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|
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<td align="right"><i>Making TeX Work</i> Version 1.0.1
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<div class="chapter">
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<h2 class="title"><a id="chap.running"
name="chap.running"></a>Chapter 3. Running
TeX</h2>
</div>
<div>
<p class="releaseinfo">$Revision: 1.1 $</p>
</div>
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<p class="pubdate">$Date: 2002/08/23 14:31:13 $</p>
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<hr class="component-separator" />
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<p>The heart of processing a document with TeX is running<a
id="id2862591" class="indexterm" name="id2862591"></a><a
id="id2862603" class="indexterm" name="id2862603"></a> the
TeX program. In this chapter, you'll learn what happens
between the time you first start the TeX program and the time
it finishes. You'll also learn what files TeX really needs
(in addition to your document) and what to do when TeX finds
things in your document that it doesn't understand.</p>
<div class="section">
<div class="titlepage">
<div>
<h2 class="title" style="clear: both"><a
id="run.sec.formatfiles"
name="run.sec.formatfiles"></a>What Do You Run?</h2>
</div>
</div>
<p>The first thing you have to know is what program to run.
Unfortunately, the actual file you have to execute varies
between platforms and implementations. If you have built
and/or installed TeX yourself, you probably already know
what program to run. You'll have to ask your system
administrator for help if you can't figure out what the
name of the TeX executable is on your computer. The rest of
this chapter assumes that the command <tt>tex</tt> runs
TeX. You should substitute the name of the executable
program on your own system for <tt>tex</tt><a
id="id2862504" class="indexterm" name="id2862504"></a> in
the examples that follow.</p>
<p>Most implementations of TeX have some hard-coded memory
limits<a id="id2862517" class="indexterm"
name="id2862517"></a>. These limitations may cause problems
if you are trying to run a very complex document through
TeX. To combat this problem, some distributions include two
versions of the TeX executable. One version is a
“small” TeX<a id="id2862533" class="indexterm"
name="id2862533"></a><a id="id2862543" class="indexterm"
name="id2862543"></a> that generally runs faster but has
less memory available to process your documents. The other
version, a “big” TeX<a id="id2869219"
class="indexterm" name="id2869219"></a><a id="id2869229"
class="indexterm" name="id2869229"></a>, can process more
complex documents but may run more slowly. If you get a
“TeX capacity exceeded” error, and you have a
big TeX available on your system, try processing your
document with the big TeX.</p>
<p>If you still get an error, you have a document that is
simply too complex for your implementation of TeX to
handle, or you have an error in one of the macros in your
document. By examining the error log, described later in
this chapter in the section “<a
href="ch03.html#sec.logfiles" title="Log Files">the section
called “Log Files”</a>,” you can
determine what macro TeX is interpreting when the error
occurs. If the error occurs in a macro that you wrote,
check to make sure the macro functions the way you intended
by using it in a small test document.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<h2 class="title" style="clear: both"><a id="id2869278"
name="id2869278"></a>What Files Does TeX Need?</h2>
</div>
</div>
<p>Naturally, TeX needs your input file in order to process
it. However, TeX must be able to find several other files<a
id="id2869287" class="indexterm" name="id2869287"></a><a
id="id2869299" class="indexterm" name="id2869299"></a> as
well. The files that TeX needs are normally created during
the installation process. Here is a common directory layout
for TeX on a unix system:</p>
<div class="informaltable">
<table border="1">
<colgroup>
<col />
<col />
</colgroup>
<tbody>
<tr>
<td><tt>/usr/local/lib/tex/formats</tt></td>
<td>Format files</td>
</tr>
<tr>
<td><tt>/usr/local/lib/tex/pool</tt></td>
<td>Pool files</td>
</tr>
<tr>
<td><tt>/usr/local/lib/tex/formats</tt></td>
<td>Format files</td>
</tr>
<tr>
<td><tt>/usr/local/lib/tex/inputs</tt></td>
<td>“System” input files</td>
</tr>
<tr>
<td><tt>/usr/local/lib/tex/macros</tt></td>
<td>(styles, macros, and miscellaneous</td>
</tr>
<tr>
<td><tt>/usr/local/lib/tex/lib</tt></td>
<td>files distributed with TeX)</td>
</tr>
<tr>
<td><tt>/usr/local/lib/tex/ps</tt></td>
<td>PostScript support files</td>
</tr>
<tr>
<td><tt>/usr/local/lib/tex/fonts/pk</tt></td>
<td><tt>PK</tt> fonts</td>
</tr>
<tr>
<td><tt>/usr/local/lib/tex/fonts/vf</tt></td>
<td>Virtual fonts</td>
</tr>
<tr>
<td><tt>/usr/local/lib/tex/fonts/tfm</tt></td>
<td><tt>TFM</tt> metrics</td>
</tr>
</tbody>
</table>
</div>
<p>A similar layout is frequently used on other operating
systems, except that the TeX files are often stored in a
top-level directory (for example, <tt>C:$\$TEX</tt> under
MS-DOS). Because TeX is very flexible and has many
different implementations, the exact directory structure
varies. Pool files are sometimes placed in the format file
directory (which is sometimes called <tt>fmt</tt> or
<tt>fmts</tt>, rather than <tt>formats</tt>). Input files
may occur in one or more of the standard places listed
above (<tt>inputs</tt>, <tt>macros</tt>, and <tt>lib</tt>)
as well as a number of other places (<tt>texinputs</tt> is
another common name).</p>
<p>The files under the TeX tree usually come from outside
distributions, so you don't have to change them often. (You
definitely <span class="emphasis"><em>shouldn't</em></span>
put your personal macro files in that tree, even if you do
have access to it.)</p>
<p>The following sections describe, in more detail, each of
the files that TeX needs.</p>
<div class="section">
<div class="titlepage">
<div>
<h3 class="title"><a id="id2869610"
name="id2869610"></a>Pool Files</h3>
</div>
</div>
<p>Pool files contain string constants used by TeX at
runtime. Each time TeX is compiled, it creates a pool
file<a id="id2869621" class="indexterm"
name="id2869621"></a> unique to the version being
compiled. The pool file from one version of TeX will not
work with a different version.</p>
<p>In contrast to format files (discussed in the next
section), if you don't have a pool file, there's nothing
you can do about it. If you obtained precompiled programs
(from the Internet, from a friend, or commercially) and
you don't have a pool file, you received an incomplete
distribution.</p>
<p>If you did not install TeX yourself, but find that the
pool file is missing, contact the system administrator
who performed the installation. He or she did something
wrong.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<h3 class="title"><a id="id2869651"
name="id2869651"></a>Format Files</h3>
</div>
</div>
<p>As mentioned in the section “<a
href="ch01.html#sec.tex.controlsequences"
title="Boxes and Glue">the section called “Boxes
and Glue”</a>” in Chapter <a
href="ch01.html"
title="Chapter 1. The Big Picture">Chapter 1</a>,
<span class="emphasis"><em><a href="ch01.html"
title="Chapter 1. The Big Picture">Chapter 1</a></em></span>,
all of the control sequences and macros that your
document uses must be defined somewhere. One way to do
this is to use the \input command to load all of the
definitions at the beginning of each document. However,
with large macro packages like LaTeX, this process can be
very time consuming. Format files<a id="id2869699"
class="indexterm" name="id2869699"></a> are a way of
predefining control sequences and macros so they don't
have to be interpreted by TeX every time they're used. If
TeX didn't use format files, you'd have to wait for TeX
to interpret all of LaTeX every time you processed a
document that used LaTeX.</p>
<p><a id="run.sec.initexintro"
name="run.sec.initexintro"></a>Format files are created
by a special version of TeX, usually called iniTeX<a
id="id2869724" class="indexterm" name="id2869724"></a>.
Some implementations combine TeX and iniTeX into one
program. In this case, you must select iniTeX with a
special option when you run TeX. IniTeX interprets all
the control sequences in a macro package and builds the
in-memory data structures that the TeX program needs.
After loading the whole macro package, iniTeX writes the
memory image it has constructed to a format file. When
TeX later loads the format file, it simply copies it into
memory; no interpretation is necessary. This is why
loading a format file is such a fast way to define
control sequences<a id="id2869736" class="indexterm"
name="id2869736"></a>. This is also why format files are
not usually portable from one system to another,<sup>[<a
id="id2869760" name="id2869760"
href="#ftn.id2869760">25</a>]</sup> or even between
different versions of TeX on the same system. Different
versions of TeX are stored differently in memory, and
this difference in loading makes the format files
incompatible. For this reason, you need a
“big” iniTeX to make format files for a big
TeX and a “small” iniTeX for a small TeX.</p>
<p>You will find a complete discussion of macro packages
and instructions for building format files for many of
the common macro packages in Chapter <a
href="ch04.html"
title="Chapter 4. Macro Packages">Chapter 4</a>,
<span class="emphasis"><em><a href="ch04.html"
title="Chapter 4. Macro Packages">Chapter 4</a></em></span>.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<h3 class="title"><a id="sec.userfiles"
name="sec.userfiles"></a>User Files</h3>
</div>
</div>
<p>When you run TeX<a id="id2869826" class="indexterm"
name="id2869826"></a>, you have to tell it what file to
process. If you specify a complete pathname, TeX will
load the specific file that you request. For example, I
could process the document <tt>myreport.tex</tt> in the
directory <tt>/home/norm/tex/</tt> by running:</p>
<pre class="screen">
\$ <span class="bold"><b>tex /home/norm/tex/myreport</b></span>
</pre>
<p>This example applies to both unix and PC
implementations of TeX. Even though MS-DOS and OS/2
typically use the backslash to separate directory names,
<span class="emphasis"><em>always</em></span> use a
forward slash when entering filenames for TeX.</p>
<p>If you specify a simple filename without a path, TeX
looks for the file in several user-defined and, possibly,
system-defined locations. In the following example, TeX
will attempt to locate the file <tt>myreport.tex</tt> in
order to process it:</p>
<pre class="screen">
\$ <span class="bold"><b>tex myreport</b></span>
</pre>
<p>If the file <tt>myreport.tex</tt> exists in several
directories, TeX will process the first file it finds
without looking for any others. TeX always prints the
complete name of the file it processes both on the
display and in the log file, so you can always tell what
file was really processed.</p>
<p>The most common way to specify user-defined locations
is by setting the <tt>TEXINPUTS</tt> environment
variable<sup>[<a id="id2869931" name="id2869931"
href="#ftn.id2869931">26</a>]</sup> to a list of
subdirectories where TeX documents are kept. Setting
<tt>TEXINPUTS</tt> specifies where TeX should look for
<span class="emphasis"><em>documents</em></span> (files
that you input with \input or some other construct, style
files, and macros). To change where TeX looks for other
kinds of files (fonts, formats, pool files, etc.),
setting different environment variables or performing
some other customization is required. The format of the
environment variable differs according to the platform
you use. On unix systems, it is a list of directory names
separated by colons. Here is a typical example:</p>
<pre class="screen">
.:/usr/local/lib/tex/inputs:/home/norm/tex/inputs
</pre>
<p>On MS-DOS and OS/2 systems, it is a list of directory
names separated by semicolons. A typical example looks
like this:<sup>[<a id="id2869999" name="id2869999"
href="#ftn.id2869999">27</a>]</sup></p>
<pre class="screen">
.;\tex\inputs;\tex\styles;\tex\macros
</pre>
<p>Consult the documentation for your particular
implementation of TeX for more information about
system-defined locations where TeX looks for input files.
Unfortunately, this is not always well documented. For
example, an undocumented feature of version 1.4s of emTeX
always searches in the directory
<tt>\emtex\texinputs</tt> even if it does not occur in
the <tt>TEXINPUTS</tt> path. In fact, there is no way to
tell it <span class="emphasis"><em>not</em></span> to
look there, short of renaming the directory (which is
what I did).</p>
<p>If TeX cannot find a file you specify, for example
<tt>rpt-data.tex</tt>, it displays a prompt like this
one:</p>
<pre class="screen">
! I can't find file `rpt-data.tex'.
<*> \input rpt-data
Please type another input filename:
</pre>
<p>The general form of TeX error messages is discussed in
the section called “<a href="ch03.html#sec.errors"
title="What About Errors?">the section called “What
About Errors?”</a>” later in this chapter.
TeX announces an error by printing the error message on a
line that begins with an exclamation mark. Below the
error, TeX provides the context in which the error
occurred. In the example above, TeX encountered the
command \input rpt-data and tried to find the file
<tt>rpt-data.tex</tt> which it could not locate.</p>
<p>Notice that TeX automatically added the extension
<tt>.tex</tt><a id="id2870120" class="indexterm"
name="id2870120"></a> to the name of the file it was
looking for. In any context where you specify a filename,
TeX will append <tt>.tex</tt> unless you specify an
alternate extension.</p>
<p>TeX responds to a “can't find file” error
by asking you to type the name of a different file. Some
implementations of TeX allow you to abort by typing
Ctrl-C or Ctrl-D at this point,<sup>[<a id="id2870149"
name="id2870149" href="#ftn.id2870149">28</a>]</sup> but
other implementations insist that you enter a filename.
In this case, you'll find it convenient to create an
empty file called <tt>nul.tex</tt><a id="id2870165"
class="indexterm" name="id2870165"></a> in a directory in
your <tt>TEXINPUTS</tt> path so you can get around this
requirement by supplying a dummy answer to the prompt.
<tt>nul.tex</tt> is part of many standard
distributions.</p>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<h2 class="title" style="clear: both"><a
id="sec.clineopts" name="sec.clineopts"></a>The Command
Line</h2>
</div>
</div>
<p>Except for the name of a document, TeX has very few
command-line options<a id="id2870206" class="indexterm"
name="id2870206"></a>. The only option that is regularly
used is the name of a format file, but the use of this
option is frequently buried inside a batch file or shell
script.</p>
<p>It is helpful to think of TeX, LaTeX, SliTeX,
etc. as different text processors (they aren't really;
they're all TeX with different format files). This illusion
is easy to provide with shell scripts or batch files. For
example, on an MS-DOS system, you could easily have three
batch files called <tt>tex.bat</tt>, <tt>latex.bat</tt>,
and <tt>slitex.bat</tt>:</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>The <tt>tex.bat</tt> file runs the TeX executable
with the <tt>plain</tt> format file specified as an
option.</p>
</li>
<li>
<p>The <tt>latex.bat</tt> file runs TeX with the
<tt>lplain</tt> format file.</p>
</li>
<li>
<p>The <tt>slitex.bat</tt> file runs TeX with the
<tt>splain</tt> format file.</p>
</li>
</ul>
</div>
<p>Now typing <span class="bold"><b>tex <span
class="emphasis"><em>filename</em></span></b></span>
processes Plain TeX documents; typing <span
class="bold"><b>latex <span
class="emphasis"><em>filename</em></span></b></span>
processes LaTeX documents; and typing <span
class="bold"><b>slitex <span
class="emphasis"><em>filename</em></span></b></span>
processes SliTeX documents.<sup>[<a id="id2870360"
name="id2870360" href="#ftn.id2870360">29</a>]</sup> The
role of format files and macro packages is described fully
in Chapter <a href="ch04.html"
title="Chapter 4. Macro Packages">Chapter 4</a>,
<span class="emphasis"><em><a href="ch04.html"
title="Chapter 4. Macro Packages">Chapter 4</a></em></span>.</p>
<div class="section">
<div class="titlepage">
<div>
<h3 class="title"><a id="sec.runtex.cmdcautions"
name="sec.runtex.cmdcautions"></a>Command-line
Options</h3>
</div>
</div>
<p>A formal specification of the TeX command line<a
id="id2870407" class="indexterm" name="id2870407"></a>
looks like this:</p>
<div class="informalexample">
<pre class="screen">
$ tex <<span
class="emphasis"><em>switches</em></span>> <&<span
class="emphasis"><em>format</em></span>> <|<span
class="emphasis"><em>document</em></span>> <<span
class="emphasis"><em>tex-commands</em></span>>
</pre>
</div>
<p>If this looks confusing, have no fear. I'll explain
what it means in English.</p>
<p>After the name of the TeX program (or batch file), the
first things that can go on the command line are
implementation-dependent switches and options. For
example, implementations of TeX that combine iniTeX and
TeX into a single program may use <span
class="bold"><b>/I</b></span> as the switch to specify
that iniTeX processing<a id="id2870468" class="indexterm"
name="id2870468"></a> is desired (iniTeX, you may
remember, was described in the section “<a
href="ch03.html#run.sec.formatfiles"
title="What Do You Run?">the section called “What
Do You Run?”</a>,” earlier in this chapter).
There are no system-independent switches for TeX. Consult
the documentation that comes with your implementation for
more information about system-dependent switches.</p>
<p>After any system-dependent switches, the first thing
that you can put on the TeX command line is the name of
the format file<a id="id2870509" class="indexterm"
name="id2870509"></a> to use. If you specify this option,
you must include it before any other options, and you
must put an ampersand (&)<a id="id2870520"
class="indexterm" name="id2870520"></a> in front of the
format file name. If you do not specify a format file,
TeX will use a default format, usually Plain TeX.</p>
<p>After the format, TeX looks for the name of a document
to process. If TeX finds a filename on the command line,
it will process the document<a id="id2870537"
class="indexterm" name="id2870537"></a> contained in that
file before looking at any other options that may
follow.</p>
<p>Finally, you can insert arbitrary TeX commands on the
command line by typing them just as you would in a
document. The section “<a
href="ch02.html#sec.texcomp" title="Running TeX">the
section called “Running TeX”</a>” in
Chapter <a href="ch02.html"
title="Chapter 2. Editing">Chapter 2</a>,
<span class="emphasis"><em><a href="ch02.html"
title="Chapter 2. Editing">Chapter 2</a></em></span>,
describes one particular instance where this is very
useful, but it isn't something that you are likely to do
very often.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<h3 class="title"><a id="id2870602"
name="id2870602"></a>Command-line Cautions</h3>
</div>
</div>
<p>There are some special restrictions on file names used
on the command line and on the way TeX interprets the
command line. These restrictions are summarized here.</p>
<div class="section">
<div class="titlepage">
<div>
<h4 class="title"><a id="run.sec.misinterpret"
name="run.sec.misinterpret"></a>Misinterpretation
of the command line</h4>
</div>
</div>
<p>Command lines that are typed at the operating system
prompt are actually seen by your operating system's
“command processor” before they are seen by
TeX. You must be aware of special processing that might
be performed by the command processor. Under unix, for
example, the backslash<a id="id2870634"
class="indexterm" name="id2870634"></a> is frequently
interpreted as a <span class="emphasis"><em>shell
escape</em></span> character<a id="id2870656"
class="indexterm" name="id2870656"></a>, and the
ampersand<a id="id2870668" class="indexterm"
name="id2870668"></a> has another special meaning
related to job control<a id="id2870677"
class="indexterm" name="id2870677"></a>. The ampersand
is also special under some MS-DOS and OS/2 command
processors where it is the default command separation
character and will not be passed to TeX as you would
expect.</p>
<p>To insert these troublesome characters literally,
you must enclose the relevant sections of the command
line in quotation marks<a id="id2870695"
class="indexterm" name="id2870695"></a> or use some
form of shell escape mechanism. Under unix, place the
name of the format file, including the ampersand, in
double or single quotes and use two backslashes in a
row if you include TeX control sequences on the command
line. For example, type:</p>
<div class="informalexample">
<pre class="screen">
$ <span
class="bold"><b>tex '&lplain' \\nonstopmode \\input doc1</b></span>
</pre>
</div>
<p>instead of</p>
<div class="informalexample">
<pre class="screen">
$ <span
class="bold"><b>tex &lplain \nonstopmode \input doc1</b></span>
</pre>
</div>
<p>When using OS/2, place a ^ in front of an ampersand
to prevent it from being interpreted as a command
separator.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<h4 class="title"><a id="sec.runtex.texwoopts"
name="sec.runtex.texwoopts"></a>Filenames and
TeX</h4>
</div>
</div>
<p><a id="id2870772" class="indexterm"
name="id2870772"></a><a id="id2870779"
class="indexterm" name="id2870779"></a> <a
id="id2870793" class="indexterm" name="id2870793"></a>
It is easy for TeX to recognize the presence of a
format file on the command line; it must be the first
option and it must begin with an ampersand.<sup>[<a
id="id2870805" name="id2870805"
href="#ftn.id2870805">30</a>]</sup> After the format
file, TeX determines whether the next option is a file
name by looking at the first character of the option.
If the first character is not a backslash, it is a
filename; otherwise it is a TeX command, and TeX
assumes that no filename is present.</p>
<p>On some systems, notably MS-DOS and OS/2, the
backslash<a id="id2870848" class="indexterm"
name="id2870848"></a> is used to delimit the
subdirectory components of a file name. On other
systems, a forward slash is used. Regardless of the
system you use, filenames passed to TeX <span
class="emphasis"><em>must</em></span> use forward
slashes to delimit filenames.</p>
<p>For example, TeX will not process the file
<tt>letter.tex</tt> in the <tt>\tex\docs</tt> directory
of the current drive if you execute the following
command line on an MS-DOS system:</p>
<div class="informalexample">
<pre class="screen">
\$ <span class="bold"><b>tex \tex\docs\letter</b></span>
</pre>
</div>
<p>Instead, you must type the following, regardless of
the operating system you're using:</p>
<div class="informalexample">
<pre class="screen">
\$ <span class="bold"><b>tex /tex/docs/letter</b></span>
</pre>
</div>
<p>If you don't, TeX will complain that the control
sequence \tex is undefined. Even more confusing errors
may result if the first subdirectory happens to be a
valid control sequence.</p>
<p>Unfortunately, filenames containing forward slashes
are not always recognized by operating systems that use
backslashes to delimit filenames. For example, under
MS-DOS, <tt>IF EXIST C:/CONFIG.SYS</tt> returns
false,<a id="id2870956" class="indexterm"
name="id2870956"></a> even when a file called
<tt>config.sys</tt> exists in the root directory of
drive C:. Therefore, it is most convenient to use
filenames with backslashes when other commands will be
used (for example in a batch file). Filenames in batch
files must have any backslashes translated into forward
slashes before being passed to TeX. MS-DOS's command
processor isn't really powerful enough, but the task is
quite doable with JP Software<a id="id2870971"
class="indexterm" name="id2870971"></a>'s <b>4DOS</b>
command processor. <b>4DOS</b><a id="id2871000"
class="indexterm" name="id2871000"></a> is a
replacement for MS-DOS's normal command processor; it
offers many advantages over the normal processor. You
can get a shareware version of <b>4DOS</b> from many
large MS-DOS archive sites on the Internet<sup>[<a
id="id2871022" name="id2871022"
href="#ftn.id2871022">31</a>]</sup> as well as most
large bulletin board systems. The following lines,
written in <b>4DOS</b><a id="id2871048"
class="indexterm" name="id2871048"></a>'s extended
batch language, will translate all backslashes in the
environment variable <tt>TEXFN</tt> to forward
slashes:</p>
<pre class="screen">
:FixBacks
Set Count=%@Index[%TexFn,\]
If "%Count" eq "-1" Goto FixDone
Set Place=%@Eval[%Count+1]
Set TexFn=%@SubStr[%TexFn,0,%Count]/%@SubStr[%TexFn,%Place]
Goto FixBacks
:FixDone
</pre>
<p>These lines also work under OS/2 with JP Software's
<b>4OS2</b> command processor (akin to <b>4DOS</b>;
shareware versions of <b>4OS2</b> are also available).
The same task can be completed in a single line with
<b>REXX</b><a id="id2871106" class="indexterm"
name="id2871106"></a> under OS/2:</p>
<pre class="screen">
TEXFN = TRANSLATE(TEXFN, '\', '/')
</pre>
<p><b>REXX</b> is an interpreted systems-programming
language distributed with OS/2. <b>REXX</b> runs under
many other IBM operating systems in addition to OS/2.
Several versions of <b>REXX</b> are available for
MS-DOS and unix systems, too.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<h4 class="title"><a id="id2871151"
name="id2871151"></a>Multiple documents</h4>
</div>
</div>
<p>Keep in mind<a id="id2871161" class="indexterm"
name="id2871161"></a> that TeX interprets only the
first option after the format file name as a document
name. If you type the command line:</p>
<div class="informalexample">
<pre class="screen">
\$ <span class="bold"><b>tex doc1 doc2</b></span>
</pre>
</div>
<p>TeX will process only <tt>doc1.tex</tt> as a
document. The result of the above command line<a
id="id2871206" class="indexterm" name="id2871206"></a>
will be exactly as if you had typed the literal word
“doc2” at the very end of the file
<tt>doc1.tex</tt>.</p>
<p>To get TeX to process both <tt>doc1</tt> and
<tt>doc2</tt> as documents, type a command like the
following:</p>
<div class="informalexample">
<pre class="screen">
\$ <span class="bold"><b>tex doc1 \input doc2</b></span>
</pre>
</div>
<p>or, for complete clarity,</p>
<div class="informalexample">
<pre class="screen">
\$ <span class="bold"><b>tex \input doc1 \input doc2</b></span>
</pre>
</div>
<p>In either case, the structure of your document files
must allow them to be concatenated together. TeX does
not process <tt>doc1</tt> and then process
<tt>doc2</tt> separately. Instead, it processes all of
<tt>doc1</tt> and appends the text in the file
<tt>doc2</tt> directly onto the end of
<tt>doc1</tt>.</p>
</div>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<h2 class="title" style="clear: both"><a id="id2871334"
name="id2871334"></a>TeX Without Options</h2>
</div>
</div>
<p>If you run TeX without specifying any options<a
id="id2871343" class="indexterm" name="id2871343"></a> at
all, it prints out some introductory information, then
produces a <tt>**</tt> prompt<a id="id2871366"
class="indexterm" name="id2871366"></a> and stops. Here's
what emTeX's <tt>tex386</tt> produces:</p>
<pre class="screen">
This is emTeX (tex386), Version 3.141 [3c-beta8]
**
</pre>
<p>This is the only situation where the <tt>**</tt> prompt
occurs. TeX now expects you to enter text. TeX will
interpret anything you type after the <tt>**</tt> prompt
<span class="emphasis"><em>exactly</em></span> as if you
had typed it on the command line. All of the rules
regarding slashes (described in “<a
href="ch03.html#run.sec.misinterpret"
title="Misinterpretation of the command line">the section
called “Misinterpretation of the command
line”</a>” earlier) apply to commands that you
type at the <tt>**</tt> prompt. Remember, however, that
input entered at the <tt>**</tt> prompt is not seen by the
operating system, so don't use quotation marks or doubled
backslashes.</p>
<p>The last line of a document is usually a command telling
TeX that the document is finished. TeX responds by writing
the last page of the document and ending (returning control
to the operating system). If a document doesn't end with
such a command, TeX will wait for more input. When TeX runs
out of input, it displays the <tt>*</tt> prompt<a
id="id2871494" class="indexterm" name="id2871494"></a>
(single asterisk). Anything you type at the <tt>*</tt>
prompt is interpreted exactly as if it occurred in the
document that TeX was processing. You cannot specify an
alternate format or name a document at the <tt>*</tt>
prompt. You can, however, use \input to insert another
file.</p>
<p>If emTeX processes a document called
<tt>unended.tex</tt>:</p>
<pre class="screen">
% This is UNENDED.TEX
Now is the time for all good men
to come to the aid of their country.
% Note: there's no \bye command to end
% TeX's processing...
</pre>
<p>the following output appears on the terminal:</p>
<pre class="screen">
This is emTeX (tex386), Version 3.141 [3c-beta8]
**unended
(unended.tex)
*
</pre>
<p>You can exit from the TeX program at the <tt>*</tt>
prompt by telling TeX that it should stop processing the
current document. Exactly how you get out depends on the
format file you use. The following table shows the stop
commands for some TeX macro packages<a id="id2871573"
class="indexterm" name="id2871573"></a><a id="id2871590"
class="indexterm" name="id2871590"></a><a id="id2871603"
class="indexterm" name="id2871603"></a><a id="id2871616"
class="indexterm" name="id2871616"></a><a id="id2871626"
class="indexterm" name="id2871626"></a>.</p>
<div class="table">
<a id="id2871639" name="id2871639"></a>
<p class="title"><b>Table 3.1. </b></p>
<table summary="" border="1">
<colgroup>
<col align="left" />
<col align="left" />
</colgroup>
<thead>
<tr>
<th align="left">Package</th>
<th align="left">Command</th>
</tr>
</thead>
<tbody>
<tr>
<td align="left">Plain TeX</td>
<td align="left">\bye</td>
</tr>
<tr>
<td align="left">LaTeX</td>
<td align="left">\end{document}<a id="id2871705"
class="indexterm" name="id2871705"></a></td>
</tr>
<tr>
<td align="left">SliTeX</td>
<td align="left">\end{document}</td>
</tr>
<tr>
<td align="left">Lollipop</td>
<td align="left">\Stop</td>
</tr>
<tr>
<td align="left">TeXinfo</td>
<td align="left"><tt>@bye</tt></td>
</tr>
</tbody>
</table>
</div>
<p>If you do not know which format is in use, you can
almost always get out with the following steps:<sup>[<a
id="id2871781" name="id2871781"
href="#ftn.id2871781">32</a>]</sup></p>
<div class="orderedlist">
<ol type="1">
<li>
<p>Type a control sequence that TeX will not
recognize (control sequences \undefined and
\gobbledygook will work). TeX will respond with the
question mark prompt.</p>
</li>
<li>
<p>Enter <span class="bold"><b>x</b></span> at the
prompt. The question mark prompt is discussed fully
in the section “<a href="ch03.html#sec.qprompt"
title="Interpreting TeX Error Messages">the section
called “Interpreting TeX Error
Messages”</a>,” later in this
chapter.</p>
</li>
</ol>
</div>
<p>To continue the above example, if I type \undefined at
the <tt>*</tt> prompt, TeX will respond:</p>
<pre class="screen">
This is emTeX (tex386), Version 3.141 [3c-beta8]
**unended
(unended.tex)
*<span class="bold"><b>\undefined</b></span>
! Undefined control sequence.
<*> \undefined
?
</pre>
<p>If I enter <span class="bold"><b>x</b></span> at the
question mark prompt, TeX will print several informative
messages and then end, returning control to the operating
system.</p>
<pre class="screen">
This is emTeX (tex386), Version 3.141 [3c-beta8]
**unended
(unended.tex)
*\undefined
! Undefined control sequence.
<*> \undefined
? <span class="bold"><b>x</b></span>
No pages of output.
Transcript written on unended.log.
</pre>
<p>One word of caution: some macro packages redefine the
meaning of the backslash (\)<a id="id2871940"
class="indexterm" name="id2871940"></a> character so that
it doesn't function as the beginning of a control sequence
(for example, the TeXinfo format uses the at-sign,
“@”). In this case, you must precede the
undefined control sequence by the escape character, even if
it isn't the backslash.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<h2 class="title" style="clear: both"><a
id="sec.errors" name="sec.errors"></a>What About
Errors?</h2>
</div>
</div>
<p>When you write TeX documents, you will occasionally make
mistakes<a id="id2871979" class="indexterm"
name="id2871979"></a><a id="id2871992" class="indexterm"
name="id2871992"></a><a id="id2872002" class="indexterm"
name="id2872002"></a> and as a result, TeX won't be able to
process your document. There are six broad classes of
mistakes you're likely to make:</p>
<div class="orderedlist">
<ol type="1">
<li>
<p>Naming documents or files that TeX cannot
find.</p>
</li>
<li>
<p>Misspelling the name of a TeX control
sequence.</p>
</li>
<li>
<p>Failing to close an environment or forgetting to
insert a closing brace after an opening brace.</p>
</li>
<li>
<p>Using math operators outside of math mode or
forgetting to close an opened math environment.</p>
</li>
<li>
<p>Requesting a font that TeX cannot find.</p>
</li>
<li>
<p>Everything else.</p>
</li>
</ol>
</div>
<p>TeX is legitimately criticized for having error messages
that are very difficult to understand. TeX frequently
provides far more information than you really need or want,
and the excess information often obscures the actual cause
of the error.</p>
<p>Nevertheless, understanding what TeX does when it
encounters an error will help make error messages easier to
understand. Let's begin with an example. Example <a
href="ch03.html#ex.badfonttex"
title="Example 3.1. The Document BADFONT.TEX">Example 3.1</a>
shows a simple LaTeX document using the New Font Selection
Scheme (NFSS), which contains an error.<sup>[<a
id="id2872107" name="id2872107"
href="#ftn.id2872107">33</a>]</sup> The error is that the
control sequence \Large, which has been redefined to
request a 17pt font, contains a typo:
\cs[fontsize]{fontsiz} should be \fontsize.<sup>[<a
id="id2872135" name="id2872135"
href="#ftn.id2872135">34</a>]</sup></p>
<div class="example">
<a id="ex.badfonttex" name="ex.badfonttex"></a>
<p class="title"><b>Example 3.1. The Document
BADFONT.TEX</b></p>
<pre class="screen">
\documentstyle{article}
% The following definition changes the font that LaTeX
% uses for the 'Large' font. I have introduced a typo
% into the definition, “\fontsiz” should be “\fontsize”.
% The first time a \Large font is requested, an error will occur.
\renewcommand{\Large}{\fontsiz{17}{20pt}\selectfont}
\begin{document}
This text precedes the first section header.
% Note: LaTeX uses the \Large font in section
% headers...this will fail in a confusing way
% because the error is deep within the definition
% of \section where \Large is used...
\section{First Section}
This is the first and only sentence of the first section.
\end{document}
</pre>
</div>
<p>When TeX processes this file, using LaTeX with the New
Font Selection Scheme, it produces these error
messages:</p>
<pre class="screen">
This is TeX, Version 3.1415 (C version 6.1)
LaTeX Version 2.09 <25 March 1992> with NFSS2
(badfont.tex (/work/nutshell/texguide/styles/latex/article.sty
Standard Document Style `article' <14 Jan 92>.
(/work/nutshell/texguide/styles/latex/art10.sty)) (badfont.aux)
(/usr/local/lib/tex/inputs/nfss2/T1cmr.fd)
! Undefined control sequence.
\Large ->\fontsiz{17}{20pt}\selectfont
<argument> \reset@font \Large
\bf
\@sect ...x \ifdim \@tempskipa >\z@ \begingroup #6
\relax \@hangfrom {\hskip ...
l.21 \end{section}
\section{First Section}
?
</pre>
<p>These messages exemplify the kind of confusing error
messages that TeX produces. Remember the following rule:
Always look at the first and last line of the TeX error
message when trying to figure out what went wrong and where
it went wrong. In this case, the first line is:</p>
<pre class="screen">
! Undefined control sequence.
</pre>
<p>and the last line is:</p>
<pre class="screen">
l.21 \end{section}
\section{First Section}
</pre>
<p>The error is that the control sequence
\cs[fontsize]{fontsiz} is not defined and TeX was
processing line 21 of the file when it occurred.</p>
<div class="section">
<div class="titlepage">
<div>
<h3 class="title"><a id="sec.logfiles"
name="sec.logfiles"></a>Log Files</h3>
</div>
</div>
<p>You don't have to remember or write down the error
messages that TeX produces. When TeX processes a
document, it produces a transcript<a id="id2872267"
class="indexterm" name="id2872267"></a> of everything
that occurs; you can refer to this transcript later if
you need to recall what errors occurred when you
processed your document. TeX stores this transcript in a
file which has the same name as the document and the
extension <tt>.log</tt>. For example, if you process
<tt>main.tex</tt>, TeX produces a transcript in
<tt>main.log</tt>.</p>
<div class="note"
style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
<p>Log files go in the current directory. TeX always
places the log file in the current directory, even if
you specify a path when you format your document. For
example, if you process <tt>lectures/main.tex</tt>, TeX
produces a transcript in <tt>main.log</tt>, not in
<tt>lectures/main.log</tt> as you might expect.</p>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<h3 class="title"><a id="sec.qprompt"
name="sec.qprompt"></a>Interpreting TeX Error
Messages</h3>
</div>
</div>
<p>The first line of a TeX error message begins with an
exclamation point followed by the text of the message<a
id="id2872354" class="indexterm" name="id2872354"></a>.
The lines that follow it show the context in which the
error occurred.<sup>[<a id="id2872367" name="id2872367"
href="#ftn.id2872367">35</a>]</sup> In the previous
example, the error message indicates an <tt>Undefined
control sequence</tt>. This means that TeX encountered a
control sequence which was not previously defined.</p>
<p>The final line, which says <tt>l.21 \section{First
Section}</tt>, occurs right above the question mark
prompt. It identifies the line in your document that TeX
was processing when it encountered the error. The error
occurred when TeX was at line 21 of the file, and that
line began with <tt>\section{First Section}</tt>.</p>
<p>Between the first and last lines, TeX prints a
detailed description of how the error occurred. This is
necessary because the error may have occurred inside the
replacement text of a macro that you used. When TeX
encounters a control sequence, like \section, it has to
look up the definition to figure out how to typeset your
document. The definition of a control sequence may
contain other control sequences which also have to be
interpreted. It is possible for TeX to be several levels
deep, as it was in this case, when an error occurs. To
give the person who wrote the definition of the control
sequence an opportunity to figure out what went wrong,
TeX prints out a <span class="emphasis"><em>trace
back</em></span><a id="id2872434" class="indexterm"
name="id2872434"></a> of what happened before the error.
As you gain experience with a particular macro package,
you'll find the intervening lines more meaningful.</p>
<p>Correcting an error depends entirely on the nature of
the error. In this case, all you need to do is correct
the typo.</p>
<p>As stated above, there are six general classes of
errors you might encounter when you run TeX. The
following sections briefly describe each class.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<h3 class="title"><a id="id2872461"
name="id2872461"></a>Naming a File TeX Cannot
Find</h3>
</div>
</div>
<p>Missing documents are discussed in the section called
“<a href="ch03.html#sec.userfiles"
title="User Files">the section called “User
Files”</a>,” earlier in this chapter.</p>
<p>If you request a format file<a id="id2872489"
class="indexterm" name="id2872489"></a> that cannot be
found, TeX issues the following warning message:</p>
<pre class="screen">
Sorry, I can't find that format; will try the default
</pre>
<p>TeX then attempts to typeset your document with Plain
TeX.<sup>[<a id="id2872514" name="id2872514"
href="#ftn.id2872514">36</a>]</sup> To correct this
problem, run TeX with the correct format file name. If
the format file isn't available, you will have to build
it. Chapter <a href="ch04.html"
title="Chapter 4. Macro Packages">Chapter 4</a>,
<span class="emphasis"><em><a href="ch04.html"
title="Chapter 4. Macro Packages">Chapter 4</a></em></span>,
describes how to build format files for several common
macro packages.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<h3 class="title"><a id="id2872549"
name="id2872549"></a>Misspelling a Control Sequence
Name</h3>
</div>
</div>
<p>Misspelling a control sequence name<a id="id2872558"
class="indexterm" name="id2872558"></a> is one of the
most common errors. For example, you might type
\ipnut{chap1} in your document instead of \input{chap1}.
The solution is straightforward and usually easy to
identify. In many cases, you can simply proceed after
encountering this error. Although TeX may not typeset
your document correctly, you can continue to look for
other errors. The section called “<a
href="ch03.html#sec.qprompt"
title="Interpreting TeX Error Messages">the section
called “Interpreting TeX Error
Messages”</a>,” later in this chapter,
describes how to continue after an error.</p>
<p>In some cases, TeX may become badly confused by a
misspelled control sequence name, in which case you
should give up and fix the spelling error before trying
to process your document further. This may happen if you
misspell a LaTeX environment name (\begin{itemze} instead
of \begin{itemize}, for example),<sup>[<a id="id2872615"
name="id2872615" href="#ftn.id2872615">37</a>]</sup>
which will make LaTeX misinterpret many of the control
sequences which follow.</p>
<p>Sometimes TeX will complain that a control sequence is
undefined when you <span
class="emphasis"><em>know</em></span> that the control
sequence is spelled correctly. When this occurs, make
sure that you are using the correct format file (see the
section “<a href="ch03.html#sec.clineopts"
title="The Command Line">the section called “The
Command Line”</a>” earlier in this chapter),
loading the correct macro files, and using the correct
style options.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<h3 class="title"><a id="id2872653"
name="id2872653"></a>Failure to Close an
Environment</h3>
</div>
</div>
<p>Failure to close an environment<a id="id2872662"
class="indexterm" name="id2872662"></a> is another very
common error. There are several distinct errors in this
category:</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>Failure to insert a closing brace (<tt>}</tt>)
for each opening brace may cause a “TeX
capacity exceeded” error when TeX processes
your document. This happens because sometimes TeX
tries to read everything between braces into
memory. If the closing brace is absent, TeX may run
out of memory.</p>
<p>If the braces are supposed to enclose the
argument to a macro, you may also get this error:<a
id="id2872709" class="indexterm"
name="id2872709"></a></p>
<pre class="screen">
! Paragraph ended before <span
class="emphasis"><em>macro</em></span> was complete.
</pre>
<p>In order to help detect errors of this type, TeX
doesn't ordinarily allow the argument of a macro to
consist of more than one paragraph, so the first
blank line after the place where you failed to type
the closing brace may produce this error.</p>
</li>
<li>
<p>Failure to close a begin/end environment pair
causes LaTeX to complain about a mismatch when it
encounters the next
\end{\texttt{<i><tt>environment</tt></i>}}
command.<a id="id2872764" class="indexterm"
name="id2872764"></a></p>
</li>
<li>
<p>If your document ends with an open environment,
TeX will warn you that:</p>
<pre class="screen">
! (\end occurs inside a group at level <span
class="emphasis"><em>n</em></span>)
</pre>
<p>where <tt><i><tt>n</tt></i></tt> is the number
of open groups, usually 1.</p>
</li>
<li>
<p>Failure to close a mathematics environment will
result in the error:</p>
<pre class="screen">
! Missing $ inserted
</pre>
<p>when TeX reaches a macro that does not make
sense in mathematics mode (like \section) or when a
surrounding group ends.</p>
</li>
</ul>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<h3 class="title"><a id="id2872844"
name="id2872844"></a>Math Outside of Math Mode</h3>
</div>
</div>
<p>TeX has a lot of operators for special treatment of
mathematical formulas. These operators must occur inside
<span class="emphasis"><em>mathematics mode</em></span><a
id="id2872858" class="indexterm" name="id2872858"></a>,<a
id="id2872867" class="indexterm" name="id2872867"></a>
which is usually delimited by dollar signs in your
document.<a id="id2872879" class="indexterm"
name="id2872879"></a></p>
<p>If you attempt to use math operators, superscripts,
subscripts, or other math-mode control sequences outside
of mathematics mode, the following error will occur:<a
id="id2872899" class="indexterm"
name="id2872899"></a></p>
<pre class="screen">
! Missing $ inserted
</pre>
<p>This is your clue that a mathematics environment has
not been closed properly or that you failed to open one
before using a math-mode operator.</p>
<p>For example, the underscore character is usually
defined to be a math-mode operator which starts a
subscript, in other words <tt>H${}_2$O</tt> produces
“H${}_2$O” in your document.<sup>[<a
id="id2872944" name="id2872944"
href="#ftn.id2872944">38</a>]</sup> If you use the
underscore outside of mathematics mode, such as in
regular text:</p>
<pre class="screen">
The file “test_one” contains the ...
</pre>
<p>TeX will respond:</p>
<pre class="screen">
! Missing $ inserted
<inserted text>
$
<to be read again>
_
The file “test_
one” contains the ...
?
</pre>
<p>In LaTeX, the easiest way around this problem is to
enclose the offending text in a “verbatim”
macro, like this:</p>
<pre class="screen">
The file “<tt>test_one</tt>” contains the ...
</pre>
<p>Note that the argument to the <tt>macro</tt>is
delimited by any two identical characters (in this case,
two “<tt>+</tt>” signs).</p>
<p>In Plain TeX or another format, the problem can be
circumvented in similar ways; consult the reference for
the format you are using. Also consult Table <a
href="ch01.html#tab.acttype"
title="Table 1.2. How to Typeset Special Characters">
Table 1.2</a> in Chapter <a href="ch01.html"
title="Chapter 1. The Big Picture">Chapter 1</a>,
<span class="emphasis"><em><a href="ch01.html"
title="Chapter 1. The Big Picture">Chapter 1</a></em></span>,
for a list of special characters and how to type them in
your documents.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<h3 class="title"><a id="id2873082"
name="id2873082"></a>Missing Fonts</h3>
</div>
</div>
<p>The first<a id="id2873090" class="indexterm"
name="id2873090"></a> time that you use each font, TeX
loads font metric information about the font. The font
metric information, stored in a <tt>TFM</tt> file,
includes information about the sizes of each character as
well as kerning and ligature information. These topics
are discussed fully in Chapter <a href="ch05.html"
title="Chapter 5. Fonts">Chapter 5</a>,
<span class="emphasis"><em><a href="ch05.html"
title="Chapter 5. Fonts">Chapter 5</a></em></span>.</p>
<p>If you request a font that does not exist, for example
<tt>crm10</tt> (a misspelling of <tt>cmr10</tt>), TeX
cannot find a <tt>TFM</tt> file for the font and
therefore displays:</p>
<pre class="screen">
Font \myfont=crm10 not loadable: Metric (TFM) file not found
</pre>
<p>This means that TeX attempted to associate the font
described by the <tt>TFM</tt> file <tt>crm10.tfm</tt>
with the control sequence \myfont, but the <tt>TFM</tt>
file didn't exist. You must have a <tt>TFM</tt> file for
every font that you use.</p>
<p>A second kind of error---actually, a warning---occurs
when you are using the New Font Selection Scheme (NFSS)<a
id="id2873221" class="indexterm" name="id2873221"></a>.
The NFSS performs font substitution, if possible, when an
unknown font is requested. The NFSS is described in
Chapter <a href="ch04.html"
title="Chapter 4. Macro Packages">Chapter 4</a>,
<span class="emphasis"><em><a href="ch04.html"
title="Chapter 4. Macro Packages">Chapter 4</a></em></span>,
in the “<a href="ch04.html#sec.latex"
title="LaTeX">the section called
“LaTeX”</a>” section.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<h3 class="title"><a id="id2873273"
name="id2873273"></a>Everything Else</h3>
</div>
</div>
<p>There are, unfortunately, lots of other errors that
can occur. Some of the errors are directly related to TeX
while others are warning and error messages associated
with particular macro packages. There is no way to
catalog every one of them or suggest what can be done in
every case.</p>
<p>The best advice I can offer is to isolate the problem
in as small a document as possible, consult the
references you have available very carefully, and, if all
else fails, forward your problem to one of the electronic
forums that deal with TeX (the <tt>Info-TeX</tt> mailing
list<a id="id2873302" class="indexterm"
name="id2873302"></a> and the <tt>comp.text.tex</tt>
newsgroup<a id="id2873326" class="indexterm"
name="id2873326"></a>, for example).</p>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<h2 class="title" style="clear: both"><a id="id2873346"
name="id2873346"></a>The Question Mark Prompt</h2>
</div>
</div>
<a id="id2873352" class="indexterm" name="id2873352"></a>
<p>When TeX encounters an error, it displays an error
message and a summary of the error, as described in the
section called “<a href="ch03.html#sec.errors"
title="What About Errors?">the section called “What
About Errors?”</a>” earlier in this chapter.
Following the error, TeX normally stops and displays the
question mark prompt.</p>
<p>If you type a question mark of your own at the prompt,
TeX displays the actions available to you:</p>
<pre class="screen">
? ?
Type <return> to proceed,
S to scroll future error messages,
R to run without stopping, Q to run quietly,
I to insert something, E to edit your file,
1 or ... or 9 to ignore the next 1 to 9 tokens
of input, H for help, X to quit.
?
</pre>
<p>You can type any of the following responses at the
question mark prompt:<a id="id2873401" class="indexterm"
name="id2873401"></a></p>
<div class="variablelist">
<dl>
<dt><span class="term">Type <b>Return</b> to
proceed.</span></dt>
<dd>
<p>Simply typing Return will cause TeX to ignore the
error and proceed. Depending on the nature of the
error, this may cause more errors immediately or
later on.</p>
</dd>
<dt><span class="term">Type <b>S</b> to scroll future
error messages.</span></dt>
<dd>
<p>Typing <b>S</b> tells TeX to continue and not to
stop for most future errors. TeX will continue to
print the error messages, both to the terminal and to
the log file, but it will not display the question
mark prompt again.</p>
<p>TeX will still stop and ask about missing
files.</p>
</dd>
<dt><span class="term">Type <b>R</b> to run without
stopping.</span></dt>
<dd>
<p>The <b>R</b> option is just like <b>S</b> except
that it tells TeX to ignore missing files as well.
TeX will proceed blindly forward as best as it can.
You will still see all of the error messages scroll
by as TeX proceeds.</p>
</dd>
<dt><span class="term">Type <b>Q</b> to run
quietly.</span></dt>
<dd>
<p>This option is just like <b>R</b> except that
error messages are not displayed on the screen. The
messages are saved in the log file, however, even
though they are not displayed.</p>
</dd>
<dt><span class="term">Type <b>I</b> to insert
something.</span></dt>
<dd>
<p>If you notice a simple typo, you can correct it
with the <b>I</b> command. For example, suppose that
TeX complains of an undefined control sequence:
\cte{kn:art1}. You recognize that this should have
been \cite{kn:art1}. You can insert the correct
control sequence by responding <tt>i\cite</tt> to the
question mark prompt. TeX will ignore the misspelled
control sequence and insert the (correct) sequence
\cite in its place.</p>
<p>Inserting words or commands at the question mark
prompt <span class="emphasis"><em>does
not</em></span> change your input file. It simply
instructs TeX to <span
class="emphasis"><em>pretend</em></span> that your
file contained a different sequence of words and
commands. You must change the input file with an
editor, or the same error will occur the next time
you format the document.</p>
</dd>
<dt><span class="term">Type <b>E</b> to edit your
file.</span></dt>
<dd>
<p>This option terminates TeX. If your system is
configured appropriately, an editor will be loaded
automatically, and the cursor will be placed at the
offending line in your input file. This is not
possible in all environments.</p>
</dd>
<dt><span class="term">Type <b><i><tt>n</tt></i></b>,
where <i><tt>n</tt></i> is a number between 1 and
9.</span></dt>
<dd>
<p>This option tells TeX to ignore some of the input.
After skipping over the number of <span
class="emphasis"><em>tokens</em></span> you request,
TeX returns to the question mark prompt so that you
can delete more tokens.</p>
<p>What's a token<a id="id2873692" class="indexterm"
name="id2873692"></a>? When TeX reads an input file,
it breaks each line down into the smallest,
indivisible chunks that have meaning. These are
called tokens. For the most part, tokens are
individual characters. The exceptions are control
sequences<a id="id2873705" class="indexterm"
name="id2873705"></a>, which are single tokens, and
white spaces which are also single tokens. There
<span class="emphasis"><em>are</em></span> other
exceptions (and more technical definitions of
“token”), but that's the gist of it.</p>
</dd>
<dt><span class="term">Type <b>H</b> for
help.</span></dt>
<dd>
<p>Typing <b>H</b> displays a slightly more verbose
description of the error that occurred and, usually,
suggests the nature of the corrective action that you
might take.</p>
</dd>
<dt><span class="term">Type <b>X</b> to
quit.</span></dt>
<dd>
<p>Typing <b>X</b> tells TeX to stop immediately and
ends the TeX program. If there are any completed
pages (pages processed before the error, in other
words), they are written to the <tt>DVI</tt> file
before TeX ends.</p>
</dd>
</dl>
</div>
</div>
<div class="footnotes">
<br />
<hr width="100" align="left" />
<div class="footnote">
<p><sup>[<a id="ftn.id2869760" name="ftn.id2869760"
href="#id2869760">25</a>]</sup> {The exception occurs in
some unix versions of TeX where provisions are made for
different architectures to share the same format files.
The exact same version of TeX must be running on both
architectures for this to work.}</p>
</div>
<div class="footnote">
<p><sup>[<a id="ftn.id2869931" name="ftn.id2869931"
href="#id2869931">26</a>]</sup> {The exact name of the
environment variable<a id="id2869936" class="indexterm"
name="id2869936"></a><a id="id2869947" class="indexterm"
name="id2869947"></a> differs between
implementations.}</p>
</div>
<div class="footnote">
<p><sup>[<a id="ftn.id2869999" name="ftn.id2869999"
href="#id2869999">27</a>]</sup> You will notice that I've
used backslashes<a id="id2870004" class="indexterm"
name="id2870004"></a> to separate directory components in
the path. Environment variables are handled by the
system-dependent portions of TeX, so it's okay to use
backslashes here. You can also use forward slashes, but I
use backslashes because that is more typical of MS-DOS
and OS/2 environments.</p>
</div>
<div class="footnote">
<p><sup>[<a id="ftn.id2870149" name="ftn.id2870149"
href="#id2870149">28</a>]</sup> {MS-DOS and OS/2
implementations of TeX may use Ctrl-Z (possibly followed
by a carriage return) instead of Ctrl-C or Ctrl-D.}</p>
</div>
<div class="footnote">
<p><sup>[<a id="ftn.id2870360" name="ftn.id2870360"
href="#id2870360">29</a>]</sup> {On unix systems, the
same effect is often achieved with symbolic links. Most
unix implementations look for different standard format
files based upon the name of the executable that starts
them.}</p>
</div>
<div class="footnote">
<p><sup>[<a id="ftn.id2870805" name="ftn.id2870805"
href="#id2870805">30</a>]</sup> {In the unlikely event
that you have a TeX document stored in a file with a name
beginning with an ampersand, use the following trick to
process that file: instead of running <b>tex
&file</b>, run <b>tex \input &file</b> (or even
<b>tex &format \input &file</b>).</p>
</div>
<div class="footnote">
<p><sup>[<a id="ftn.id2871022" name="ftn.id2871022"
href="#id2871022">31</a>]</sup> {For example,
<tt>oak.oakland.edu</tt> in the directory
<tt>/pub/msdos/4DOS</tt>.}</p>
</div>
<div class="footnote">
<p><sup>[<a id="ftn.id2871781" name="ftn.id2871781"
href="#id2871781">32</a>]</sup> {Typing the break
character (<b>Ctrl-C</b> or <b>Ctrl-Break</b>, for
example) sometimes works as well, but some
implementations of TeX don't respond to the break
character at every prompt. On unix systems, use
<b>Ctrl-D</b>. EmTeX responds to <b>Ctrl-Z</b> followed
by <b>Return</b>.}</p>
</div>
<div class="footnote">
<p><sup>[<a id="ftn.id2872107" name="ftn.id2872107"
href="#id2872107">33</a>]</sup> {The details of LaTeX and
the NFSS are discussed in Chapter <a
href="ch04.html"
title="Chapter 4. Macro Packages">Chapter 4</a>,
<span class="emphasis"><em><a href="ch04.html"
title="Chapter 4. Macro Packages">Chapter 4</a></em></span>.
It is simply convenient to use a concrete example in this
case. Do not be concerned if you do not use LaTeX or the
NFSS.}</p>
</div>
<div class="footnote">
<p><sup>[<a id="ftn.id2872135" name="ftn.id2872135"
href="#id2872135">34</a>]</sup> {In practice, redefining
a control sequence like $\$<tt>Large</tt> in a document
is a bad idea. I've done it here only to provide an
example of an error that occurs inside another
macro.}</p>
</div>
<div class="footnote">
<p><sup>[<a id="ftn.id2872367" name="ftn.id2872367"
href="#id2872367">35</a>]</sup> {The number of lines of
context shown in the error message is determined by the
value of the built-in parameter
$\$<tt>errorcontextlines</tt>.}</p>
</div>
<div class="footnote">
<p><sup>[<a id="ftn.id2872514" name="ftn.id2872514"
href="#id2872514">36</a>]</sup> {It is possible to make
other formats the default, but in practice I've never
seen it done.}</p>
</div>
<div class="footnote">
<p><sup>[<a id="ftn.id2872615" name="ftn.id2872615"
href="#id2872615">37</a>]</sup> Technically, LaTeX
environment names are not a control sequence names, but
they behave in very much the same way in LaTeX.</p>
</div>
<div class="footnote">
<p><sup>[<a id="ftn.id2872944" name="ftn.id2872944"
href="#id2872944">38</a>]</sup> {The empty curly braces
are necessary in this example because otherwise there
wouldn't be anything in front of the subscript command
for TeX to subscript below. Typically, another digit or
symbol would come in front of the subscript command. In
this case, I didn't want the “H” and
“O” in the math environment because letters
are printed in math-italics in math mode.}</p>
</div>
</div>
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