31 The
  32 .Fn Psignal
  33 function sets the signal tracing flag for the process handle
  34 .Fa P .
  35 If
  36 .Fa stop
  37 is
  38 .Sy non-zero
  39 it causes the process handle to stop threads that encounter the signal
  40 .Fa which .
  41 If
  42 .Fa stop
  43 is
  44 .Sy zero ,
  45 then it disables tracing for the signal
  46 .Fa which .
  47 .Pp
  48 The signal constants, representing valid values for
  49 .Fa which ,
  50 can be found in
  51 .Xr signal.h 3HEAD.
  52 The signal
  53 .Dv SIGKILL
  54 may not be stopped.
  55 .Pp
  56 Note, only active processes may have their signal tracing flags updated.
  57 Process handles that refer to core files, zombie processes, and files do
  58 not have signal tracing flags.
  59 Calling this function on them is an error.
  60 .Sh RETURN VALUES
  61 Upon successful completion, the
  62 .Fn Psignal
  63 function returns the previous disposition of the signal
  64 .Fa which .
  65 It returns
  66 .Sy 1
  67 if it was set and
  68 .Sy 0
  69 if not.
  70 Otherwise,
  71 .Sy -1

  31 The
  32 .Fn Psignal
  33 function sets the signal tracing flag for the process handle
  34 .Fa P .
  35 If
  36 .Fa stop
  37 is
  38 .Sy non-zero
  39 it causes the process handle to stop threads that encounter the signal
  40 .Fa which .
  41 If
  42 .Fa stop
  43 is
  44 .Sy zero ,
  45 then it disables tracing for the signal
  46 .Fa which .
  47 .Pp
  48 The signal constants, representing valid values for
  49 .Fa which ,
  50 can be found in
  51 .Xr signal.h 3HEAD .
  52 The signal
  53 .Dv SIGKILL
  54 may not be stopped.
  55 .Pp
  56 Note, only active processes may have their signal tracing flags updated.
  57 Process handles that refer to core files, zombie processes, and files do
  58 not have signal tracing flags.
  59 Calling this function on them is an error.
  60 .Sh RETURN VALUES
  61 Upon successful completion, the
  62 .Fn Psignal
  63 function returns the previous disposition of the signal
  64 .Fa which .
  65 It returns
  66 .Sy 1
  67 if it was set and
  68 .Sy 0
  69 if not.
  70 Otherwise,
  71 .Sy -1