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<html><head><title>Predefined Registers (UNIX in a Nutshell: System V Edition)</title><link rel="stylesheet" type="text/css" href="../style/style1.css" /><meta name="DC.Creator" content="Arnold Robbins" /><meta name="DC.Format" content="text/xml" scheme="MIME" /><meta name="DC.Language" content="en-US" /><meta name="DC.Publisher" content="O'Reilly & Associates, Inc." /><meta name="DC.Source" scheme="ISBN" content="1-56592-427-4" /><meta name="DC.Subject.Keyword" content="stuff" /><meta name="DC.Title" content="UNIX in a Nutshell: System V Edition" /><meta name="DC.Type" content="Text.Monograph" /></head><body bgcolor="#ffffff"><img src="gifs/smbanner.gif" usemap="#banner-map" border="0" alt="Book Home" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Book Title" /><area shape="rect" coords="629,-11,726,25" href="jobjects/fsearch.htm" alt="Search this book" /></map><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch12_07.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228" /><td align="right" valign="top" width="228"><a href="ch12_09.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr></table></div><h2 class="sect1">12.8. Predefined Registers</h2><p><a name="IXT-12-123401" /><a name="IXT-12-123402" /><a name="IXT-12-123403" />There are two types of predefined registers: read-only and read-write.These are all accessed via the <tt class="literal">\n</tt> escape sequence,even though some of them actually return string values.</p><a name="unut-ch-12-sect-8.1" /><div class="sect2"><h3 class="sect2">12.8.1. Read-Only Registers</h3><table border="1" cellpadding="3"><tr><td><tt class="literal">.$</tt></td><td><p>Number of arguments available at the current macro level.</p></td></tr><tr><td><tt class="literal">$$</tt></td><td>Process ID of <tt class="literal">troff</tt> process (<tt class="literal">ditroff</tt> only).</td></tr><tr><td><tt class="literal">.A</tt></td><td><p>Set to 1 in <tt class="literal">troff</tt>,if <tt class="literal">-a</tt> option used; always 1 in <tt class="literal">nroff</tt>.</p></td></tr><tr><td><tt class="literal">.F</tt></td><td><p>Name of the current input file(recent <tt class="literal">ditroff</tt> only).</p></td></tr><tr><td><tt class="literal">.H</tt></td><td>Available horizontal resolution in basic units.</td></tr><tr><td><tt class="literal">.L</tt></td><td><p>Current line spacing (set by <tt class="literal">.ls</tt>) value(recent <tt class="literal">ditroff</tt> only).</p></td></tr><tr><td><tt class="literal">.R</tt></td><td><p>Number of unused number registers(recent <tt class="literal">ditroff</tt> only).</p></td></tr><tr><td><tt class="literal">.T</tt></td><td><p>Set to 1 in <tt class="literal">nroff</tt>, if <tt class="literal">-T</tt> option used;always 0 in <tt class="literal">oroff</tt>;in <tt class="literal">ditroff</tt>, the string <tt class="literal">\*(.T</tt> containsthe value of <tt class="literal">-T</tt>.</p></td></tr><tr><td><tt class="literal">.V</tt></td><td>Available vertical resolution in basic units.</td></tr><tr><td><tt class="literal">.a</tt></td><td><p>Post-line extra line space most recently utilized using <tt class="literal">\x'</tt><em class="replaceable"><tt>n</tt></em><tt class="literal">'</tt>.</p></td></tr><tr><td><tt class="literal">.b</tt></td><td><p>Emboldening level (recent <tt class="literal">ditroff</tt> only).</p></td></tr><tr><td><tt class="literal">.c</tt></td><td>Number of lines read from current input file.</td></tr><tr><td><tt class="literal">.d</tt></td><td><p>Current vertical place in current diversion;equal to register <tt class="literal">nl</tt> whenthere is no diversion.</p></td></tr><tr><td><tt class="literal">.f</tt></td><td><p>Current font as number (1 to 4 in <tt class="literal">otroff</tt>;1 to 99 in <tt class="literal">ditroff</tt>).</p></td></tr><tr><td><tt class="literal">.h</tt></td><td>Text baseline high-water mark on current page or diversion.</td></tr><tr><td><tt class="literal">.i</tt></td><td>Current indent.</td></tr><tr><td><tt class="literal">.j</tt></td><td>Current adjustment mode.</td></tr><tr><td><tt class="literal">.k</tt></td><td><p>Current <em class="emphasis">output</em> horizontal position.</p></td></tr><tr><td><tt class="literal">.l</tt></td><td>Current line length.</td></tr><tr><td><tt class="literal">.n</tt></td><td>Length of text portion on previous output line.</td></tr><tr><td><tt class="literal">.o</tt></td><td>Current page offset.</td></tr><tr><td><tt class="literal">.p</tt></td><td>Current page length.</td></tr><tr><td><tt class="literal">.s</tt></td><td>Current point size.</td></tr><tr><td><tt class="literal">.t</tt></td><td>Distance to the next trap.</td></tr><tr><td><tt class="literal">.u</tt></td><td>Equal to 1 in fill mode and 0 in no-fill mode.</td></tr><tr><td><tt class="literal">.v</tt></td><td>Current vertical line spacing.</td></tr><tr><td><tt class="literal">.w</tt></td><td>Width of previous character.</td></tr><tr><td><tt class="literal">.x</tt></td><td>Reserved version-dependent register.</td></tr><tr><td><tt class="literal">.y</tt></td><td>Reserved version-dependent register.</td></tr><tr><td><tt class="literal">.z</tt></td><td>Name of current diversion.</td></tr></table><p></div><a name="unut-ch-12-sect-8.2" /><div class="sect2"><h3 class="sect2">12.8.2. Read-Write Registers</h3><table border="1" cellpadding="3"><tr><td><tt class="literal">%</tt></td><td>Current page number.</td></tr><tr><td><tt class="literal">ct</tt></td><td><p>Character type (set by <tt class="literal">\w</tt> function).</p></td></tr><tr><td><tt class="literal">dl</tt></td><td>Width (maximum) of last completed diversion.</td></tr><tr><td><tt class="literal">dn</tt></td><td>Height (vertical size) of last completed diversion.</td></tr><tr><td><tt class="literal">dw</tt></td><td>Current day of the week (1 to 7).</td></tr><tr><td><tt class="literal">dy</tt></td><td>Current day of the month (1 to 31).</td></tr><tr><td><tt class="literal">hp</tt></td><td><p>Current horizontal place on <em class="emphasis">input</em> line.</p></td></tr><tr><td><tt class="literal">ln</tt></td><td>Output line number.</td></tr><tr><td><tt class="literal">mo</tt></td><td>Current month (1 to 12).</td></tr><tr><td><tt class="literal">nl</tt></td><td>Vertical position of last printed text baseline.</td></tr><tr><td><tt class="literal">sb</tt></td><td><p>Depth of string below baseline(generated by <tt class="literal">\w</tt> function).</p></td></tr><tr><td><tt class="literal">st</tt></td><td><p>Height of string above baseline(generated by <tt class="literal">\w</tt> function).</p></td></tr><tr><td><tt>yr</tt></td><td><p>Years since 1900.<a href="#footnote-2">[2]</a>Yes, there's a potential Y2K problem here.</td></tr></table><p><a name="footnote-2">[2] This will be <literal>100</literal> in 2000.</a></p></div><p><hr width="684" align="left" /><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch12_07.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228"><a href="index.htm"><img src="../gifs/txthome.gif" alt="Home" border="0" /></a></td><td align="right" valign="top" width="228"><a href="ch12_09.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr><tr><td align="left" valign="top" width="228">12.7. Escape Sequences</td><td align="center" valign="top" width="228"><a href="index/index.htm"><img src="../gifs/index.gif" alt="Book Index" border="0" /></a></td><td align="right" valign="top" width="228">12.9. Special Characters</td></tr></table></div><hr width="684" align="left" /><img src="../gifs/navbar.gif" usemap="#library-map" border="0" alt="Library Navigation Links" /><p><p><font size="-1"><a href="copyrght.htm">Copyright © 2003</a> O'Reilly & Associates. 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