1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<!-- Created by GNU Texinfo 6.5, http://www.gnu.org/software/texinfo/ --> 4<head> 5<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 6<title>Sntp User’s Manual</title> 7 8<meta name="description" content="Sntp User’s Manual"> 9<meta name="keywords" content="Sntp User’s Manual"> 10<meta name="resource-type" content="document"> 11<meta name="distribution" content="global"> 12<meta name="Generator" content="makeinfo"> 13<link href="#Top" rel="start" title="Top"> 14<link href="dir.html#Top" rel="up" title="(dir)"> 15<style type="text/css"> 16<!-- 17a.summary-letter {text-decoration: none} 18blockquote.indentedblock {margin-right: 0em} 19blockquote.smallindentedblock {margin-right: 0em; font-size: smaller} 20blockquote.smallquotation {font-size: smaller} 21div.display {margin-left: 3.2em} 22div.example {margin-left: 3.2em} 23div.lisp {margin-left: 3.2em} 24div.smalldisplay {margin-left: 3.2em} 25div.smallexample {margin-left: 3.2em} 26div.smalllisp {margin-left: 3.2em} 27kbd {font-style: oblique} 28pre.display {font-family: inherit} 29pre.format {font-family: inherit} 30pre.menu-comment {font-family: serif} 31pre.menu-preformatted {font-family: serif} 32pre.smalldisplay {font-family: inherit; font-size: smaller} 33pre.smallexample {font-size: smaller} 34pre.smallformat {font-family: inherit; font-size: smaller} 35pre.smalllisp {font-size: smaller} 36span.nolinebreak {white-space: nowrap} 37span.roman {font-family: initial; font-weight: normal} 38span.sansserif {font-family: sans-serif; font-weight: normal} 39ul.no-bullet {list-style: none} 40--> 41</style> 42 43 44</head> 45 46<body lang="en"> 47<h1 class="settitle" align="center">Sntp User’s Manual</h1> 48 49 50 51 52 53<a name="Top"></a> 54<div class="header"> 55<p> 56Next: <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> </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’s <code>sntp</code> program, 62that can be used to query a Network Time Protocol (NTP) server and 63display the time offset of the system clock relative to the server 64clock. Run as root, it can correct the system clock to this offset as 65well. It can be run as an interactive command or from a cron job. 66</p> 67<p>This document applies to version 4.2.8p15 of <code>sntp</code>. 68</p> 69<p>The program implements the SNTP protocol as defined by RFC 5905, the NTPv4 70IETF 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">• <a href="#sntp-Description" accesskey="1">sntp Description</a>:</td><td> </td><td align="left" valign="top">Description 84</td></tr> 85<tr><td align="left" valign="top">• <a href="#sntp-Invocation" accesskey="2">sntp Invocation</a>:</td><td> </td><td align="left" valign="top">Invoking sntp 86</td></tr> 87<tr><td align="left" valign="top">• <a href="#Usage" accesskey="3">Usage</a>:</td><td> </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> 95Next: <a href="#sntp-Invocation" accesskey="n" rel="next">sntp Invocation</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> </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 101standard 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 108YYYY-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), 110and 111the +4.567 +/- 0.089 secs indicates the time offset and 112error 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">• <a href="#sntp-Invocation" accesskey="1">sntp Invocation</a>:</td><td> </td><td align="left" valign="top"> 116</td></tr> 117<tr><td align="left" valign="top">• <a href="#Usage" accesskey="2">Usage</a>:</td><td> </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> 125Next: <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> </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> 135can be used as an SNTP client to query a NTP or SNTP server and either display 136the time or set the local system’s time (given suitable privilege). It can be 137run as an interactive command or from a 138<code>cron</code> 139job. 140</p> 141<p>NTP (the Network Time Protocol) and SNTP (the Simple Network Time Protocol) 142are 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 146UTC) 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> 152means that to get to UTC from the reported local time one must 153add 8 hours and 0 minutes, 154the 155<code>'+4.567'</code> 156indicates 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). 158Note that the number of decimals printed for this value will change 159based on the reported precision of the server. 160<code>'+/- 0.089'</code> 161is the reported 162<em>synchronization</em> <em>distance</em> 163(in seconds), which represents the maximum error due to all causes. 164If the server does not report valid data needed to calculate the 165synchronization distance, this will be reported as 166<code>'+/- ?'</code>. 167If the 168<em>host</em> 169is different from the 170<em>IP</em>, 171both will be displayed. 172Otherwise, only the 173<em>IP</em> 174is displayed. 175Finally, the 176<em>stratum</em> 177of the host is reported 178and the leap indicator is decoded and displayed. 179</p> 180<p>This section was generated by <strong>AutoGen</strong>, 181using the <code>agtexi-cmd</code> template and the option descriptions for the <code>sntp</code> program. 182This software is released under the NTP license, <http://ntp.org/license>;. 183</p> 184<table class="menu" border="0" cellspacing="0"> 185<tr><td align="left" valign="top">• <a href="#sntp-usage" accesskey="1">sntp usage</a>:</td><td> </td><td align="left" valign="top">sntp help/usage (<samp>--help</samp>) 186</td></tr> 187<tr><td align="left" valign="top">• <a href="#sntp-ipv4" accesskey="2">sntp ipv4</a>:</td><td> </td><td align="left" valign="top">ipv4 option (-4) 188</td></tr> 189<tr><td align="left" valign="top">• <a href="#sntp-ipv6" accesskey="3">sntp ipv6</a>:</td><td> </td><td align="left" valign="top">ipv6 option (-6) 190</td></tr> 191<tr><td align="left" valign="top">• <a href="#sntp-authentication" accesskey="4">sntp authentication</a>:</td><td> </td><td align="left" valign="top">authentication option (-a) 192</td></tr> 193<tr><td align="left" valign="top">• <a href="#sntp-broadcast" accesskey="5">sntp broadcast</a>:</td><td> </td><td align="left" valign="top">broadcast option (-b) 194</td></tr> 195<tr><td align="left" valign="top">• <a href="#sntp-concurrent" accesskey="6">sntp concurrent</a>:</td><td> </td><td align="left" valign="top">concurrent option (-c) 196</td></tr> 197<tr><td align="left" valign="top">• <a href="#sntp-gap" accesskey="7">sntp gap</a>:</td><td> </td><td align="left" valign="top">gap option (-g) 198</td></tr> 199<tr><td align="left" valign="top">• <a href="#sntp-kod" accesskey="8">sntp kod</a>:</td><td> </td><td align="left" valign="top">kod option (-K) 200</td></tr> 201<tr><td align="left" valign="top">• <a href="#sntp-keyfile" accesskey="9">sntp keyfile</a>:</td><td> </td><td align="left" valign="top">keyfile option (-k) 202</td></tr> 203<tr><td align="left" valign="top">• <a href="#sntp-logfile">sntp logfile</a>:</td><td> </td><td align="left" valign="top">logfile option (-l) 204</td></tr> 205<tr><td align="left" valign="top">• <a href="#sntp-steplimit">sntp steplimit</a>:</td><td> </td><td align="left" valign="top">steplimit option (-M) 206</td></tr> 207<tr><td align="left" valign="top">• <a href="#sntp-ntpversion">sntp ntpversion</a>:</td><td> </td><td align="left" valign="top">ntpversion option (-o) 208</td></tr> 209<tr><td align="left" valign="top">• <a href="#sntp-usereservedport">sntp usereservedport</a>:</td><td> </td><td align="left" valign="top">usereservedport option (-r) 210</td></tr> 211<tr><td align="left" valign="top">• <a href="#sntp-timeout">sntp timeout</a>:</td><td> </td><td align="left" valign="top">timeout option (-t) 212</td></tr> 213<tr><td align="left" valign="top">• <a href="#sntp-wait">sntp wait</a>:</td><td> </td><td align="left" valign="top">wait option 214</td></tr> 215<tr><td align="left" valign="top">• <a href="#sntp-config">sntp config</a>:</td><td> </td><td align="left" valign="top">presetting/configuring sntp 216</td></tr> 217<tr><td align="left" valign="top">• <a href="#sntp-exit-status">sntp exit status</a>:</td><td> </td><td align="left" valign="top">exit status 218</td></tr> 219<tr><td align="left" valign="top">• <a href="#sntp-Usage">sntp Usage</a>:</td><td> </td><td align="left" valign="top">Usage 220</td></tr> 221<tr><td align="left" valign="top">• <a href="#sntp-Authors">sntp Authors</a>:</td><td> </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> 229Next: <a href="#sntp-ipv4" accesskey="n" rel="next">sntp ipv4</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> </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 239the 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 242used to select the program, defaulting to <samp>more</samp>. Both will exit 243with a status code of 0. 244</p> 245<div class="example"> 246<pre class="example">sntp - standard Simple Network Time Protocol client program - Ver. 4.2.8p15 247Usage: sntp [ -<flag> [<val>] | --<name>[{=| }<val>] ]... \ 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 -> opt save-opts save the option state to a config file 284 -< Str load-opts load options from a config file 285 - disabled as '--no-load-opts' 286 - may appear multiple times 287 288Options are specified by doubled hyphens and their name or by a single 289hyphen and the flag character. 290 291 292The following option preset mechanisms are supported: 293 - reading file $HOME/.ntprc 294 - reading file ./.ntprc 295 - examining environment variables named SNTP_* 296 297Please send bug reports to: <http://bugs.ntp.org, bugs@ntp.org> 298</pre></div> 299 300<hr> 301<a name="sntp-ipv4"></a> 302<div class="header"> 303<p> 304Next: <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> </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 “force ipv4 dns name resolution” 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: 315ipv6. 316</li></ul> 317 318<p>Force DNS resolution of the following host names on the command line 319to the IPv4 namespace. 320</p><hr> 321<a name="sntp-ipv6"></a> 322<div class="header"> 323<p> 324Next: <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> </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 “force ipv6 dns name resolution” 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: 335ipv4. 336</li></ul> 337 338<p>Force DNS resolution of the following host names on the command line 339to the IPv6 namespace. 340</p><hr> 341<a name="sntp-authentication"></a> 342<div class="header"> 343<p> 344Next: <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> </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 “enable authentication with the key <var>auth-keynumber</var>” option. 351This option takes a number argument <samp>auth-keynumber</samp>. 352Enable authentication using the key specified in this option’s 353argument. The argument of this option is the <samp>keyid</samp>, a 354number specified in the <samp>keyfile</samp> as this key’s identifier. 355See 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> 360Next: <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> </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 “listen to the address specified for broadcast time sync” option. 367This 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 375for NTP broadcasts. The default maximum wait time 376can (and probably should) be modified with <samp>-t</samp>. 377</p><hr> 378<a name="sntp-concurrent"></a> 379<div class="header"> 380<p> 381Next: <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> </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 “concurrently query all ips returned for host-name” option. 388This 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 "client" to a "server" should never be sent 396more rapidly than one every 2 seconds. By default, any IPs returned 397as 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 399one 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 402returned for the DNS lookup of the supplied host-name are on 403different machines, so we can send concurrent queries. 404</p><hr> 405<a name="sntp-gap"></a> 406<div class="header"> 407<p> 408Next: <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> </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 “the gap (in milliseconds) between time requests” option. 415This option takes a number argument <samp>milliseconds</samp>. 416Since we’re only going to use the first valid response we get and 417there is benefit to specifying a good number of servers to query, 418separate the queries we send out by the specified number of 419milliseconds. 420</p><hr> 421<a name="sntp-kod"></a> 422<div class="header"> 423<p> 424Next: <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> </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 “kod history filename” option. 431This option takes a file argument <samp>file-name</samp>. 432Specifies the filename to be used for the persistent history of KoD 433responses received from servers. If the file does not exist, a 434warning 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> 439Next: <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> </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 “look in this file for the key specified with <samp>-a</samp>” option. 446This option takes a file argument <samp>file-name</samp>. 447This 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 450information. 451</p><hr> 452<a name="sntp-logfile"></a> 453<div class="header"> 454<p> 455Next: <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> </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 “log to specified logfile” option. 462This option takes a file argument <samp>file-name</samp>. 463This 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> 469Next: <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> </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 “adjustments less than <var>steplimit</var> msec will be slewed” option. 476This option takes a number argument. 477If the time adjustment is less than <samp>steplimit</samp> milliseconds, 478slew the amount using <code>adjtime(2)</code>. Otherwise, step the 479correction using <code>settimeofday(2)</code>. The default value is 0, 480which means all adjustments will be stepped. This is a feature, as 481different situations demand different values. 482</p><hr> 483<a name="sntp-ntpversion"></a> 484<div class="header"> 485<p> 486Next: <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> </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 “send <var>int</var> as our ntp protocol version” option. 493This option takes a number argument. 494When sending requests to a remote server, tell them we are running 495NTP protocol version <samp>ntpversion</samp> . 496</p><hr> 497<a name="sntp-usereservedport"></a> 498<div class="header"> 499<p> 500Next: <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> </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 “use the ntp reserved port (port 123)” option. 507Use port 123, which is reserved for NTP, for our network 508communications. 509</p><hr> 510<a name="sntp-timeout"></a> 511<div class="header"> 512<p> 513Next: <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> </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 “the number of seconds to wait for responses” option. 520This option takes a number argument <samp>seconds</samp>. 521When waiting for a reply, <code>sntp</code> will wait the number 522of seconds specified before giving up. The default should be 523more than enough for a unicast response. If <code>sntp</code> is 524only waiting for a broadcast response a longer timeout is 525likely needed. 526</p><hr> 527<a name="sntp-wait"></a> 528<div class="header"> 529<p> 530Next: <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> </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 “wait for pending replies (if not setting the time)” option. 537</p> 538<p>This option has some usage constraints. It: 539</p><ul> 540<li> can be disabled with –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> 551Next: <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> </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 557loading 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 558the options listed above in upper case and segmented with underscores. 559The <code>SNTP</code> variable will be tokenized and parsed like 560the command line. The remaining variables are tested for existence and their 561values 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> 570are expanded and replaced when <samp>sntp</samp> runs. 571For any of these that are plain files, they are simply processed. 572For any that are directories, then a file named <samp>.ntprc</samp> is searched for 573within that directory and processed. 574</p> 575<p>Configuration files may be in a wide variety of formats. 576The basic format is an option name followed by a value (argument) on the 577same line. Values may be separated from the option name with a colon, 578equal sign or simply white space. Values may be continued across multiple 579lines by escaping the newline with a backslash. 580</p> 581<p>Multiple programs may also share the same initialization file. 582Common options are collected at the top, followed by program specific 583segments. 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"><?program sntp> 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 594specified using XML syntax: 595</p><div class="example"> 596<pre class="example"><option-name> 597 <sub-opt>...&lt;...&gt;...</sub-opt> 598</option-name> 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">"...<...>..." 603</pre></div> 604<p><code>AutoOpts</code> does not track suboptions. You simply note that it is a 605hierarchicly valued option. <code>AutoOpts</code> does provide a means for searching 606the 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 614information, then exit 0. The optional argument specifies how much licensing 615detail to provide. The default is to print just the version. The licensing infomation may be selected with an option argument. 616Only the first letter of the argument is examined: 617</p> 618<dl compact="compact"> 619<dt>‘<samp>version</samp>’</dt> 620<dd><p>Only print the version. This is the default. 621</p></dd> 622<dt>‘<samp>copyright</samp>’</dt> 623<dd><p>Name the copyright usage licensing terms. 624</p></dd> 625<dt>‘<samp>verbose</samp>’</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> 634Next: <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> </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>‘<samp>0 (EXIT_SUCCESS)</samp>’</dt> 642<dd><p>Successful program execution. 643</p></dd> 644<dt>‘<samp>1 (EXIT_FAILURE)</samp>’</dt> 645<dd><p>The operation failed or the command syntax was not valid. 646</p></dd> 647<dt>‘<samp>66 (EX_NOINPUT)</samp>’</dt> 648<dd><p>A specified configuration file could not be loaded. 649</p></dd> 650<dt>‘<samp>70 (EX_SOFTWARE)</samp>’</dt> 651<dd><p>libopts had an internal operational error. Please report 652it to autogen-users@lists.sourceforge.net. Thank you. 653</p></dd> 654</dl> 655<hr> 656<a name="sntp-Usage"></a> 657<div class="header"> 658<p> 659Next: <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> </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> 667Previous: <a href="#sntp-Usage" accesskey="p" rel="prev">sntp Usage</a>, Up: <a href="#sntp-Invocation" accesskey="u" rel="up">sntp Invocation</a> </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> 676Previous: <a href="#sntp-Invocation" accesskey="p" rel="prev">sntp Invocation</a>, Up: <a href="#sntp-Description" accesskey="u" rel="up">sntp Description</a> </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 682check the current time, offset, and error in the local clock. 683For 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 691the <code>ntpdate</code> and <code>rdate</code> commands. 692For 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