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

NAME
     getpgid, getpgrp -- get process group

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <unistd.h>

     pid_t
     getpgid(pid_t pid);

     pid_t
     getpgrp(void);

DESCRIPTION
     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.

RETURN VALUES
     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.

ERRORS
     getpgid() will succeed unless:

     [ESRCH]            There is no process whose process ID equals pid.

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

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

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

COMPATIBILITY
     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