getpgrp.2

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 2 代码 · 共 58 行

.\" SCCSID: @(#)getpgrp.2	2.4	8/10/87
.TH getpgrp 2
.SH Name
getpgrp \- get process group
.SH Syntax
.nf
.B #include <sys/types.h>
.B #include <unistd.h>
.PP
.B pgrp = getpgrp(\fIpid\fP)
.B pid_t pgrp;
.B pid_t \fIpid\fP;
.fi
.SH Description
.NXR "getpgrp system call"
.NXA "getpgrp system call" "setpgrp system call"
.NXA "getpgrp system call" "tty interface"
.NXR "process" "getting process group"
.NXR "process group" "defined"
The system call 
.PN getprgrp 
returns the process group of the specified process.
If
.I pid
is zero, the call applies to the current process.
.PP
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 the foreground
and may read, while others block with a signal if they attempt
to read.
.PP
This call is used by programs such as 
.MS csh 1
to create process groups in implementing job control.
The TIOCGPGRP and TIOCSPGRP calls described in 
.MS tty 4
are used to get and set the process group of the control terminal.
.SH Environment
When your program is compiled in the System V or POSIX environment,
.PN getpgrp
is called without arguments and the process group of the
current process is returned.  
.PP
Additionally, in POSIX mode, 
.PN getpgrp 
returns a value type of 
.I pid_t.
.SH Diagnostics
The
.PN getpgrp
call fails under the following condition:
.TP 15
[ESRCH]
No such process, PID.
.SH See Also
getuid(2), setpgrp(2), tty(4)