TCGETPGRP(3) BSD Programmer's Manual TCGETPGRP(3)
tcgetpgrp - get foreground process group ID
The tcgetpgrp function returns the value of the process group ID of the
foreground process group associated with the terminal device. If there
is no foreground process group, tcgetpgrp returns an invalid process ID.
If an error occurs, tcgetpgrp returns -1 and the global variable errno is
set to indicate the error, as follows:
[EBADF] The fd argument is not a valid file descriptor.
[ENOTTY] The calling process does not have a controlling terminal or
the underlying terminal device represented by fd is not the
setpgid(3), setsid(2), tcsetpgrp(3)
The tcgetpgrp function is expected to be compliant with the IEEE
Std1003.1-1988 (``POSIX'') specification.
4.4BSD June 4, 1993 1