POSIX says: "If process number 0 is specified, all processes in the current process group shall be signaled."
Add the corresponding line from kill.2 to document this case. Index: kill.1 =================================================================== RCS file: /cvs/src/bin/kill/kill.1,v retrieving revision 1.37 diff -u -p -r1.37 kill.1 --- kill.1 13 Oct 2014 09:27:22 -0000 1.37 +++ kill.1 16 Jan 2015 09:45:46 -0000 @@ -33,7 +33,7 @@ .\" .\" @(#)kill.1 8.2 (Berkeley) 4/28/95 .\" -.Dd $Mdocdate: October 13 2014 $ +.Dd $Mdocdate: January 16 2015 $ .Dt KILL 1 .Os .Sh NAME @@ -96,6 +96,9 @@ of the default .Pp The following PIDs have special meanings: .Bl -tag -width Ds -offset indent +.It 0 +Send the signal to all processes whose group ID is equal to the +process group ID of the sender and for which the process has permission. .It \-1 If superuser, broadcast the signal to all processes; otherwise, broadcast to all processes belonging to the user.
