OS X undocumented __pthread_chdir() and __pthread_fchdir() syscalls

pthread_chdir.c

#include <stdio.h>
#include <stdlib.h>

#include <sys/syscall.h>
#include <unistd.h>
#include <fcntl.h>

#ifndef SYS___pthread_chdir
# define SYS___pthread_chdir 348
#endif

#ifndef SYS___pthread_fchdir
# define SYS___pthread_fchdir 349
#endif

int __pthread_chdir(const char *path)
{
  return syscall(SYS___pthread_chdir, path);
}

int __pthread_fchdir(int dirfd)
{
  return syscall(SYS___pthread_fchdir, dirfd);
}

int main(void)
{
  int dirfd;

  dirfd = open("/", O_RDONLY);
  if (dirfd == -1)
    perror("open"), exit(1);

  if (__pthread_chdir("/"))
    perror("__pthread_chdir");

  if (__pthread_fchdir(dirfd))
    perror("__pthread_fchdir");

  return 0;
}