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NAME

     getpgrp - get process group

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <unistd.h>

     pid_t
     getpgrp(void);

     pid_t
     getpgid(pid_t pid);

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

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() system call 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() system call.

ERRORS

     The getpgid() system call will succeed unless:

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

SEE ALSO

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

STANDARDS

     The getpgrp() system call is expected to conform to ISO/IEC 9945-1:1990
     (“POSIX.1”).

HISTORY

     The getpgrp() system call appeared in 4.0BSD.  The getpgid() system call
     is derived from its usage in AT&T System V.4 UNIX.