input and output redirection in unix system in c language. very helpful in Networks Programming

redirect.c

/**
 * Author: Rajmani Arya
 * Originally By: http://stackoverflow.com/users/121747/jack
 */
static int fd_in, fd_out;
static fpos_t pos_in, pos_out;

void switchStdin(const char *newStream)
{
  fflush(stdin);
  fgetpos(stdin, &pos_in);
  fd_in = dup(fileno(stdin));
  freopen(newStream, "r", stdin);
}

void revertStdin()
{
  fflush(stdin);
  dup2(fd_in, fileno(stdin));
  close(fd_in);
  clearerr(stdin);
  fsetpos(stdin, &pos_in);
}

void switchStdout(const char *newStream)
{
  fflush(stdout);
  fgetpos(stdout, &pos_out);
  fd_out = dup(fileno(stdout));
  freopen(newStream, "w", stdout);
}

void revertStdout()
{
  fflush(stdout);
  dup2(fd_out, fileno(stdout));
  close(fd_out);
  clearerr(stdout);
  fsetpos(stdout, &pos_out);
}