ch19_03.htm

unix基础教程

<a name="unut-ch-19-sect-3.4" /><div class="sect2"><h3 class="sect2">19.3.4. Revision Numbering</h3><p>
<a name="IXT-19-123572" />
<a name="IXT-19-123573" />
<a name="IXT-19-123574" />Unless told otherwise, RCS commands typically operate on the latest revision.
Some commands have an <tt class="literal">-r</tt> option that specifies a revision number.
In addition, many options accept a revision number as an optional argument.
(In the command summary, this argument is shown as [<em class="emphasis">R</em>].)  
Revision numbers consist of up to four fields:  release, level, branch, and
sequence; but most revisions consist of only the release and level.
For example, you can check out revision 1.4 as follows:</p>
<blockquote><pre class="code"><tt class="userinput"><b>co -l -r1.4 ch01</b></tt></pre></blockquote>
<p>When you check it in again, the new revision will be marked as 1.5.
Now suppose the edited copy needs to be checked in as the next release.
You would type:</p>
<blockquote><pre class="code"><tt class="userinput"><b>ci -r2 ch01</b></tt></pre></blockquote>
<p>This creates revision 2.1.  
You can also create a branch from an earlier revision.
The following command creates revision 1.4.1.1:</p>
<blockquote><pre class="code"><tt class="userinput"><b>ci -r1.4.1 ch01</b></tt></pre></blockquote>
<p>Numbers that begin with a period are considered to be relative to
the default branch of the RCS file.  Normally, this is the
&#8220;trunk&#8221; of the revision tree.</p>
<p>Numbers are not the only way to specify revisions, though.
You can assign a text label as a revision name,
using the <tt class="literal">-n</tt> option of <tt class="literal">ci</tt> or <tt class="literal">rcs</tt>.
You can also specify this name in any option that accepts
a revision number for an argument.
For example, you could check in each of your C files,
using the same label regardless of the current revision number:</p>
<blockquote><pre class="code"><tt class="userinput"><b>ci -u -nPrototype *.c</b></tt></pre></blockquote>
<p>In addition,
you may
specify a <tt class="literal">$</tt>,
which means the revision number extracted from the keywords
of a working file.  For example:</p>
<blockquote><pre class="code"><tt class="userinput"><b>rcsdiff -r$ ch01</b></tt></pre></blockquote>
<p>compares <tt class="literal">ch01</tt> to the revision that is checked in.
You can also combine names and symbols.  The command:</p>
<blockquote><pre class="code"><tt class="userinput"><b>rcs -nDraft:$ ch*</b></tt></pre></blockquote>
<p>assigns a name to the revision numbers associated with several chapter files.</p>
</div>

<a name="unut-ch-19-sect-3.5" /><div class="sect2"><h3 class="sect2">19.3.5. Specifying the Date</h3><p>
<a name="IXT-19-123575" />
<a name="IXT-19-123576" />
<a name="IXT-19-123577" />Revisions are timestamped by time and date of check-in.
Several keyword strings include the date in their values.
Dates can be supplied in options to <tt class="literal">ci</tt>, <tt class="literal">co</tt>, and <tt class="literal">rlog</tt>.
RCS uses the following date format as its default:</p>
<blockquote><pre class="code">2000/01/10 02:00:00	<i class="lineannotation">Year/month/day  time</i></pre></blockquote>
<p>The default time zone is Greenwich Mean Time (GMT), which is also referred to
as Coordinated Universal Time (UTC).  Dates can be supplied in free format.
This lets you specify many different styles.  Here are some of
the more common ones, which show the same time as in the previous example:</p>
<blockquote><pre class="code">6:00 pm lt		<i class="lineannotation">Assuming today is Jan. 10, 2000</i>
2:00 AM, Jan. 10, 2000
Mon Jan 10 18:00:00 2000 LT	
Mon Jan 10 18:00:00 PST 2000</pre></blockquote>
<p>The uppercase or lowercase &#8220;lt&#8221; indicates local time (here, Pacific Standard
Time).  The third line shows <tt class="literal">ctime</tt> format (plus the &#8220;LT&#8221;);
the fourth line is the <tt class="literal">date</tt> command format.</p>
</div>

<a name="unut-ch-19-sect-3.6" /><div class="sect2"><h3 class="sect2">19.3.6. Specifying States</h3><p>
<a name="IXT-19-123578" />
<a name="IXT-19-123579" />In some situations, particularly programming environments,
you want to know the status of a set of revisions.
RCS files are marked by a text string that describes their <em class="emphasis">state</em>.
The default state is <tt class="literal">Exp</tt> (experimental).  Other common choices
include <tt class="literal">Stab</tt> (stable) or <tt class="literal">Rel</tt> (released).
These words are user-defined and have no special internal meaning.
Several keyword strings include the state in their values.
In addition, states can be supplied in options to 
<tt class="literal">ci</tt>, <tt class="literal">co</tt>, <tt class="literal">rcs</tt>, and <tt class="literal">rlog</tt>.</p>
</div>

<a name="unut-ch-19-sect-3.7" /><div class="sect2"><h3 class="sect2">19.3.7. Standard Options and Environment Variables</h3><p>
<a name="IXT-19-123580" />
<a name="IXT-19-123581" />
<a name="IXT-19-123582" />RCS defines an environment variable, RCSINIT,
which sets up default options for RCS commands.
If you set RCSINIT to a space-separated list of options,
they will be prepended to the command-line options
you supply to any RCS command.</p>
<p>Six options are useful to include in RCSINIT:
<tt class="literal">-q</tt>,
<tt class="literal">-V</tt>,
<tt class="literal">-V</tt><em class="emphasis">n</em>,
<tt class="literal">-T</tt>,
<tt class="literal">-x</tt>,
and
<tt class="literal">-z</tt>.
They 
can be thought of as standard options
because most RCS commands accept them.</p>
<dl><dt><tt class="literal">-q</tt>[<tt><em class="replaceable">R</em></tt>]</dt><dd>Quiet mode; don't show diagnostic output.  <em class="emphasis">R</em></tt> specifies
a file revision.</p>
</dd>
<dt><tt class="literal">-T</tt></dt><dd>If the file with the new revision has a later modification time
than that of the RCS file, update the RCS file's modification time.
Otherwise, preserve the RCS file's modification time.
This option should be used with care; see the discussion in
the <tt class="literal">ci</tt> manpage for more detail.</p>
</dd>
<dt><tt class="literal">-V</tt></dt><dd>Print the RCS version number.</p>
</dd>
<dt><tt class="literal">-V</tt><tt><em class="replaceable">n</em></tt></dt><dd>Emulate version <em class="emphasis">n</em></tt> of RCS; useful when trading files
between systems that run different versions.
<em class="emphasis">n</em> can be 3, 4, or 5.</p>
</dd>
<dt><tt class="literal">-x</tt><tt><em class="replaceable">suffixes</em></tt></dt><dd>Specify an alternate list of <em class="emphasis">suffixes</em></tt> for RCS files.
Each suffix is separated by a <tt class="literal">/</tt>.
On Unix systems, RCS files normally end with the characters <tt class="literal">,v</tt>.  
The <tt class="literal">-x</tt> option provides a workaround for systems that don't 
allow a comma character in filenames.</p>
</dd>
<dt><tt class="literal">-z</tt><tt><em class="replaceable">timezone</em></tt></dt><dd><em class="emphasis">timezone</em></tt> controls the output format for dates
in keyword substitution.
<em class="emphasis">timezone</em> should have one of the following values:
</p></dd>
</dl>

<table border="1" cellpadding="3">
<tr><th><em class="emphasis">Value</em></th><th><em class="emphasis">Effect</em></th></tr>

<tr><td><em class="emphasis">empty</em></td><td><p>Default format: UTC with no time zone and slashes separating the
parts of the date.</p>
</td></tr>
<tr><td><tt class="literal">LT</tt></td><td><p>The local time and date, in ISO-8601 format, with time-zone indication
(<em class="emphasis">YYYY</em><tt class="literal">-</tt><em class="emphasis">MM</em><tt class="literal">-</tt><em class="emphasis">DD</em>
<em class="emphasis">HH</em><tt class="literal">:</tt><em class="emphasis">MM</em><tt class="literal">:</tt><em class="emphasis">SS</em><tt class="literal">-</tt><em class="emphasis">ZZ</em>).</p>
</td></tr>
<tr><td>&#177;<em class="replaceable"><tt>hh</em><tt class="literal">:</tt><em class="replaceable">mm</tt></em></td><td><p>With a numeric offset from UTC, the output is in IS0-8601 format.</p>
</td></tr>
</table><p>

<p>For example, when depositing a working file into an RCS file, the command:</p>
<blockquote><pre class="code"><tt class="userinput"><b>ci -x,v/ ch01    </b></tt> <i class="lineannotation">Second suffix is blank</i></pre></blockquote>
<p>searches in order for the RCS filenames:</p>
<blockquote><pre class="code">RCS/ch01,v
ch01,v
RCS/ch01</pre></blockquote>
<p>RCS allows you to specify a location for temporary files.
It checks the environment variables
TMPDIR,
TMP,
and
TEMP,
in that order.
If none of those exist, it uses a default location,
such as <tt class="literal">/tmp</tt>.</p>
</div>


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