foreground process group ID
() 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,
() 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:
- The fd argument is not a
valid file descriptor.
- The calling process does not have a controlling terminal or
the underlying terminal device represented by
fd is not the controlling terminal.
() function is expected to be
compliant with the IEEE Std 1003.1-1988