sigsend, sigsendset --
send a signal to a process or a group of processes
int sigsend(idtype_t idtype, id_t id, int sig);
int sigsendset(const procset_t *psp, int sig);
sigsend sends a signal to the process or group of processes specified
by id and idtype.
The signal to be sent is specified by sig and is either zero
or one of the values listed in
If sig is zero (the null signal), error checking is performed but no signal is
This value can be used to check the validity of id and
In order to send the signal to the target process (pid),
the sending process must have permission to do so, subject to the
following ownership restrictions:
The real or effective user ID of the sending process must match
the real or saved
user ID of the receiving process, unless
the sending process has the P_OWNER privilege, or
sig is SIGCONT and the sending process has the same session
ID as the receiving process.
If idtype is P_PID, sig is sent to the process with process
If idtype is P_PGID, sig is sent to any process with process
group ID id.
If idtype is P_SID, sig is sent to any process with session
If idtype is P_UID, sig is sent to any process with
effective user ID id.
If idtype is P_GID, sig is sent to any process with
effective group ID id.
If idtype is P_CID, sig is sent to any process with
scheduler class ID id
If idtype is P_ALL, sig is sent to all processes and
id is ignored.
If id is P_MYID, the value of id is taken from the calling
The process with a process ID of 0 is always excluded.
The process with a
process ID of 1 is excluded unless idtype is equal to P_PID.
sigsendset provides an alternate interface for sending signals to
sets of processes.
This function sends signals to the set of processes specified by psp.
psp is a pointer to a structure of type procset_t, defined in
sys/procset.h, which includes the following members:
specify the ID type and ID of one (``left'') set of processes;
specify the ID type and ID of a second (``right'') set of processes.
ID types and IDs are specified just as for the
specifies the operation to be performed on the two sets of processes to get
the set of processes the system call is to apply to.
The valid values for
and the processes they specify are:
set difference: processes in left set and not in right set
set intersection: processes in both left and right sets
set union: processes in either left or right set or both
set exclusive-or: processes in left or right set but not in both
On success, sigsend and sigsendset return 0.
On failure, sigsend and sigsendset return -1 and
set errno to identify the error.
In the following conditions, sigsend and sigsendset fail and set errno to:
sig is not a valid signal number.
idtype is not a valid idtype field.
sig is SIGKILL, idtype is P_PID and id
is 1 (proc1).
The calling process does not have the
privilege, the real or effective user ID of the sending process
does not match the real or effective user ID of the
receiving process, and the calling process is not sending SIGCONT to a
process that shares the same session.
No process can be found corresponding to that specified by id and
In addition, sigsendset fails if:
psp points outside the process's allocated address space.
Considerations for threads programming
Signals can be posted from one process to the designated processes
via the sigsend system call
but not to specific threads within those processes.
for further details.
for details of intra-process signaling between threads.
© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 25 April 2004