ref: 1ab2fed7a456e1ee1fcaf7b3a046ae6eaa060ba3
dir: /sys/src/ape/lib/ap/gen/putenv.c/
#include <stdlib.h> extern char **environ; int putenv(const char *str) { char *s1, *s2, **e; int n; for(n = 0; s2 = environ[n]; n++) for(s1 = str; *s1 == *s2; s1++, s2++) if(*s1 == '\0' || *s1 == '='){ environ[n] = str; return 0; } e = realloc(environ, (n+1) * sizeof(char*)); if(e == 0) return -1; environ = e; e[n++] = str; e[n] = 0; return 0; }