psignal(9)

NAME

psignal, pgsignal, gsignal - post signal to a process or

process group

SYNOPSIS

#include <sys/types.h>
#include <sys/signalvar.h>
void
psignal(struct proc *p, int signum);
void
pgsignal(struct pgrp *pgrp, int signum, int checkctty);
void
gsignal(int pgid, int signum);

DESCRIPTION

These functions post a signal to one or more processes. The

argument
signum common to all three functions should be in the range

[1-NSIG].

The psignal() function posts signal number signum to the

process represented by the process structure p. With a few exceptions

noted below,
the target process signal disposition is updated and is

marked as
runnable, so further handling of the signal is done in the

context of the
target process after a context switch. Note that psignal()

does not by
itself cause a context switch to happen.

The target process is not marked as runnable in the follow

ing cases:

+o The target process is sleeping uninterruptibly.

The signal

will be noticed when the process returns from the

system call
or trap.

+o The target process is currently ignoring the sig

nal.

+o If a stop signal is sent to a sleeping process

that takes the

default action (see sigaction(2)), the process is

stopped without awakening it.

+o SIGCONT restarts a stopped process (or puts them

back to sleep)

regardless of the signal action (e.g., blocked or

ignored).

If the target process is being traced psignal() behaves as

if the target
process were taking the default action for signum. This al

lows the tracing process to be notified of the signal.

The pgsignal() function posts signal number signum to each

member of the
process group described by pgrp. If checkctty is non-zero,

the signal
will be posted only to processes that have a controlling

terminal.
pgsignal() is implemented by walking along the process list

headed by the
field pg_members of the process group structure pointed at

by pgrp and
calling psignal() as appropriate. If pgrp is NULL no action

is taken.

The gsignal() function posts signal number signum to each

member of the
process group identified by the group id pgid. gsignal()

first finds the
group structure associated with pgid, then invokes

pgsignal() with the
argument checkctty set to zero. If pgid is zero no action

is taken.

SEE ALSO

sigaction(2), signal(9), tsleep(9)

BSD June 22, 1996

BSD