C - Changing environment variables
==================================

Public domain
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    int main ()
    {
      int overwrite = 1;
      char *test;
    
      test = getenv("TEST");
      printf("TEST environment variable is %s \n",
          (test != NULL) ? test : "undefined.");
    
      setenv ("TEST", "102030", overwrite);
    
      test = getenv("TEST");
      printf("TEST environment variable is %s \n",
          (test != NULL) ? test : "undefined.");
    
      unsetenv("TEST");
    
      test = getenv("TEST");
      printf("TEST environment variable is %s \n",
          (test != NULL) ? test : "undefined.");
    }
    
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### Output
    
    $ export TEST="hello"
    
    $ ./a.out 
    TEST environment variable is hello 
    TEST environment variable is 102030 
    TEST environment variable is undefined. 
    
    $ echo $TEST
    hello
    
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_BY: Pejman Moghadam_  
_TAG: c, setenv, unsetenv, environment_  
_DATE: 2011-06-02 18:26:42_