FPSigaction function

Declaration

function FPSigaction(sig: cint; act: psigactionrec; oact: psigactionrec)
: cint

Description

FPSigaction changes the action to take upon receipt of a signal. Act and Oact are pointers to a SigActionRec record. Sig specifies the signal, and can be any signal except SIGKILL or SIGSTOP.

If Act is non-nil, then the new action for signal Sig is taken from it. If OAct is non-nil, the old action is stored there. Sa_Handler may be SIG_DFL for the default action or SIG_IGN to ignore the signal. Sa_Mask Specifies which signals should be ignored during the execution of the signal handler. Sa_Flags Specifies a series of flags which modify the behaviour of the signal handler. You can 'or' none or more of the following :

SA_NOCLDSTOP

If sig is SIGCHLD do not receive notification when child processes stop.

SA_ONESHOT or SA_RESETHAND

Restore the signal action to the default state once the signal handler has been called.

SA_RESTART

For compatibility with BSD signals.

SA_NOMASK or SA_NODEFER

Do not prevent the signal from being received from within its own signal handler.

Errors

Extended error information can be retrieved using fpGetErrno.

sys_einval

an invalid signal was specified, or it was SIGKILL or SIGSTOP.

sys_efault

Act,OldAct point outside this process address space

sys_eintr

System call was interrupted.

See also

• FpSigProcMask
• FpSigPending
• FpSigSuspend
• FpKill

Example: ex57

Program example57;

{ Program to demonstrate the SigAction function.}

{
do a kill -USR1 pid from another terminal to see what happens.
replace pid with the real pid of this program.
You can get this pid by running 'ps'.
}

uses BaseUnix;

Var
   oa,na : PSigActionRec;

Procedure DoSig(sig : cint);cdecl;

begin
   writeln('Receiving signal: ',sig);
end;

begin
   new(na);
   new(oa);
   na^.sa_Handler:=SigActionHandler(@DoSig);
   fillchar(na^.Sa_Mask,sizeof(na^.sa_mask),#0);
   na^.Sa_Flags:=0;
   {$ifdef Linux}               // Linux specific
     na^.Sa_Restorer:=Nil;
   {$endif}
   if fpSigAction(SigUsr1,na,oa)<>0 then
     begin
     writeln('Error: ',fpgeterrno,'.');
     halt(1);
     end;
   Writeln ('Send USR1 signal or press <ENTER> to exit');
   readln;
end.