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OpenDarwin 7.2.1 - man page for getpgid (opendarwin section 2)

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GETPGRP(2)			     BSD System Calls Manual			       GETPGRP(2)

     getpgrp -- get process group

     Standard C Library (libc, -lc)

     #include <unistd.h>


     getpgid(pid_t pid);

     The process group of the current process is returned by getpgrp().  The process group of the
     process identified by pid is returned by getpgid().  If pid is zero, getpgid() returns the
     process group of the current process.

     Process groups are used for distribution of signals, and by terminals to arbitrate requests
     for their input: processes that have the same process group as the terminal are foreground
     and may read, while others will block with a signal if they attempt to read.

     This call is thus used by programs such as csh(1) to create process groups in implementing
     job control.  The tcgetpgrp() and tcsetpgrp() calls are used to get/set the process group of
     the control terminal.

     The getpgrp() call always succeeds.  Upon successful completion, the getpgid() call returns
     the process group of the specified process; otherwise, it returns a value of -1 and sets
     errno to indicate the error.

     getpgid() will succeed unless:

     [ESRCH]		there is no process whose process ID equals pid

     getsid(2), setpgid(2), termios(4)

     The getpgrp() function call appeared in 4.0BSD.  The getpgid() function call is derived from
     its usage in System V Release 4.

     The getpgrp() function call is expected to conform to ISO/IEC 9945-1:1990 (``POSIX.1'').

     This version of getpgrp() differs from past Berkeley versions by not taking a pid_t pid
     argument.	This incompatibility is required by ISO/IEC 9945-1:1990 (``POSIX.1'').

     From the ISO/IEC 9945-1:1990 (``POSIX.1'') Rationale:

     4.3BSD provides a getpgrp() function that returns the process group ID for a specified
     process.  Although this function is used to support job control, all known job-control
     shells always specify the calling process with this function.  Thus, the simpler AT&T
     System V UNIX getpgrp() suffices, and the added complexity of the 4.3BSD getpgrp() has been
     omitted from POSIX.1.  The old functionality is available from the getpgid() function.

BSD					   June 4, 1993 				      BSD
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