The tcgetpgrp() function shall return the value of the process group ID
of the foreground process group associated with the terminal.
If there is no foreground process group, tcgetpgrp() shall return a value
greater than 1 that does not match the process group ID of any existing
The tcgetpgrp() function is allowed from a process that is a member of a
background process group; however, the information may be subsequently changed
by a process that is a member of a foreground process group.
Upon successful completion, tcgetpgrp() shall return the value of the
process group ID of the foreground process associated with the terminal.
Otherwise, -1 shall be returned and errno set to indicate the error.
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html