sigvec

Purpose

     Selects enhanced signal facilities.

Syntax

     #include <sys/signal.h>

     int sigvec (sig, invec, outvec)
     int sig;
     struct sigvec *invec, *outvec;

Description

     The sigvec system call allows the user to select standard
     or enhanced signal-handling  facilities.  Like the signal
     system call, it sets the  action to take upon the receipt
     of a signal, but it also sets additional features.

     The sigvec system  call assigns a handler  for a specific
     signal.  If the invec parameter  is nonzero, it points to
     a sigvec  structure that specifies a  handler routine and
     mask  to be  used when  delivering the  specified signal.
     The sigvec structure has the following members:

          int  (*sv_handler) ( );
          int  sv_mask;
          int  sv_onstack;

     If the SIG_STK bit of  sv_onstack is set, then the system
     runs the  handler on  the signal  stack specified  by the
     sigstack system call.   If this bit is not  set, then the
     handler executes on the stack of the interrupted process.
     If the  SIG_STD bit of  sv_onstack is set,  then standard
     signal processing is used.  If  this bit is not set, then
     enhanced signal processing is used.

     The  default action  for a  signal can  be reinstated  by
     setting sv_handler  to SIG_DFL.  If sv_handler  is set to
     SIG_IGN,  then   the  signal  is  ignored,   and  pending
     instances of the signal  are discarded.  See "signal" for
     a detailed description of the default signal actions.

     If  the outvec  parameter is  nonzero, then  the previous
     handling  information for  the  signal is  stored in  the
     sigvec structure pointed to by outvec.

     If the value of the invec parameter is 0 (that is, a NULL
     pointer), then the signal handler information is not set.
     If the value of the outvec  parameter is 0, then the pre-
     vious signal handler information is not reported.

     Once a  signal handler  is assigned, it  remains assigned
     until  another sigvec,  signal,  or exec  system call  is
     made.

     Warning:   The  sigvec system  call  does  not check  the
     validity of  the sv_handler pointer.  If  it &pointsout.,
     then the process receives a  memory fault when the system
     attempts  to  call  the signal  handler.   If  sv_handler
     points  to anything  other  than a  subroutine, then  the
     results are unpredictable.

     The signal-handler subroutine can be declared as follows:

        handler (sig, code, scp)
        int sig, code;
        struct sigcontext *scp;

     The sig parameter is the  signal number.  The code param-
     eter  is  provided  only  for  compatibility  with  other
     UNIX-compatible systems, and its  value is always 0.  The
     scp parameter points to  the sigcontext structure that is
     later used  to restore  the process's  previous execution
     context.    The  sigcontext   structure  is   defined  in
     signal.h.

     Note:   The  sigcontext  structure  contains  fields  for
     saving the values of  the floating-point registers.  On a
     SIGFPE signal,  the values  in all  of the  registers are
     saved.  On all other signals, only the first eight regis-
     ters are saved.

     Refer to "BSD 4.3  library" for additional information on
     the differences between AIX and 4.3BSD signal handling.

Return Value

     Upon successful completion, a value of 0 is returned.  If
     the sigvec system  call fails, a value of  -1 is returned
     and errno is set to indicate the error.

Diagnostics

     The sigvec system call fails and no new signal handler is
     installed if one of the following occurs:

     EFAULT     The invec or outvec parameter &pointsout.

     EINVAL     The  sig  parameter  is  not  a  valid  signal
                number.

     EINVAL     An  attempt was  made  to ignore  or supply  a
                handler for SIGKILL.

Related Information

     In this  book:    "BSD 4.3 library,"  "kill,"  "ptrace,"
     "sigblock,"   "sigpause,"    "sigstack,"    "sigsetmask,"
     "sigvec," and  "setjmp, longjmp."

     The kill command in  AIX Operating System Commands Refer-
     ence.