sigsend(S)

sigsend, sigsendset -- send a signal to a process or a group of processes

Synopsis

   #include <sys/types.h>
   #include <signal.h>
   #include <sys/procset.h>
   
   int sigsend(idtype_t idtype, id_t id, int sig);
   

   int sigsendset(const procset_t *psp, int sig);

Description

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 signal(M). If sig is zero (the null signal), error checking is performed but no signal is actually sent. This value can be used to check the validity of id and idtype.

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 [from exec(2)] 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 ID id.

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 ID id.

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 [see priocntl(S)].

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 process.

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:

   idop_t       p_op;
   idtype_t     p_lidtype;
   id_t         p_lid;
   idtype_t     p_ridtype;
   id_t         p_rid;

p_lidtype and p_lid specify the ID type and ID of one (``left'') set of processes; p_ridtype and p_rid specify the ID type and ID of a second (``right'') set of processes. ID types and IDs are specified just as for the idtype and id arguments to sigsend. p_op 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 p_op and the processes they specify are:

POP_DIFF: set difference: processes in left set and not in right set
POP_AND: set intersection: processes in both left and right sets
POP_OR: set union: processes in either left or right set or both
POP_XOR: set exclusive-or: processes in left or right set but not in both

Return values

On success, sigsend and sigsendset return 0. On failure, sigsend and sigsendset return -1 and set errno to identify the error.

Errors

In the following conditions, sigsend and sigsendset fail and set errno to:

EINVAL: sig is not a valid signal number.
EINVAL: idtype is not a valid idtype field.
EPERM: sig is SIGKILL, idtype is P_PID and id is 1 (proc1).
EPERM: The calling process does not have the P_OWNER 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.
ESRCH: No process can be found corresponding to that specified by id and idtype.

In addition, sigsendset fails if:

EFAULT: psp points outside the process's allocated address space.

References

getpid(S), kill(C), kill(S), priocntl(S), signal(S), signal(M)

Notices

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. See signal(M) for further details. See thr_kill(THREAD) and pthread_kill(PTHREAD) for details of intra-process signaling between threads.