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<html lang="en">
<head>
<title>Sntp User's Manual</title>
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<h1 class="settitle">Sntp User's Manual</h1>
<div class="node">
<p><hr>
<a name="Top"></a>Next: <a rel="next" accesskey="n" href="#sntp-Description">sntp Description</a>,
Previous: <a rel="previous" accesskey="p" href="#dir">(dir)</a>,
Up: <a rel="up" accesskey="u" href="#dir">(dir)</a>
<br>
</div>
<h2 class="unnumbered">Simple Network Time Protocol User Manual</h2>
<p>This document describes the use of the NTP Project's <code>sntp</code> program,
that can be used to query a Network Time Protocol (NTP) server and
display the time offset of the system clock relative to the server
clock. Run as root, it can correct the system clock to this offset as
well. It can be run as an interactive command or from a cron job.
<p>This document applies to version 4.2.8p3 of <code>sntp</code>.
<p>The program implements the SNTP protocol as defined by RFC 5905, the NTPv4
IETF specification.
<div class="shortcontents">
<h2>Short Contents</h2>
<ul>
<a href="#Top">Simple Network Time Protocol User Manual</a>
</ul>
</div>
<ul class="menu">
<li><a accesskey="1" href="#sntp-Description">sntp Description</a>: Description
<li><a accesskey="2" href="#sntp-Invocation">sntp Invocation</a>: Invoking sntp
<li><a accesskey="3" href="#Usage">Usage</a>: Usage
</ul>
<div class="node">
<p><hr>
<a name="sntp-Description"></a>
<br>
</div>
<!-- node-name, next, previous, up -->
<h3 class="section">Description</h3>
<p>By default, <code>sntp</code> writes the local data and time (i.e., not UTC) to the
standard output in the format:
<pre class="example"> 1996-10-15 20:17:25.123 (+0800) +4.567 +/- 0.089 secs
</pre>
<p>where
YYYY-MM-DD HH:MM:SS.SUBSEC is the local date and time,
(+0800) is the local timezone adjustment (so we would add 8 hours and 0 minutes to convert the reported local time to UTC),
and
the +4.567 +/- 0.089 secs indicates the time offset and
error bound of the system clock relative to the server clock.
<div class="node">
<p><hr>
<a name="sntp-Invocation"></a>
<br>
</div>
<h3 class="section">Invoking sntp</h3>
<p><a name="index-sntp-1"></a><a name="index-standard-Simple-Network-Time-Protocol-client-program-2"></a>
<p><code>sntp</code>
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</code>
job.
<p>NTP (the Network Time Protocol) and SNTP (the Simple Network Time Protocol)
are defined and described by RFC 5905.
<p>The default is to write the estimated correct local date and time (i.e. not
UTC) to the standard output in a format like:
<p><code>'1996-10-15 20:17:25.123 (+0800) +4.567 +/- 0.089 [host] IP sN'</code>
<p>where the
<code>'(+0800)'</code>
means that to get to UTC from the reported local time one must
add 8 hours and 0 minutes,
the
<code>'+4.567'</code>
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'</code>
is the reported
<em>synchronization</em> <em>distance</em>
(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>'+/- ?'</code>.
If the
<em>host</em>
is different from the
<em>IP</em>,
both will be displayed.
Otherwise, only the
<em>IP</em>
is displayed.
Finally, the
<em>stratum</em>
of the host is reported
and the leap indicator is decoded and displayed.
<p>This section was generated by <strong>AutoGen</strong>,
using the <code>agtexi-cmd</code> template and the option descriptions for the <code>sntp</code> program.
This software is released under the NTP license, <http://ntp.org/license>.
<ul class="menu">
<li><a accesskey="1" href="#sntp-usage">sntp usage</a>: sntp help/usage (<span class="option">--help</span>)
<li><a accesskey="2" href="#sntp-ipv4">sntp ipv4</a>: ipv4 option (-4)
<li><a accesskey="3" href="#sntp-ipv6">sntp ipv6</a>: ipv6 option (-6)
<li><a accesskey="4" href="#sntp-authentication">sntp authentication</a>: authentication option (-a)
<li><a accesskey="5" href="#sntp-broadcast">sntp broadcast</a>: broadcast option (-b)
<li><a accesskey="6" href="#sntp-concurrent">sntp concurrent</a>: concurrent option (-c)
<li><a accesskey="7" href="#sntp-gap">sntp gap</a>: gap option (-g)
<li><a accesskey="8" href="#sntp-kod">sntp kod</a>: kod option (-K)
<li><a accesskey="9" href="#sntp-keyfile">sntp keyfile</a>: keyfile option (-k)
<li><a href="#sntp-logfile">sntp logfile</a>: logfile option (-l)
<li><a href="#sntp-steplimit">sntp steplimit</a>: steplimit option (-M)
<li><a href="#sntp-ntpversion">sntp ntpversion</a>: ntpversion option (-o)
<li><a href="#sntp-usereservedport">sntp usereservedport</a>: usereservedport option (-r)
<li><a href="#sntp-timeout">sntp timeout</a>: timeout option (-t)
<li><a href="#sntp-wait">sntp wait</a>: wait option
<li><a href="#sntp-config">sntp config</a>: presetting/configuring sntp
<li><a href="#sntp-exit-status">sntp exit status</a>: exit status
<li><a href="#sntp-Usage">sntp Usage</a>: Usage
<li><a href="#sntp-Authors">sntp Authors</a>: Authors
</ul>
<div class="node">
<p><hr>
<a name="sntp-usage"></a>Next: <a rel="next" accesskey="n" href="#sntp-ipv4">sntp ipv4</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">sntp help/usage (<span class="option">--help</span>)</h4>
<p><a name="index-sntp-help-3"></a>
This is the automatically generated usage text for sntp.
<p>The text printed is the same whether selected with the <code>help</code> option
(<span class="option">--help</span>) or the <code>more-help</code> option (<span class="option">--more-help</span>). <code>more-help</code> will print
the usage text by passing it through a pager program.
<code>more-help</code> is disabled on platforms without a working
<code>fork(2)</code> function. The <code>PAGER</code> environment variable is
used to select the program, defaulting to <span class="file">more</span>. Both will exit
with a status code of 0.
<pre class="example">sntp - standard Simple Network Time Protocol client program - Ver. 4.2.8p3
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>
</pre>
<div class="node">
<p><hr>
<a name="sntp-ipv4"></a>Next: <a rel="next" accesskey="n" href="#sntp-ipv6">sntp ipv6</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-usage">sntp usage</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">ipv4 option (-4)</h4>
<p><a name="index-sntp_002dipv4-4"></a>
This is the “force ipv4 dns name resolution” option.
<p class="noindent">This option has some usage constraints. It:
<ul>
<li>must not appear in combination with any of the following options:
ipv6.
</ul>
<p>Force DNS resolution of the following host names on the command line
to the IPv4 namespace.
<div class="node">
<p><hr>
<a name="sntp-ipv6"></a>Next: <a rel="next" accesskey="n" href="#sntp-authentication">sntp authentication</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-ipv4">sntp ipv4</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">ipv6 option (-6)</h4>
<p><a name="index-sntp_002dipv6-5"></a>
This is the “force ipv6 dns name resolution” option.
<p class="noindent">This option has some usage constraints. It:
<ul>
<li>must not appear in combination with any of the following options:
ipv4.
</ul>
<p>Force DNS resolution of the following host names on the command line
to the IPv6 namespace.
<div class="node">
<p><hr>
<a name="sntp-authentication"></a>Next: <a rel="next" accesskey="n" href="#sntp-broadcast">sntp broadcast</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-ipv6">sntp ipv6</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">authentication option (-a)</h4>
<p><a name="index-sntp_002dauthentication-6"></a>
This is the “enable authentication with the key <var>auth-keynumber</var>” option.
This option takes a number argument <span class="file">auth-keynumber</span>.
Enable authentication using the key specified in this option's
argument. The argument of this option is the <span class="option">keyid</span>, a
number specified in the <span class="option">keyfile</span> as this key's identifier.
See the <span class="option">keyfile</span> option (<span class="option">-k</span>) for more details.
<div class="node">
<p><hr>
<a name="sntp-broadcast"></a>Next: <a rel="next" accesskey="n" href="#sntp-concurrent">sntp concurrent</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-authentication">sntp authentication</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">broadcast option (-b)</h4>
<p><a name="index-sntp_002dbroadcast-7"></a>
This is the “listen to the address specified for broadcast time sync” option.
This option takes a string argument <span class="file">broadcast-address</span>.
<p class="noindent">This option has some usage constraints. It:
<ul>
<li>may appear an unlimited number of times.
</ul>
<p>If specified <code>sntp</code> will listen to the specified address
for NTP broadcasts. The default maximum wait time
can (and probably should) be modified with <span class="option">-t</span>.
<div class="node">
<p><hr>
<a name="sntp-concurrent"></a>Next: <a rel="next" accesskey="n" href="#sntp-gap">sntp gap</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-broadcast">sntp broadcast</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">concurrent option (-c)</h4>
<p><a name="index-sntp_002dconcurrent-8"></a>
This is the “concurrently query all ips returned for host-name” option.
This option takes a string argument <span class="file">host-name</span>.
<p class="noindent">This option has some usage constraints. It:
<ul>
<li>may appear an unlimited number of times.
</ul>
<p>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</code>, and therefore <code>sntp</code> will send queries to these IPs
one after another, with a 2-second gap in between each query.
<p>The <span class="option">-c</span> or <span class="option">--concurrent</span> 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.
<div class="node">
<p><hr>
<a name="sntp-gap"></a>Next: <a rel="next" accesskey="n" href="#sntp-kod">sntp kod</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-concurrent">sntp concurrent</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">gap option (-g)</h4>
<p><a name="index-sntp_002dgap-9"></a>
This is the “the gap (in milliseconds) between time requests” option.
This option takes a number argument <span class="file">milliseconds</span>.
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.
<div class="node">
<p><hr>
<a name="sntp-kod"></a>Next: <a rel="next" accesskey="n" href="#sntp-keyfile">sntp keyfile</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-gap">sntp gap</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">kod option (-K)</h4>
<p><a name="index-sntp_002dkod-10"></a>
This is the “kod history filename” option.
This option takes a file argument <span class="file">file-name</span>.
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.
<div class="node">
<p><hr>
<a name="sntp-keyfile"></a>Next: <a rel="next" accesskey="n" href="#sntp-logfile">sntp logfile</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-kod">sntp kod</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">keyfile option (-k)</h4>
<p><a name="index-sntp_002dkeyfile-11"></a>
This is the “look in this file for the key specified with <span class="option">-a</span>” option.
This option takes a file argument <span class="file">file-name</span>.
This option specifies the keyfile.
<code>sntp</code> will search for the key specified with <span class="option">-a</span>
<span class="file">keyno</span> in this file. See <span class="command">ntp.keys(5)</span> for more
information.
<div class="node">
<p><hr>
<a name="sntp-logfile"></a>Next: <a rel="next" accesskey="n" href="#sntp-steplimit">sntp steplimit</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-keyfile">sntp keyfile</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">logfile option (-l)</h4>
<p><a name="index-sntp_002dlogfile-12"></a>
This is the “log to specified logfile” option.
This option takes a file argument <span class="file">file-name</span>.
This option causes the client to write log messages to the specified
<span class="file">logfile</span>.
<div class="node">
<p><hr>
<a name="sntp-steplimit"></a>Next: <a rel="next" accesskey="n" href="#sntp-ntpversion">sntp ntpversion</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-logfile">sntp logfile</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">steplimit option (-M)</h4>
<p><a name="index-sntp_002dsteplimit-13"></a>
This is the “adjustments less than <var>steplimit</var> msec will be slewed” option.
This option takes a number argument.
If the time adjustment is less than <span class="file">steplimit</span> milliseconds,
slew the amount using <span class="command">adjtime(2)</span>. Otherwise, step the
correction using <span class="command">settimeofday(2)</span>. The default value is 0,
which means all adjustments will be stepped. This is a feature, as
different situations demand different values.
<div class="node">
<p><hr>
<a name="sntp-ntpversion"></a>Next: <a rel="next" accesskey="n" href="#sntp-usereservedport">sntp usereservedport</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-steplimit">sntp steplimit</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">ntpversion option (-o)</h4>
<p><a name="index-sntp_002dntpversion-14"></a>
This is the “send <var>int</var> 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 <span class="file">ntpversion</span> .
<div class="node">
<p><hr>
<a name="sntp-usereservedport"></a>Next: <a rel="next" accesskey="n" href="#sntp-timeout">sntp timeout</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-ntpversion">sntp ntpversion</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">usereservedport option (-r)</h4>
<p><a name="index-sntp_002dusereservedport-15"></a>
This is the “use the ntp reserved port (port 123)” option.
Use port 123, which is reserved for NTP, for our network
communications.
<div class="node">
<p><hr>
<a name="sntp-timeout"></a>Next: <a rel="next" accesskey="n" href="#sntp-wait">sntp wait</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-usereservedport">sntp usereservedport</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">timeout option (-t)</h4>
<p><a name="index-sntp_002dtimeout-16"></a>
This is the “the number of seconds to wait for responses” option.
This option takes a number argument <span class="file">seconds</span>.
When waiting for a reply, <code>sntp</code> will wait the number
of seconds specified before giving up. The default should be
more than enough for a unicast response. If <code>sntp</code> is
only waiting for a broadcast response a longer timeout is
likely needed.
<div class="node">
<p><hr>
<a name="sntp-wait"></a>Next: <a rel="next" accesskey="n" href="#sntp-config">sntp config</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-timeout">sntp timeout</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">wait option</h4>
<p><a name="index-sntp_002dwait-17"></a>
This is the “wait for pending replies (if not setting the time)” option.
<p class="noindent">This option has some usage constraints. It:
<ul>
<li>can be disabled with –no-wait.
<li>It is enabled by default.
</ul>
<p>If we are not setting the time, wait for all pending responses.
<div class="node">
<p><hr>
<a name="sntp-config"></a>Next: <a rel="next" accesskey="n" href="#sntp-exit-status">sntp exit status</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-wait">sntp wait</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">presetting/configuring sntp</h4>
<p>Any option that is not marked as <i>not presettable</i> may be preset by
loading values from configuration ("rc" or "ini") files, and values from environment variables named <code>SNTP</code> and <code>SNTP_<OPTION_NAME></code>. <code><OPTION_NAME></code> must be one of
the options listed above in upper case and segmented with underscores.
The <code>SNTP</code> 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.
<p class="noindent"><code>libopts</code> will search in 2 places for configuration files:
<ul>
<li>$HOME
<li>$PWD
</ul>
The environment variables <code>HOME</code>, and <code>PWD</code>
are expanded and replaced when <span class="file">sntp</span> runs.
For any of these that are plain files, they are simply processed.
For any that are directories, then a file named <span class="file">.ntprc</span> is searched for
within that directory and processed.
<p>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.
<p>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:
<pre class="example"> [SNTP]
</pre>
<p class="noindent">or by
<pre class="example"> <?program sntp>
</pre>
<p class="noindent">Do not mix these styles within one configuration file.
<p>Compound values and carefully constructed string values may also be
specified using XML syntax:
<pre class="example"> <option-name>
<sub-opt>...&lt;...&gt;...</sub-opt>
</option-name>
</pre>
<p class="noindent">yielding an <code>option-name.sub-opt</code> string value of
<pre class="example"> "...<...>..."
</pre>
<p><code>AutoOpts</code> does not track suboptions. You simply note that it is a
hierarchicly valued option. <code>AutoOpts</code> does provide a means for searching
the associated name/value pair list (see: optionFindValue).
<p>The command line options relating to configuration and/or usage help are:
<h5 class="subsubheading">version (-)</h5>
<p>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:
<dl>
<dt><span class="samp">version</span><dd>Only print the version. This is the default.
<br><dt><span class="samp">copyright</span><dd>Name the copyright usage licensing terms.
<br><dt><span class="samp">verbose</span><dd>Print the full copyright usage licensing terms.
</dl>
<div class="node">
<p><hr>
<a name="sntp-exit-status"></a>Next: <a rel="next" accesskey="n" href="#sntp-Usage">sntp Usage</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-config">sntp config</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">sntp exit status</h4>
<p>One of the following exit values will be returned:
<dl>
<dt><span class="samp">0 (EXIT_SUCCESS)</span><dd>Successful program execution.
<br><dt><span class="samp">1 (EXIT_FAILURE)</span><dd>The operation failed or the command syntax was not valid.
<br><dt><span class="samp">66 (EX_NOINPUT)</span><dd>A specified configuration file could not be loaded.
<br><dt><span class="samp">70 (EX_SOFTWARE)</span><dd>libopts had an internal operational error. Please report
it to autogen-users@lists.sourceforge.net. Thank you.
</dl>
<div class="node">
<p><hr>
<a name="sntp-Usage"></a>Next: <a rel="next" accesskey="n" href="#sntp-Authors">sntp Authors</a>,
Previous: <a rel="previous" accesskey="p" href="#sntp-exit-status">sntp exit status</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">sntp Usage</h4>
<div class="node">
<p><hr>
<a name="sntp-Authors"></a>Previous: <a rel="previous" accesskey="p" href="#sntp-Usage">sntp Usage</a>,
Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a>
<br>
</div>
<h4 class="subsection">sntp Authors</h4>
<div class="node">
<p><hr>
<a name="Usage"></a>
<br>
</div>
<!-- node-name, next, previous, up -->
<h3 class="section">Usage</h3>
<p>The simplest use of this program is as an unprivileged command to
check the current time, offset, and error in the local clock.
For example:
<pre class="example"> sntp ntpserver.somewhere
</pre>
<p>With suitable privilege, it can be run as a command or in a
<code>crom</code> job to reset the local clock from a reliable server, like
the <code>ntpdate</code> and <code>rdate</code> commands.
For example:
<pre class="example"> sntp -a ntpserver.somewhere
</pre>
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