tcsetpgrp() - set foreground process group ID
#include <sys/types.h>
#include <unistd.h>
int tcsetpgrp (int fd, pid_t pgrp_id)
If the process has a controlling terminal, the tcsetpgrp(2) function sets the foreground process group ID associated with the terminal device to pgrp_id. The terminal device associated with fd must be the controlling terminal of the calling process and the controlling terminal must be currently associated with the session of the calling process. The value of pgrp_id must be the same as the process group ID of a process in the same session as the calling process.
Upon successful completion, tcsetpgrp(2) returns a value of zero.
If an error occurs, tcgetpgrp(2) returns -1 and the global variable errno is set to indicate the error, as follows:
setpgid(2)
setsid(2)
tcgetpgrp(2)