I think there's a bug in ping - netkit-base-0.10-31; RedHat
6.0:

When I send a single ping to a machine that's shut down,
ping keeps on trying after the first failure,
despite using -c 1 .
That means it's impossible to test whether a machine is
alive, eg
    ping -c 1 datix
    if [ $? -eq 0 ]; then
        echo "It's alive"
    else
        echo "No ping response"
    fi

because ping *never* returns!
Ping reports "Destination Host Unreachable" over and over...

    ping -c 1 somemachine
works as expected if "somemachine" responds (returns 0)
or "somemachine" doesn't exist (returns 1)
but if "somemachine" exists but is turned off, ping tries
forever.

Ping(1) clearly states:
  If ping does not receive any reply packets at all it will
exit with code
  1.  On error it exits with code 2. Otherwise it exits with
code 0. This
  makes it possible to use the exit code to see if a host is
alive or not.


I've written a little script to work around this bug, but
I'm not happy having to do so.  Can ping be fixed to agree
with its man page?

**************   /usr/local/bin/pingtest   *************

#!/bin/sh
#   Silently pings $1 to see if it's alive,
#   with protection against hangs if it's not (ping has a
bug)
#   Returns 0 if alive; else 1

nohup ping -c1 $1 > /dev/null 2>&1 &
sleep 2
PINGPID=` ps | grep "ping " | grep -v grep | cut -d " " -f1
`
if [ -n "$PINGPID" ]; then
#    echo "ping $1 is hung; kill $PINGPID"
    kill $PINGPID
    exit 1
else
#    echo ping $1 succeeded
    exit 0
fi

**************   END /usr/local/bin/pingtest   *************




This must be a bug.