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The
function sends the signal given by to a process or a group of processes.
may be one of the signals specified in or it may be 0, in which case
error checking is performed but no signal is actually sent. This can be
used to check the validity of For a process to have permission to send
a signal to a process designated by the real or effective user ID of the
receiving process must match that of the sending process or the user must
have appropriate privileges (such as given by a set-user-ID program or the
user is the super-user). A single exception is the signal SIGCONT, which
may always be sent to any descendant of the current process. is sent
to the process whose ID is equal to is sent to all processes whose group
ID is equal to the process group ID of the sender, and for which the process
has permission; this is a variant of If the user has super-user privileges,
the signal is sent to all processes excluding system processes and the
process sending the signal. If the user is not the super user, the signal
is sent to all processes with the same uid as the user excluding the process
sending the signal. No error is returned if any process could be signaled.
For compatibility with System V, if the process number is negative but
not -1, the signal is sent to all processes whose process group ID is equal
to the absolute value of the process number. This is a variant of
Upon successful completion, a value of 0 is returned. Otherwise, a
value of -1 is returned and is set to indicate the error.
will fail
and no signal will be sent if: is not a valid signal number. No process
can be found corresponding to that specified by The process id was given
as 0 but the sending process does not have a process group. The sending
process is not the super-user and its effective user id does not match the
effective user-id of the receiving process. When signaling a process group,
this error is returned if any members of the group could not be signaled.
The function is expected to conform to
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