The "kill -0 $pid" (kill ZERO) option is apparently not to send a signal to some process but to test whether the process is alive. A quick look at the source code of kill(1) shows that if 0 is given as signal number, the kill(2) system call is performed with 0 (simple passthrough). The man page of kill(2) says "If sig is 0, then no signal is sent, but error checking is still performed." --> So, a remark to that effect should be in the kill(1) manpage. Note that the called "kill" will probably rarely be "/bin/kill" but instead the bash-builtin "kill". The bash manpage has the same problem as described.
Fixed in util-linux-ng upstream code. Thanks for your report.
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An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHBA-2008-0751.html