ping.8

<B>Digital的Unix操作系统VAX 4.2源码</B>

.TH ping 8 
.SH Name
ping \- send ICMP ECHO_REQUEST packets to network hosts
.SH Syntax
.B /etc/ping
[ \fIoptions\fR ]
.I host
[
.I datasize
[
.I npackets
]]
.SH Description
.NXR "ping command"
.NXR "ICMP ECHO_REQUEST"
The DARPA Internet is a large and complex 
network of hardware connected together by gateways.
The 
.PN ping
command utilizes the
ICMP protocol's mandatory ECHO_REQUEST datagram to elicit an
ICMP ECHO_RESPONSE from a host or gateway.
ECHO_REQUEST datagrams (pings) have an IP and ICMP header,
followed by a \fBstruct timeval\fR, and then an arbitrary number
of pad bytes used to fill out the packet.
The length of the default datagram 64 bytes, but this may be changed
using the command-line option.
.PP
Typing ``ping \fIhost\fR'' without any options will either report ``\fIhost\fR
is alive'' or ``no answer from \fIhost\fR''.
To get more statistics use the 
.B \-l
option or one of the other options.
.PP
When using 
.PN ping
for fault isolation,
it should first be run on the local
host to verify that the local network interface is up and
running.
Then, hosts and gateways further and further away
should be pinged.
The
.PN ping
command with options sends one datagram per second and
prints one line of output for every ECHO_RESPONSE returned.
No output is produced if there is no response.
If an optional
.I npackets
is given, only that number of requests is sent.
Round-trip times and packet loss statistics are computed.
When all responses have been received or the program times out with
.I npackets
specified,
or if the program is terminated with a SIGINT, a brief
summary is displayed.
.SH Options
.IP \fB-d\fR 5
Turns on SO_DEBUG flag on the socket.
.IP \fB-l\fR 5
Gives more statistics than if 
.PN ping
is used without options.  Long output. 
.IP \fB-r\fR 5
Bypasses the normal routing tables and sends directly to a host on an attached
network.
If the host is not on a directly-attached network,
an error is returned.
This option can be used to ping a local host through an interface
that has no route through it.  For example, after the interface was dropped by
.MS routed 8c .
.IP \fB-v\fR 5
Lists ICMP packets other than ECHO RESPONSE that are received. Verbose output.
.SH Restrictions
This program is intended for use in network testing, measurement,
and management.
It should be used primarily for manual fault isolation.
Because of the load it could impose on the network,
it is unwise to use
.PN ping
during normal operations or from automated scripts.
.SH See Also
netstat(1), ifconfig(8c)