osx man page for tcgetsid

tcgetsid(3)						   BSD Library Functions Manual 					       tcgetsid(3)

NAME
     tcgetsid -- get the process group ID for the session leader for the controlling terminal

SYNOPSIS
     #include <termios.h>

     pid_t
     tcgetsid(int fildes);

DESCRIPTION
     The tcgetsid() function obtains the process group ID of the session for which the terminal specified by fildes is the controlling terminal.

RETURN VALUES
     Upon successful completion, tcgetsid() returns the process group ID associated with the terminal.	Otherwise, a value of (pid_t)-1 is
     returned and errno is set to indicate the error.

ERRORS
     The tcgetsid() function will fail if:

     [EACCES]		The fildes argument is not associated with a controlling terminal.

     [EBADF]		The fildes argument is not a valid file descriptor.

     [ENOTTY]		The file associated with fildes is not a terminal.

SEE ALSO
     getsid(2), setpgid(2), setsid(2), tcgetpgrp(3), termios(4)

STANDARDS
     The tcgetsid() function conforms to IEEE Std 1003.1-2001 (``POSIX.1'').

BSD
								 December 20, 2003							       BSD