setenv.c raw

   1  #include <stdlib.h>
   2  #include <string.h>
   3  #include <errno.h>
   4  
   5  void __env_rm_add(char *old, char *new)
   6  {
   7  	static char **env_alloced;
   8  	static size_t env_alloced_n;
   9  	for (size_t i=0; i < env_alloced_n; i++)
  10  		if (env_alloced[i] == old) {
  11  			env_alloced[i] = new;
  12  			free(old);
  13  			return;
  14  		} else if (!env_alloced[i] && new) {
  15  			env_alloced[i] = new;
  16  			new = 0;
  17  		}
  18  	if (!new) return;
  19  	char **t = realloc(env_alloced, sizeof *t * (env_alloced_n+1));
  20  	if (!t) return;
  21  	(env_alloced = t)[env_alloced_n++] = new;
  22  }
  23  
  24  int setenv(const char *var, const char *value, int overwrite)
  25  {
  26  	char *s;
  27  	size_t l1, l2;
  28  
  29  	if (!var || !(l1 = __strchrnul(var, '=') - var) || var[l1]) {
  30  		errno = EINVAL;
  31  		return -1;
  32  	}
  33  	if (!overwrite && getenv(var)) return 0;
  34  
  35  	l2 = strlen(value);
  36  	s = malloc(l1+l2+2);
  37  	if (!s) return -1;
  38  	memcpy(s, var, l1);
  39  	s[l1] = '=';
  40  	memcpy(s+l1+1, value, l2+1);
  41  	return __putenv(s, l1, s);
  42  }
  43