"><IMG
 WIDTH="76" HEIGHT="15" ALIGN="BOTTOM" BORDER="0"
 SRC="manual-img38.png"
 ALT="$which=0$"></SPAN>, process group  identifier  for  <SPAN CLASS="MATH"><IMG
 WIDTH="76" HEIGHT="15" ALIGN="BOTTOM" BORDER="0"
 SRC="manual-img39.png"
 ALT="$which=1$"></SPAN>,
and  a  user ID for <SPAN CLASS="MATH"><IMG
 WIDTH="76" HEIGHT="15" ALIGN="BOTTOM" BORDER="0"
 SRC="manual-img40.png"
 ALT="$which=2$"></SPAN>.
A zero value of who denotes
the current process, process group, or user.
To lower the priority  (nice val