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     47 <h1 class="settitle" align="center">Sntp User&rsquo;s Manual</h1>
     48 
     49 
     50 
     51 
     52 
     53 <a name="Top"></a>
     54 <div class="header">
     55 <p>
     56 Next: <a href="#sntp-Description" accesskey="n" rel="next">sntp Description</a>, Previous: <a href="dir.html#Top" accesskey="p" rel="prev">(dir)</a>, Up: <a href="dir.html#Top" accesskey="u" rel="up">(dir)</a> &nbsp; </p>
     57 </div>
     58 <a name="Simple-Network-Time-Protocol-User-Manual"></a>
     59 <h1 class="top">Simple Network Time Protocol User Manual</h1>
     60 
     61 <p>This document describes the use of the NTP Project&rsquo;s <code>sntp</code> program,
     62 that can be used to query a Network Time Protocol (NTP) server and
     63 display the time offset of the system clock relative to the server
     64 clock.  Run as root, it can correct the system clock to this offset as
     65 well.  It can be run as an interactive command or from a cron job.
     66 </p>
     67 <p>This document applies to version 4.2.8p14 of <code>sntp</code>.
     68 </p>
     69 <p>The program implements the SNTP protocol as defined by RFC 5905, the NTPv4
     70 IETF specification.
     71 </p>
     72 <a name="SEC_Overview"></a>
     73 <h2 class="shortcontents-heading">Short Table of Contents</h2>
     74 
     75 <div class="shortcontents">
     76 <ul class="no-bullet">
     77 <li><a name="stoc-Description" href="#toc-Description">1 Description</a></li>
     78 </ul>
     79 </div>
     80 
     81 
     82 <table class="menu" border="0" cellspacing="0">
     83 <tr><td align="left" valign="top">&bull; <a href="#sntp-Description" accesskey="1">sntp Description</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Description
     84 </td></tr>
     85 <tr><td align="left" valign="top">&bull; <a href="#sntp-Invocation" accesskey="2">sntp Invocation</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Invoking sntp
     86 </td></tr>
     87 <tr><td align="left" valign="top">&bull; <a href="#Usage" accesskey="3">Usage</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Usage
     88 </td></tr>
     89 </table>
     90 
     91 <hr>
     92 <a name="sntp-Description"></a>
     93 <div class="header">
     94 <p>
     95 Next: <a href="#sntp-Invocation" accesskey="n" rel="next">sntp Invocation</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; </p>
     96 </div>
     97 <a name="Description"></a>
     98 <h2 class="chapter">1 Description</h2>
     99 
    100 <p>By default, <code>sntp</code> writes the local data and time (i.e., not UTC) to the
    101 standard output in the format:
    102 </p>
    103 <div class="example">
    104 <pre class="example">1996-10-15 20:17:25.123 (+0800) +4.567 +/- 0.089 secs
    105 </pre></div>
    106 
    107 <p>where
    108 YYYY-MM-DD HH:MM:SS.SUBSEC is the local date and time,
    109 (+0800) is the local timezone adjustment (so we would add 8 hours and 0 minutes to convert the reported local time to UTC),
    110 and
    111 the +4.567 +/- 0.089 secs indicates the time offset and
    112 error bound of the system clock relative to the server clock.
    113 </p>
    114 <table class="menu" border="0" cellspacing="0">
    115 <tr><td align="left" valign="top">&bull; <a href="#sntp-Invocation" accesskey="1">sntp Invocation</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
    116 </td></tr>
    117 <tr><td align="left" valign="top">&bull; <a href="#Usage" accesskey="2">Usage</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
    118 </td></tr>
    119 </table>
    120 
    121 <hr>
    122 <a name="sntp-Invocation"></a>
    123 <div class="header">
    124 <p>
    125 Next: <a href="#Usage" accesskey="n" rel="next">Usage</a>, Previous: <a href="#sntp-Description" accesskey="p" rel="prev">sntp Description</a>, Up: <a href="#sntp-Description" accesskey="u" rel="up">sntp Description</a> &nbsp; </p>
    126 </div>
    127 <a name="Invoking-sntp"></a>
    128 <h3 class="section">1.1 Invoking sntp</h3>
    129 <a name="index-sntp"></a>
    130 <a name="index-standard-Simple-Network-Time-Protocol-client-program"></a>
    131 
    132 
    133 
    134 <p><code>sntp</code>
    135 can be used as an SNTP client to query a NTP or SNTP server and either display
    136 the time or set the local system&rsquo;s time (given suitable privilege).  It can be
    137 run as an interactive command or from a
    138 <code>cron</code>
    139 job.
    140 </p>
    141 <p>NTP (the Network Time Protocol) and SNTP (the Simple Network Time Protocol)
    142 are defined and described by RFC 5905.
    143 </p>
    144 
    145 <p>The default is to write the estimated correct local date and time (i.e. not
    146 UTC) to the standard output in a format like:
    147 </p>
    148 <p><code>'1996-10-15 20:17:25.123 (+0800) +4.567 +/- 0.089 [host] IP sN'</code>
    149 </p>
    150 <p>where the
    151 <code>'(+0800)'</code>
    152 means that to get to UTC from the reported local time one must
    153 add 8 hours and 0 minutes,
    154 the
    155 <code>'+4.567'</code>
    156 indicates the local clock is 4.567 seconds behind the correct time
    157 (so 4.567 seconds must be added to the local clock to get it to be correct).
    158 Note that the number of decimals printed for this value will change
    159 based on the reported precision of the server.
    160 <code>'+/- 0.089'</code>
    161 is the reported
    162 <em>synchronization</em> <em>distance</em>
    163 (in seconds), which represents the maximum error due to all causes.
    164 If the server does not report valid data needed to calculate the
    165 synchronization distance, this will be reported as
    166 <code>'+/- ?'</code>.
    167 If the
    168 <em>host</em>
    169 is different from the
    170 <em>IP</em>,
    171 both will be displayed.
    172 Otherwise, only the 
    173 <em>IP</em>
    174 is displayed.
    175 Finally, the
    176 <em>stratum</em>
    177 of the host is reported
    178 and the leap indicator is decoded and displayed.
    179 </p>
    180 <p>This section was generated by <strong>AutoGen</strong>,
    181 using the <code>agtexi-cmd</code> template and the option descriptions for the <code>sntp</code> program.
    182 This software is released under the NTP license, &lt;http://ntp.org/license>;.
    183 </p>
    184 <table class="menu" border="0" cellspacing="0">
    185 <tr><td align="left" valign="top">&bull; <a href="#sntp-usage" accesskey="1">sntp usage</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">sntp help/usage (<samp>--help</samp>)
    186 </td></tr>
    187 <tr><td align="left" valign="top">&bull; <a href="#sntp-ipv4" accesskey="2">sntp ipv4</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">ipv4 option (-4)
    188 </td></tr>
    189 <tr><td align="left" valign="top">&bull; <a href="#sntp-ipv6" accesskey="3">sntp ipv6</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">ipv6 option (-6)
    190 </td></tr>
    191 <tr><td align="left" valign="top">&bull; <a href="#sntp-authentication" accesskey="4">sntp authentication</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">authentication option (-a)
    192 </td></tr>
    193 <tr><td align="left" valign="top">&bull; <a href="#sntp-broadcast" accesskey="5">sntp broadcast</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">broadcast option (-b)
    194 </td></tr>
    195 <tr><td align="left" valign="top">&bull; <a href="#sntp-concurrent" accesskey="6">sntp concurrent</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">concurrent option (-c)
    196 </td></tr>
    197 <tr><td align="left" valign="top">&bull; <a href="#sntp-gap" accesskey="7">sntp gap</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">gap option (-g)
    198 </td></tr>
    199 <tr><td align="left" valign="top">&bull; <a href="#sntp-kod" accesskey="8">sntp kod</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">kod option (-K)
    200 </td></tr>
    201 <tr><td align="left" valign="top">&bull; <a href="#sntp-keyfile" accesskey="9">sntp keyfile</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">keyfile option (-k)
    202 </td></tr>
    203 <tr><td align="left" valign="top">&bull; <a href="#sntp-logfile">sntp logfile</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">logfile option (-l)
    204 </td></tr>
    205 <tr><td align="left" valign="top">&bull; <a href="#sntp-steplimit">sntp steplimit</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">steplimit option (-M)
    206 </td></tr>
    207 <tr><td align="left" valign="top">&bull; <a href="#sntp-ntpversion">sntp ntpversion</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">ntpversion option (-o)
    208 </td></tr>
    209 <tr><td align="left" valign="top">&bull; <a href="#sntp-usereservedport">sntp usereservedport</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">usereservedport option (-r)
    210 </td></tr>
    211 <tr><td align="left" valign="top">&bull; <a href="#sntp-timeout">sntp timeout</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">timeout option (-t)
    212 </td></tr>
    213 <tr><td align="left" valign="top">&bull; <a href="#sntp-wait">sntp wait</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">wait option
    214 </td></tr>
    215 <tr><td align="left" valign="top">&bull; <a href="#sntp-config">sntp config</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">presetting/configuring sntp
    216 </td></tr>
    217 <tr><td align="left" valign="top">&bull; <a href="#sntp-exit-status">sntp exit status</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">exit status
    218 </td></tr>
    219 <tr><td align="left" valign="top">&bull; <a href="#sntp-Usage">sntp Usage</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Usage
    220 </td></tr>
    221 <tr><td align="left" valign="top">&bull; <a href="#sntp-Authors">sntp Authors</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Authors
    222 </td></tr>
    223 </table>
    224 
    225 <hr>
    226 <a name="sntp-usage"></a>
    227 <div class="header">
    228 <p>
    229 Next: <a href="#sntp-ipv4" accesskey="n" rel="next">sntp ipv4</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    230 </div>
    231 <a name="sntp-help_002fusage-_0028_002d_002dhelp_0029"></a>
    232 <h4 class="subsection">1.1.1 sntp help/usage (<samp>--help</samp>)</h4>
    233 <a name="index-sntp-help"></a>
    234 
    235 <p>This is the automatically generated usage text for sntp.
    236 </p>
    237 <p>The text printed is the same whether selected with the <code>help</code> option
    238 (<samp>--help</samp>) or the <code>more-help</code> option (<samp>--more-help</samp>).  <code>more-help</code> will print
    239 the usage text by passing it through a pager program.
    240 <code>more-help</code> is disabled on platforms without a working
    241 <code>fork(2)</code> function.  The <code>PAGER</code> environment variable is
    242 used to select the program, defaulting to <samp>more</samp>.  Both will exit
    243 with a status code of 0.
    244 </p>
    245 <div class="example">
    246 <pre class="example">sntp - standard Simple Network Time Protocol client program - Ver. 4.2.8p14
    247 Usage:  sntp [ -&lt;flag&gt; [&lt;val&gt;] | --&lt;name&gt;[{=| }&lt;val&gt;] ]... \
    248                 [ hostname-or-IP ...]
    249   Flg Arg Option-Name    Description
    250    -4 no  ipv4           Force IPv4 DNS name resolution
    251                                 - prohibits the option 'ipv6'
    252    -6 no  ipv6           Force IPv6 DNS name resolution
    253                                 - prohibits the option 'ipv4'
    254    -a Num authentication Enable authentication with the key auth-keynumber
    255    -b Str broadcast      Listen to the address specified for broadcast time sync
    256                                 - may appear multiple times
    257    -c Str concurrent     Concurrently query all IPs returned for host-name
    258                                 - may appear multiple times
    259    -d no  debug-level    Increase debug verbosity level
    260                                 - may appear multiple times
    261    -D Num set-debug-level Set the debug verbosity level
    262                                 - may appear multiple times
    263    -g Num gap            The gap (in milliseconds) between time requests
    264    -K Fil kod            KoD history filename
    265    -k Fil keyfile        Look in this file for the key specified with -a
    266    -l Fil logfile        Log to specified logfile
    267    -M Num steplimit      Adjustments less than steplimit msec will be slewed
    268                                 - it must be in the range:
    269                                   greater than or equal to 0
    270    -o Num ntpversion     Send int as our NTP protocol version
    271                                 - it must be in the range:
    272                                   0 to 7
    273    -r no  usereservedport Use the NTP Reserved Port (port 123)
    274    -S no  step           OK to 'step' the time with settimeofday(2)
    275    -s no  slew           OK to 'slew' the time with adjtime(2)
    276    -t Num timeout        The number of seconds to wait for responses
    277       no  wait           Wait for pending replies (if not setting the time)
    278                                 - disabled as '--no-wait'
    279                                 - enabled by default
    280       opt version        output version information and exit
    281    -? no  help           display extended usage information and exit
    282    -! no  more-help      extended usage information passed thru pager
    283    -&gt; opt save-opts      save the option state to a config file
    284    -&lt; Str load-opts      load options from a config file
    285                                 - disabled as '--no-load-opts'
    286                                 - may appear multiple times
    287 
    288 Options are specified by doubled hyphens and their name or by a single
    289 hyphen and the flag character.
    290 
    291 
    292 The following option preset mechanisms are supported:
    293  - reading file $HOME/.ntprc
    294  - reading file ./.ntprc
    295  - examining environment variables named SNTP_*
    296 
    297 Please send bug reports to:  &lt;http://bugs.ntp.org, bugs (a] ntp.org&gt;
    298 </pre></div>
    299 
    300 <hr>
    301 <a name="sntp-ipv4"></a>
    302 <div class="header">
    303 <p>
    304 Next: <a href="#sntp-ipv6" accesskey="n" rel="next">sntp ipv6</a>, Previous: <a href="#sntp-usage" accesskey="p" rel="prev">sntp usage</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    305 </div>
    306 <a name="ipv4-option-_0028_002d4_0029"></a>
    307 <h4 class="subsection">1.1.2 ipv4 option (-4)</h4>
    308 <a name="index-sntp_002dipv4"></a>
    309 
    310 <p>This is the &ldquo;force ipv4 dns name resolution&rdquo; option.
    311 </p>
    312 <p>This option has some usage constraints.  It:
    313 </p><ul>
    314 <li> must not appear in combination with any of the following options:
    315 ipv6.
    316 </li></ul>
    317 
    318 <p>Force DNS resolution of the following host names on the command line
    319 to the IPv4 namespace.
    320 </p><hr>
    321 <a name="sntp-ipv6"></a>
    322 <div class="header">
    323 <p>
    324 Next: <a href="#sntp-authentication" accesskey="n" rel="next">sntp authentication</a>, Previous: <a href="#sntp-ipv4" accesskey="p" rel="prev">sntp ipv4</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    325 </div>
    326 <a name="ipv6-option-_0028_002d6_0029"></a>
    327 <h4 class="subsection">1.1.3 ipv6 option (-6)</h4>
    328 <a name="index-sntp_002dipv6"></a>
    329 
    330 <p>This is the &ldquo;force ipv6 dns name resolution&rdquo; option.
    331 </p>
    332 <p>This option has some usage constraints.  It:
    333 </p><ul>
    334 <li> must not appear in combination with any of the following options:
    335 ipv4.
    336 </li></ul>
    337 
    338 <p>Force DNS resolution of the following host names on the command line
    339 to the IPv6 namespace.
    340 </p><hr>
    341 <a name="sntp-authentication"></a>
    342 <div class="header">
    343 <p>
    344 Next: <a href="#sntp-broadcast" accesskey="n" rel="next">sntp broadcast</a>, Previous: <a href="#sntp-ipv6" accesskey="p" rel="prev">sntp ipv6</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    345 </div>
    346 <a name="authentication-option-_0028_002da_0029"></a>
    347 <h4 class="subsection">1.1.4 authentication option (-a)</h4>
    348 <a name="index-sntp_002dauthentication"></a>
    349 
    350 <p>This is the &ldquo;enable authentication with the key <var>auth-keynumber</var>&rdquo; option.
    351 This option takes a number argument <samp>auth-keynumber</samp>.
    352 Enable authentication using the key specified in this option&rsquo;s
    353 argument.  The argument of this option is the <samp>keyid</samp>, a
    354 number specified in the <samp>keyfile</samp> as this key&rsquo;s identifier.
    355 See the <samp>keyfile</samp> option (<samp>-k</samp>) for more details.
    356 </p><hr>
    357 <a name="sntp-broadcast"></a>
    358 <div class="header">
    359 <p>
    360 Next: <a href="#sntp-concurrent" accesskey="n" rel="next">sntp concurrent</a>, Previous: <a href="#sntp-authentication" accesskey="p" rel="prev">sntp authentication</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    361 </div>
    362 <a name="broadcast-option-_0028_002db_0029"></a>
    363 <h4 class="subsection">1.1.5 broadcast option (-b)</h4>
    364 <a name="index-sntp_002dbroadcast"></a>
    365 
    366 <p>This is the &ldquo;listen to the address specified for broadcast time sync&rdquo; option.
    367 This option takes a string argument <samp>broadcast-address</samp>.
    368 </p>
    369 <p>This option has some usage constraints.  It:
    370 </p><ul>
    371 <li> may appear an unlimited number of times.
    372 </li></ul>
    373 
    374 <p>If specified <code>sntp</code> will listen to the specified address
    375 for NTP broadcasts.  The default maximum wait time
    376 can (and probably should) be modified with <samp>-t</samp>.
    377 </p><hr>
    378 <a name="sntp-concurrent"></a>
    379 <div class="header">
    380 <p>
    381 Next: <a href="#sntp-gap" accesskey="n" rel="next">sntp gap</a>, Previous: <a href="#sntp-broadcast" accesskey="p" rel="prev">sntp broadcast</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    382 </div>
    383 <a name="concurrent-option-_0028_002dc_0029"></a>
    384 <h4 class="subsection">1.1.6 concurrent option (-c)</h4>
    385 <a name="index-sntp_002dconcurrent"></a>
    386 
    387 <p>This is the &ldquo;concurrently query all ips returned for host-name&rdquo; option.
    388 This option takes a string argument <samp>host-name</samp>.
    389 </p>
    390 <p>This option has some usage constraints.  It:
    391 </p><ul>
    392 <li> may appear an unlimited number of times.
    393 </li></ul>
    394 
    395 <p>Requests from an NTP &quot;client&quot; to a &quot;server&quot; should never be sent
    396 more rapidly than one every 2 seconds.  By default, any IPs returned
    397 as part of a DNS lookup are assumed to be for a single instance of
    398 <code>ntpd</code>, and therefore <code>sntp</code> will send queries to these IPs
    399 one after another, with a 2-second gap in between each query.
    400 </p>
    401 <p>The <samp>-c</samp> or <samp>--concurrent</samp> flag says that any IPs
    402 returned for the DNS lookup of the supplied host-name are on
    403 different machines, so we can send concurrent queries.
    404 </p><hr>
    405 <a name="sntp-gap"></a>
    406 <div class="header">
    407 <p>
    408 Next: <a href="#sntp-kod" accesskey="n" rel="next">sntp kod</a>, Previous: <a href="#sntp-concurrent" accesskey="p" rel="prev">sntp concurrent</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    409 </div>
    410 <a name="gap-option-_0028_002dg_0029"></a>
    411 <h4 class="subsection">1.1.7 gap option (-g)</h4>
    412 <a name="index-sntp_002dgap"></a>
    413 
    414 <p>This is the &ldquo;the gap (in milliseconds) between time requests&rdquo; option.
    415 This option takes a number argument <samp>milliseconds</samp>.
    416 Since we&rsquo;re only going to use the first valid response we get and
    417 there is benefit to specifying a good number of servers to query,
    418 separate the queries we send out by the specified number of
    419 milliseconds.
    420 </p><hr>
    421 <a name="sntp-kod"></a>
    422 <div class="header">
    423 <p>
    424 Next: <a href="#sntp-keyfile" accesskey="n" rel="next">sntp keyfile</a>, Previous: <a href="#sntp-gap" accesskey="p" rel="prev">sntp gap</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    425 </div>
    426 <a name="kod-option-_0028_002dK_0029"></a>
    427 <h4 class="subsection">1.1.8 kod option (-K)</h4>
    428 <a name="index-sntp_002dkod"></a>
    429 
    430 <p>This is the &ldquo;kod history filename&rdquo; option.
    431 This option takes a file argument <samp>file-name</samp>.
    432 Specifies the filename to be used for the persistent history of KoD
    433 responses received from servers.  If the file does not exist, a
    434 warning message will be displayed.  The file will not be created.
    435 </p><hr>
    436 <a name="sntp-keyfile"></a>
    437 <div class="header">
    438 <p>
    439 Next: <a href="#sntp-logfile" accesskey="n" rel="next">sntp logfile</a>, Previous: <a href="#sntp-kod" accesskey="p" rel="prev">sntp kod</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    440 </div>
    441 <a name="keyfile-option-_0028_002dk_0029"></a>
    442 <h4 class="subsection">1.1.9 keyfile option (-k)</h4>
    443 <a name="index-sntp_002dkeyfile"></a>
    444 
    445 <p>This is the &ldquo;look in this file for the key specified with <samp>-a</samp>&rdquo; option.
    446 This option takes a file argument <samp>file-name</samp>.
    447 This option specifies the keyfile.
    448 <code>sntp</code> will search for the key specified with <samp>-a</samp>
    449 <samp>keyno</samp> in this file.  See <code>ntp.keys(5)</code> for more
    450 information.
    451 </p><hr>
    452 <a name="sntp-logfile"></a>
    453 <div class="header">
    454 <p>
    455 Next: <a href="#sntp-steplimit" accesskey="n" rel="next">sntp steplimit</a>, Previous: <a href="#sntp-keyfile" accesskey="p" rel="prev">sntp keyfile</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    456 </div>
    457 <a name="logfile-option-_0028_002dl_0029"></a>
    458 <h4 class="subsection">1.1.10 logfile option (-l)</h4>
    459 <a name="index-sntp_002dlogfile"></a>
    460 
    461 <p>This is the &ldquo;log to specified logfile&rdquo; option.
    462 This option takes a file argument <samp>file-name</samp>.
    463 This option causes the client to write log messages to the specified
    464 <samp>logfile</samp>.
    465 </p><hr>
    466 <a name="sntp-steplimit"></a>
    467 <div class="header">
    468 <p>
    469 Next: <a href="#sntp-ntpversion" accesskey="n" rel="next">sntp ntpversion</a>, Previous: <a href="#sntp-logfile" accesskey="p" rel="prev">sntp logfile</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    470 </div>
    471 <a name="steplimit-option-_0028_002dM_0029"></a>
    472 <h4 class="subsection">1.1.11 steplimit option (-M)</h4>
    473 <a name="index-sntp_002dsteplimit"></a>
    474 
    475 <p>This is the &ldquo;adjustments less than <var>steplimit</var> msec will be slewed&rdquo; option.
    476 This option takes a number argument.
    477 If the time adjustment is less than <samp>steplimit</samp> milliseconds,
    478 slew the amount using <code>adjtime(2)</code>.  Otherwise, step the
    479 correction using <code>settimeofday(2)</code>.  The default value is 0,
    480 which means all adjustments will be stepped.  This is a feature, as
    481 different situations demand different values.
    482 </p><hr>
    483 <a name="sntp-ntpversion"></a>
    484 <div class="header">
    485 <p>
    486 Next: <a href="#sntp-usereservedport" accesskey="n" rel="next">sntp usereservedport</a>, Previous: <a href="#sntp-steplimit" accesskey="p" rel="prev">sntp steplimit</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    487 </div>
    488 <a name="ntpversion-option-_0028_002do_0029"></a>
    489 <h4 class="subsection">1.1.12 ntpversion option (-o)</h4>
    490 <a name="index-sntp_002dntpversion"></a>
    491 
    492 <p>This is the &ldquo;send <var>int</var> as our ntp protocol version&rdquo; option.
    493 This option takes a number argument.
    494 When sending requests to a remote server, tell them we are running
    495 NTP protocol version <samp>ntpversion</samp> .
    496 </p><hr>
    497 <a name="sntp-usereservedport"></a>
    498 <div class="header">
    499 <p>
    500 Next: <a href="#sntp-timeout" accesskey="n" rel="next">sntp timeout</a>, Previous: <a href="#sntp-ntpversion" accesskey="p" rel="prev">sntp ntpversion</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    501 </div>
    502 <a name="usereservedport-option-_0028_002dr_0029"></a>
    503 <h4 class="subsection">1.1.13 usereservedport option (-r)</h4>
    504 <a name="index-sntp_002dusereservedport"></a>
    505 
    506 <p>This is the &ldquo;use the ntp reserved port (port 123)&rdquo; option.
    507 Use port 123, which is reserved for NTP, for our network
    508 communications.
    509 </p><hr>
    510 <a name="sntp-timeout"></a>
    511 <div class="header">
    512 <p>
    513 Next: <a href="#sntp-wait" accesskey="n" rel="next">sntp wait</a>, Previous: <a href="#sntp-usereservedport" accesskey="p" rel="prev">sntp usereservedport</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    514 </div>
    515 <a name="timeout-option-_0028_002dt_0029"></a>
    516 <h4 class="subsection">1.1.14 timeout option (-t)</h4>
    517 <a name="index-sntp_002dtimeout"></a>
    518 
    519 <p>This is the &ldquo;the number of seconds to wait for responses&rdquo; option.
    520 This option takes a number argument <samp>seconds</samp>.
    521 When waiting for a reply, <code>sntp</code> will wait the number
    522 of seconds specified before giving up.  The default should be
    523 more than enough for a unicast response.  If <code>sntp</code> is
    524 only waiting for a broadcast response a longer timeout is
    525 likely needed.
    526 </p><hr>
    527 <a name="sntp-wait"></a>
    528 <div class="header">
    529 <p>
    530 Next: <a href="#sntp-config" accesskey="n" rel="next">sntp config</a>, Previous: <a href="#sntp-timeout" accesskey="p" rel="prev">sntp timeout</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    531 </div>
    532 <a name="wait-option"></a>
    533 <h4 class="subsection">1.1.15 wait option</h4>
    534 <a name="index-sntp_002dwait"></a>
    535 
    536 <p>This is the &ldquo;wait for pending replies (if not setting the time)&rdquo; option.
    537 </p>
    538 <p>This option has some usage constraints.  It:
    539 </p><ul>
    540 <li> can be disabled with &ndash;no-wait.
    541 </li><li> It is enabled by default.
    542 </li></ul>
    543 
    544 <p>If we are not setting the time, wait for all pending responses.
    545 </p>
    546 
    547 <hr>
    548 <a name="sntp-config"></a>
    549 <div class="header">
    550 <p>
    551 Next: <a href="#sntp-exit-status" accesskey="n" rel="next">sntp exit status</a>, Previous: <a href="#sntp-wait" accesskey="p" rel="prev">sntp wait</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    552 </div>
    553 <a name="presetting_002fconfiguring-sntp"></a>
    554 <h4 class="subsection">1.1.16 presetting/configuring sntp</h4>
    555 
    556 <p>Any option that is not marked as <i>not presettable</i> may be preset by
    557 loading values from configuration (&quot;rc&quot; or &quot;ini&quot;) files, and values from environment variables named <code>SNTP</code> and <code>SNTP_&lt;OPTION_NAME&gt;</code>.  <code>&lt;OPTION_NAME&gt;</code> must be one of
    558 the options listed above in upper case and segmented with underscores.
    559 The <code>SNTP</code> variable will be tokenized and parsed like
    560 the command line.  The remaining variables are tested for existence and their
    561 values are treated like option arguments.
    562 </p>
    563 
    564 <p><code>libopts</code> will search in 2 places for configuration files:
    565 </p><ul>
    566 <li> $HOME
    567 </li><li> $PWD
    568 </li></ul>
    569 <p>The environment variables <code>HOME</code>, and <code>PWD</code>
    570 are expanded and replaced when <samp>sntp</samp> runs.
    571 For any of these that are plain files, they are simply processed.
    572 For any that are directories, then a file named <samp>.ntprc</samp> is searched for
    573 within that directory and processed.
    574 </p>
    575 <p>Configuration files may be in a wide variety of formats.
    576 The basic format is an option name followed by a value (argument) on the
    577 same line.  Values may be separated from the option name with a colon,
    578 equal sign or simply white space.  Values may be continued across multiple
    579 lines by escaping the newline with a backslash.
    580 </p>
    581 <p>Multiple programs may also share the same initialization file.
    582 Common options are collected at the top, followed by program specific
    583 segments.  The segments are separated by lines like:
    584 </p><div class="example">
    585 <pre class="example">[SNTP]
    586 </pre></div>
    587 <p>or by
    588 </p><div class="example">
    589 <pre class="example">&lt;?program sntp&gt;
    590 </pre></div>
    591 <p>Do not mix these styles within one configuration file.
    592 </p>
    593 <p>Compound values and carefully constructed string values may also be
    594 specified using XML syntax:
    595 </p><div class="example">
    596 <pre class="example">&lt;option-name&gt;
    597    &lt;sub-opt&gt;...&amp;lt;...&amp;gt;...&lt;/sub-opt&gt;
    598 &lt;/option-name&gt;
    599 </pre></div>
    600 <p>yielding an <code>option-name.sub-opt</code> string value of
    601 </p><div class="example">
    602 <pre class="example">&quot;...&lt;...&gt;...&quot;
    603 </pre></div>
    604 <p><code>AutoOpts</code> does not track suboptions.  You simply note that it is a
    605 hierarchicly valued option.  <code>AutoOpts</code> does provide a means for searching
    606 the associated name/value pair list (see: optionFindValue).
    607 </p>
    608 <p>The command line options relating to configuration and/or usage help are:
    609 </p>
    610 <a name="version-_0028_002d_0029"></a>
    611 <h4 class="subsubheading">version (-)</h4>
    612 
    613 <p>Print the program version to standard out, optionally with licensing
    614 information, then exit 0.  The optional argument specifies how much licensing
    615 detail to provide.  The default is to print just the version.  The licensing infomation may be selected with an option argument.
    616 Only the first letter of the argument is examined:
    617 </p>
    618 <dl compact="compact">
    619 <dt>&lsquo;<samp>version</samp>&rsquo;</dt>
    620 <dd><p>Only print the version.  This is the default.
    621 </p></dd>
    622 <dt>&lsquo;<samp>copyright</samp>&rsquo;</dt>
    623 <dd><p>Name the copyright usage licensing terms.
    624 </p></dd>
    625 <dt>&lsquo;<samp>verbose</samp>&rsquo;</dt>
    626 <dd><p>Print the full copyright usage licensing terms.
    627 </p></dd>
    628 </dl>
    629 
    630 <hr>
    631 <a name="sntp-exit-status"></a>
    632 <div class="header">
    633 <p>
    634 Next: <a href="#sntp-Usage" accesskey="n" rel="next">sntp Usage</a>, Previous: <a href="#sntp-config" accesskey="p" rel="prev">sntp config</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    635 </div>
    636 <a name="sntp-exit-status-1"></a>
    637 <h4 class="subsection">1.1.17 sntp exit status</h4>
    638 
    639 <p>One of the following exit values will be returned:
    640 </p><dl compact="compact">
    641 <dt>&lsquo;<samp>0 (EXIT_SUCCESS)</samp>&rsquo;</dt>
    642 <dd><p>Successful program execution.
    643 </p></dd>
    644 <dt>&lsquo;<samp>1 (EXIT_FAILURE)</samp>&rsquo;</dt>
    645 <dd><p>The operation failed or the command syntax was not valid.
    646 </p></dd>
    647 <dt>&lsquo;<samp>66 (EX_NOINPUT)</samp>&rsquo;</dt>
    648 <dd><p>A specified configuration file could not be loaded.
    649 </p></dd>
    650 <dt>&lsquo;<samp>70 (EX_SOFTWARE)</samp>&rsquo;</dt>
    651 <dd><p>libopts had an internal operational error.  Please report
    652 it to autogen-users (a] lists.sourceforge.net.  Thank you.
    653 </p></dd>
    654 </dl>
    655 <hr>
    656 <a name="sntp-Usage"></a>
    657 <div class="header">
    658 <p>
    659 Next: <a href="#sntp-Authors" accesskey="n" rel="next">sntp Authors</a>, Previous: <a href="#sntp-exit-status" accesskey="p" rel="prev">sntp exit status</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    660 </div>
    661 <a name="sntp-Usage-1"></a>
    662 <h4 class="subsection">1.1.18 sntp Usage</h4>
    663 <hr>
    664 <a name="sntp-Authors"></a>
    665 <div class="header">
    666 <p>
    667 Previous: <a href="#sntp-Usage" accesskey="p" rel="prev">sntp Usage</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> &nbsp; </p>
    668 </div>
    669 <a name="sntp-Authors-1"></a>
    670 <h4 class="subsection">1.1.19 sntp Authors</h4>
    671 
    672 <hr>
    673 <a name="Usage"></a>
    674 <div class="header">
    675 <p>
    676 Previous: <a href="#sntp-Invocation" accesskey="p" rel="prev">sntp Invocation</a>, Up: <a href="#sntp-Description" accesskey="u" rel="up">sntp Description</a> &nbsp; </p>
    677 </div>
    678 <a name="Usage-1"></a>
    679 <h3 class="section">1.2 Usage</h3>
    680 
    681 <p>The simplest use of this program is as an unprivileged command to
    682 check the current time, offset, and error in the local clock.
    683 For example:
    684 </p>
    685 <div class="example">
    686 <pre class="example">sntp ntpserver.somewhere
    687 </pre></div>
    688 
    689 <p>With suitable privilege, it can be run as a command or in a
    690 <code>crom</code> job to reset the local clock from a reliable server, like
    691 the <code>ntpdate</code> and <code>rdate</code> commands.
    692 For example:
    693 </p>
    694 <div class="example">
    695 <pre class="example">sntp -a ntpserver.somewhere
    696 </pre></div>
    697 <hr>
    698 
    699 
    700 
    701 </body>
    702 </html>
    703