#include <signal.h>int sigsend(idtype_t idtype, id_t id, int sig);
The sigsend() function 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 0 or one of the values listed in signal(3HEAD). If sig is 0 (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.
The real or effective user ID of the sending process
must match the real or saved user ID of the receiving
process, unless the effective user ID of the sending
process is super-user, 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 all processes with process group ID id.
If idtype is P_SID, sig is sent to all processes with session ID id.
If idtype is P_TASKID, sig is sent to all processes with task 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_PROJID, sig is sent to any process with project ID id.
If idtype is P_CID, sig is sent to any process with scheduler class ID id (see priocntl(2)).
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.
The sigsendset() function 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;
The p_lidtype and p_lid members specify the ID type and ID of one (“left”) set of processes; the p_ridtype and p_rid members 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(). The p_op member specifies the operation to be performed on the two sets of processes to get the set of processes the function is to apply to. The valid values for p_op 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.
Upon successful completion, 0 is return. Otherwise, -1 is returned and errno is set to indicate the error.
The sigsend() and sigsendset() functions will fail if:
The sig argument is not a valid signal number, or the idtype argument is not a valid idtype field.
The sig argument is SIGKILL, idtype is P_PID and id is 1 (proc1).
The effective user of the calling process is not superuser and its real
or effective user ID 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 idtype.
The sigsendset() function will fail if:
The psp argument points to an illegal address.