void xsetenv(const char *en, const char *ev, int overwrite);
void *xrealloc(void *ptr, size_t sz);
void xsetenv(const char *en, const char *ev, int overwrite);
void *xrealloc(void *ptr, size_t sz);
void filter_environment(unsigned flags, const char *prefix_in,
const char *const *patv,
void (*foundone)(const char *fulln, const char *en,
void filter_environment(unsigned flags, const char *prefix_in,
const char *const *patv,
void (*foundone)(const char *fulln, const char *en,