@node sntp Invocation
@section Invoking sntp
@pindex sntp
@cindex standard Simple Network Time Protocol client program
@ignore
#
# EDIT THIS FILE WITH CAUTION (invoke-sntp.texi)
#
# It has been AutoGen-ed June 23, 2020 at 02:19:36 AM by AutoGen 5.18.5
# From the definitions sntp-opts.def
# and the template file agtexi-cmd.tpl
@end ignore
@code{sntp}
can be used as an SNTP client to query a NTP or SNTP server and either display
the time or set the local system's time (given suitable privilege). It can be
run as an interactive command or from a
@code{cron}
job.
NTP (the Network Time Protocol) and SNTP (the Simple Network Time Protocol)
are defined and described by RFC 5905.
The default is to write the estimated correct local date and time (i.e. not
UTC) to the standard output in a format like:
@code{'1996-10-15 20:17:25.123 (+0800) +4.567 +/- 0.089 [host] IP sN'}
where the
@code{'(+0800)'}
means that to get to UTC from the reported local time one must
add 8 hours and 0 minutes,
the
@code{'+4.567'}
indicates the local clock is 4.567 seconds behind the correct time
(so 4.567 seconds must be added to the local clock to get it to be correct).
Note that the number of decimals printed for this value will change
based on the reported precision of the server.
@code{'+/- 0.089'}
is the reported
@emph{synchronization} @emph{distance}
(in seconds), which represents the maximum error due to all causes.
If the server does not report valid data needed to calculate the
synchronization distance, this will be reported as
@code{'+/- ?'}.
If the
@emph{host}
is different from the
@emph{IP},
both will be displayed.
Otherwise, only the
@emph{IP}
is displayed.
Finally, the
@emph{stratum}
of the host is reported
and the leap indicator is decoded and displayed.
This section was generated by @strong{AutoGen},
using the @code{agtexi-cmd} template and the option descriptions for the @code{sntp} program.
This software is released under the NTP license, <http://ntp.org/license>.
@menu
* sntp usage:: sntp help/usage (@option{--help})
* sntp ipv4:: ipv4 option (-4)
* sntp ipv6:: ipv6 option (-6)
* sntp authentication:: authentication option (-a)
* sntp broadcast:: broadcast option (-b)
* sntp concurrent:: concurrent option (-c)
* sntp gap:: gap option (-g)
* sntp kod:: kod option (-K)
* sntp keyfile:: keyfile option (-k)
* sntp logfile:: logfile option (-l)
* sntp steplimit:: steplimit option (-M)
* sntp ntpversion:: ntpversion option (-o)
* sntp usereservedport:: usereservedport option (-r)
* sntp timeout:: timeout option (-t)
* sntp wait:: wait option
* sntp config:: presetting/configuring sntp
* sntp exit status:: exit status
* sntp Usage:: Usage
* sntp Authors:: Authors
@end menu
@node sntp usage
@subsection sntp help/usage (@option{--help})
@cindex sntp help
This is the automatically generated usage text for sntp.
The text printed is the same whether selected with the @code{help} option
(@option{--help}) or the @code{more-help} option (@option{--more-help}). @code{more-help} will print
the usage text by passing it through a pager program.
@code{more-help} is disabled on platforms without a working
@code{fork(2)} function. The @code{PAGER} environment variable is
used to select the program, defaulting to @file{more}. Both will exit
with a status code of 0.
@exampleindent 0
@example
sntp - standard Simple Network Time Protocol client program - Ver. 4.2.8p15
Usage: sntp [ -<flag> [<val>] | --<name>[@{=| @}<val>] ]... \
[ hostname-or-IP ...]
Flg Arg Option-Name Description
-4 no ipv4 Force IPv4 DNS name resolution
- prohibits the option 'ipv6'
-6 no ipv6 Force IPv6 DNS name resolution
- prohibits the option 'ipv4'
-a Num authentication Enable authentication with the key auth-keynumber
-b Str broadcast Listen to the address specified for broadcast time sync
- may appear multiple times
-c Str concurrent Concurrently query all IPs returned for host-name
- may appear multiple times
-d no debug-level Increase debug verbosity level
- may appear multiple times
-D Num set-debug-level Set the debug verbosity level
- may appear multiple times
-g Num gap The gap (in milliseconds) between time requests
-K Fil kod KoD history filename
-k Fil keyfile Look in this file for the key specified with -a
-l Fil logfile Log to specified logfile
-M Num steplimit Adjustments less than steplimit msec will be slewed
- it must be in the range:
greater than or equal to 0
-o Num ntpversion Send int as our NTP protocol version
- it must be in the range:
0 to 7
-r no usereservedport Use the NTP Reserved Port (port 123)
-S no step OK to 'step' the time with settimeofday(2)
-s no slew OK to 'slew' the time with adjtime(2)
-t Num timeout The number of seconds to wait for responses
no wait Wait for pending replies (if not setting the time)
- disabled as '--no-wait'
- enabled by default
opt version output version information and exit
-? no help display extended usage information and exit
-! no more-help extended usage information passed thru pager
-> opt save-opts save the option state to a config file
-< Str load-opts load options from a config file
- disabled as '--no-load-opts'
- may appear multiple times
Options are specified by doubled hyphens and their name or by a single
hyphen and the flag character.
The following option preset mechanisms are supported:
- reading file $HOME/.ntprc
- reading file ./.ntprc
- examining environment variables named SNTP_*
Please send bug reports to: <http://bugs.ntp.org, bugs@@ntp.org>
@end example
@exampleindent 4
@node sntp ipv4
@subsection ipv4 option (-4)
@cindex sntp-ipv4
This is the ``force ipv4 dns name resolution'' option.
@noindent
This option has some usage constraints. It:
@itemize @bullet
@item
must not appear in combination with any of the following options:
ipv6.
@end itemize
Force DNS resolution of the following host names on the command line
to the IPv4 namespace.
@node sntp ipv6
@subsection ipv6 option (-6)
@cindex sntp-ipv6
This is the ``force ipv6 dns name resolution'' option.
@noindent
This option has some usage constraints. It:
@itemize @bullet
@item
must not appear in combination with any of the following options:
ipv4.
@end itemize
Force DNS resolution of the following host names on the command line
to the IPv6 namespace.
@node sntp authentication
@subsection authentication option (-a)
@cindex sntp-authentication
This is the ``enable authentication with the key @var{auth-keynumber}'' option.
This option takes a number argument @file{auth-keynumber}.
Enable authentication using the key specified in this option's
argument. The argument of this option is the @option{keyid}, a
number specified in the @option{keyfile} as this key's identifier.
See the @option{keyfile} option (@option{-k}) for more details.
@node sntp broadcast
@subsection broadcast option (-b)
@cindex sntp-broadcast
This is the ``listen to the address specified for broadcast time sync'' option.
This option takes a string argument @file{broadcast-address}.
@noindent
This option has some usage constraints. It:
@itemize @bullet
@item
may appear an unlimited number of times.
@end itemize
If specified @code{sntp} will listen to the specified address
for NTP broadcasts. The default maximum wait time
can (and probably should) be modified with @option{-t}.
@node sntp concurrent
@subsection concurrent option (-c)
@cindex sntp-concurrent
This is the ``concurrently query all ips returned for host-name'' option.
This option takes a string argument @file{host-name}.
@noindent
This option has some usage constraints. It:
@itemize @bullet
@item
may appear an unlimited number of times.
@end itemize
Requests from an NTP "client" to a "server" should never be sent
more rapidly than one every 2 seconds. By default, any IPs returned
as part of a DNS lookup are assumed to be for a single instance of
@code{ntpd}, and therefore @code{sntp} will send queries to these IPs
one after another, with a 2-second gap in between each query.
The @option{-c} or @option{--concurrent} flag says that any IPs
returned for the DNS lookup of the supplied host-name are on
different machines, so we can send concurrent queries.
@node sntp gap
@subsection gap option (-g)
@cindex sntp-gap
This is the ``the gap (in milliseconds) between time requests'' option.
This option takes a number argument @file{milliseconds}.
Since we're only going to use the first valid response we get and
there is benefit to specifying a good number of servers to query,
separate the queries we send out by the specified number of
milliseconds.
@node sntp kod
@subsection kod option (-K)
@cindex sntp-kod
This is the ``kod history filename'' option.
This option takes a file argument @file{file-name}.
Specifies the filename to be used for the persistent history of KoD
responses received from servers. If the file does not exist, a
warning message will be displayed. The file will not be created.
@node sntp keyfile
@subsection keyfile option (-k)
@cindex sntp-keyfile
This is the ``look in this file for the key specified with @option{-a}'' option.
This option takes a file argument @file{file-name}.
This option specifies the keyfile.
@code{sntp} will search for the key specified with @option{-a}
@file{keyno} in this file. See @command{ntp.keys(5)} for more
information.
@node sntp logfile
@subsection logfile option (-l)
@cindex sntp-logfile
This is the ``log to specified logfile'' option.
This option takes a file argument @file{file-name}.
This option causes the client to write log messages to the specified
@file{logfile}.
@node sntp steplimit
@subsection steplimit option (-M)
@cindex sntp-steplimit
This is the ``adjustments less than @var{steplimit} msec will be slewed'' option.
This option takes a number argument.
If the time adjustment is less than @file{steplimit} milliseconds,
slew the amount using @command{adjtime(2)}. Otherwise, step the
correction using @command{settimeofday(2)}. The default value is 0,
which means all adjustments will be stepped. This is a feature, as
different situations demand different values.
@node sntp ntpversion
@subsection ntpversion option (-o)
@cindex sntp-ntpversion
This is the ``send @var{int} as our ntp protocol version'' option.
This option takes a number argument.
When sending requests to a remote server, tell them we are running
NTP protocol version @file{ntpversion} .
@node sntp usereservedport
@subsection usereservedport option (-r)
@cindex sntp-usereservedport
This is the ``use the ntp reserved port (port 123)'' option.
Use port 123, which is reserved for NTP, for our network
communications.
@node sntp timeout
@subsection timeout option (-t)
@cindex sntp-timeout
This is the ``the number of seconds to wait for responses'' option.
This option takes a number argument @file{seconds}.
When waiting for a reply, @code{sntp} will wait the number
of seconds specified before giving up. The default should be
more than enough for a unicast response. If @code{sntp} is
only waiting for a broadcast response a longer timeout is
likely needed.
@node sntp wait
@subsection wait option
@cindex sntp-wait
This is the ``wait for pending replies (if not setting the time)'' option.
@noindent
This option has some usage constraints. It:
@itemize @bullet
@item
can be disabled with --no-wait.
@item
It is enabled by default.
@end itemize
If we are not setting the time, wait for all pending responses.
@node sntp config
@subsection presetting/configuring sntp
Any option that is not marked as @i{not presettable} may be preset by
loading values from configuration ("rc" or "ini") files, and values from environment variables named @code{SNTP} and @code{SNTP_<OPTION_NAME>}. @code{<OPTION_NAME>} must be one of
the options listed above in upper case and segmented with underscores.
The @code{SNTP} variable will be tokenized and parsed like
the command line. The remaining variables are tested for existence and their
values are treated like option arguments.
@noindent
@code{libopts} will search in 2 places for configuration files:
@itemize @bullet
@item
$HOME
@item
$PWD
@end itemize
The environment variables @code{HOME}, and @code{PWD}
are expanded and replaced when @file{sntp} runs.
For any of these that are plain files, they are simply processed.
For any that are directories, then a file named @file{.ntprc} is searched for
within that directory and processed.
Configuration files may be in a wide variety of formats.
The basic format is an option name followed by a value (argument) on the
same line. Values may be separated from the option name with a colon,
equal sign or simply white space. Values may be continued across multiple
lines by escaping the newline with a backslash.
Multiple programs may also share the same initialization file.
Common options are collected at the top, followed by program specific
segments. The segments are separated by lines like:
@example
[SNTP]
@end example
@noindent
or by
@example
<?program sntp>
@end example
@noindent
Do not mix these styles within one configuration file.
Compound values and carefully constructed string values may also be
specified using XML syntax:
@example
<option-name>
<sub-opt>...<...>...</sub-opt>
</option-name>
@end example
@noindent
yielding an @code{option-name.sub-opt} string value of
@example
"...<...>..."
@end example
@code{AutoOpts} does not track suboptions. You simply note that it is a
hierarchicly valued option. @code{AutoOpts} does provide a means for searching
the associated name/value pair list (see: optionFindValue).
The command line options relating to configuration and/or usage help are:
@subsubheading version (-)
Print the program version to standard out, optionally with licensing
information, then exit 0. The optional argument specifies how much licensing
detail to provide. The default is to print just the version. The licensing infomation may be selected with an option argument.
Only the first letter of the argument is examined:
@table @samp
@item version
Only print the version. This is the default.
@item copyright
Name the copyright usage licensing terms.
@item verbose
Print the full copyright usage licensing terms.
@end table
@node sntp exit status
@subsection sntp exit status
One of the following exit values will be returned:
@table @samp
@item 0 (EXIT_SUCCESS)
Successful program execution.
@item 1 (EXIT_FAILURE)
The operation failed or the command syntax was not valid.
@item 66 (EX_NOINPUT)
A specified configuration file could not be loaded.
@item 70 (EX_SOFTWARE)
libopts had an internal operational error. Please report
it to autogen-users@@lists.sourceforge.net. Thank you.
@end table
@node sntp Usage
@subsection sntp Usage
@node sntp Authors
@subsection sntp Authors