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Diffstat (limited to 'doc/flags.html')
| -rw-r--r-- | doc/flags.html | 58 |
1 files changed, 10 insertions, 48 deletions
diff --git a/doc/flags.html b/doc/flags.html index a7bdab8..f519685 100644 --- a/doc/flags.html +++ b/doc/flags.html @@ -71,7 +71,7 @@ tested, so it's usually safe, and faster, to stick to the default. <a name="clockistai"><h3> --enable-tai-clock </h3></a> <p> - To understand what this flag is about - and the next three flags too - you + To understand what this flag is about - and the next two flags too - you should start by reading <a href="http://www.madore.org/~david/computers/unix-leap-seconds.html">this page about Unix time</a>, @@ -105,10 +105,13 @@ and makes event loop handling (with functions such as <li> ↑ skalibs uses TAI internally; setting your system clock to TAI-10 saves a lot of conversions and makes time computations with skalibs more efficient. </li> - <li> → In order to display GMT or local time properly, you have to -use the <tt>right/</tt> timezones from Arthur David Olson's timezone -library. If your libc does not support them, see the -<a href="#tzisright">next flag</a>. </li> + <li> → skalibs-aware software will display GMT or local time properly in +every case, but you have to +use the <tt>right/</tt> timezones, from Arthur David Olson's timezone +library, to prevent your other software from being confused by a TAI-10 system clock. +If you do not use <tt>right/</tt> timezones, utilities such as <tt>date</tt> +will not compute the proper time - they will have an offset of 24 seconds +or so. </li> <li> ↓ This setup is arguably not SUSv4 conformant (a strict interpretation of Single Unix requires the system clock to be set to UTC). </li> <li> ↓ This setup is <em>not</em> compatible with @@ -126,7 +129,8 @@ POSIX setup: <li> ↑ This is strictly SUSv4-compliant. Most Unix machines all over the world are set up like this. </li> <li> ↑ This is compatible with ntpd. </li> - <li> → You should not use Olson's time library in that case. </li> + <li> → You should use <tt>posix/</tt> time zones in that case, +not <tt>right/</tt> time zones. </li> <li> ↓ skalibs time computations will take a bit more processing power. </li> <li> ↓ Most importantly, you forsake all linearity - and even monotonicity - on your system clock, which can now only be used as a wall clock, @@ -154,48 +158,6 @@ POSIX freak, or your Unix distribution is running ntpd for you, or other software is assuming you're on UTC. This is the default. </p> - -<a name="tzisright"><h3> --enable-right-tz </h3> - -<p> - This option instructs skalibs that you're using Olson's time -library, i.e. "right/" timezones. -</p> - -<p> - Normally, if you set <a href="#clockistai">--enable-tai-clock</a>, you -<em>should</em> also set up your timezone to a "right/" one, and -set <tt>flag-tzisright</tt>. And if you don't use -<a href="#clockistai">--enable-tai-clock</a>, you should also use a POSIX -timezone, and NOT use <tt>--enable-right-tz</tt>. Those two options -should always be used together. -</p> - -<p> - <em>But</em> some C libraries do not support the Olson time library's -timezone format, and just do not provide the "right/" timezones! For -instance, <a href="http://musl-libc.org/">musl</a>, -an alternative libc for Linux, only supports POSIX timezones. And you -might want to use such a libc, and <em>still</em> set up your clock to -TAI-10, for instance in embedded environments where accurate timekeeping -is important. In such cases, you'll set up a POSIX timezone, and use the -<tt>--enable-tai-clock</tt> option without the <tt>--enable-right-tz</tt> one. -</p> - -<p> - Be aware that setting your system clock to TAI-10 without having a -"right/" timezone will cause non-skalibs-using software to display -local time incorrectly; in such a setup, only skalibs-using software -will understand what is going on and do the proper computations to -display the correct local time. Keep your settings as consistent as -possible. -</p> - -<p> - By default, skalibs will consider you are using POSIX timezones (as well -as a UTC system clock). -</p> - <a name="usert"><h3> --enable-clock </h3></a> <p> |