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<h4 class="subsection" id="Breaking-1">5.1.4 Breaking</h4>
<a class="index-entry-id" id="index-break"></a>
<a class="index-entry-id" id="index-implicit-line-break"></a>
<a class="index-entry-id" id="index-line-break_002c-output"></a>
<a class="index-entry-id" id="index-output-line-break"></a>
<p>Once an output line is full, the next word (or remainder of a hyphenated
one) is placed on a different output line; this is called a <em class="dfn">break</em>.
In this manual and in <code class="code">roff</code> discussions generally, a “break” if
not further qualified always refers to the termination of an output
line. When the formatter is filling text, it introduces breaks
automatically to keep output lines from exceeding the configured line
length. After an automatic break, GNU <code class="code">troff</code> adjusts the line if
applicable (see below), and then resumes collecting and filling text on
the next output line.
</p>
<p>Sometimes, a line cannot be broken automatically. This usually does
not happen with natural language text unless the output line length has
been manipulated to be extremely short, but it can with specialized
text like program source code. We can use <code class="code">perl</code> at the shell
prompt to contrive an example of failure to break the line. We also
employ the <samp class="option">-z</samp> option to suppress normal output.
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">$ perl -e 'print "#" x 80, "\n";' | nroff -z
error→ warning: cannot break line
</pre></div></div>
<p>The remedy for these cases is to tell GNU <code class="code">troff</code> where the line
may be broken without hyphens. This is done with the non-printing break
point escape sequence ‘<samp class="samp">\:</samp>’; see <a class="ref" href="Manipulating-Hyphenation.html">Manipulating Hyphenation</a>.
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<p>What if the document author wants to stop filling lines temporarily, for
instance to start a new paragraph? There are several solutions. A
blank input line not only causes a break, but by default it also outputs
a one-line vertical space (effectively a blank output line). This
behavior can be modified; see <a class="ref" href="Blank-Line-Traps.html">Blank Line Traps</a>. Macro packages
may discourage or disable the blank line method of paragraphing in favor
of their own macros.
</p>
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<a class="index-entry-id" id="index-spaces_002c-leading-and-trailing"></a>
<a class="index-entry-id" id="index-trailing-spaces-on-text-lines"></a>
<a class="index-entry-id" id="index-leading-space-macro-_0028lsm_0029"></a>
<p>A line that begins with one or more spaces causes a break. The spaces
are output at the beginning of the next line without being
<em class="emph">adjusted</em> (see below); however, this behavior can be modified
(see <a class="pxref" href="Leading-Space-Traps.html">Leading Space Traps</a>). Again, macro packages may provide other
methods of producing indented paragraphs. Trailing spaces on text lines
are discarded.<a class="footnote" id="DOCF23" href="groff.html_fot.html#FOOT23"><sup>23</sup></a>
</p>
<p>What if the file ends before enough words have been collected to fill an
output line? Or the output line is exactly full but not yet broken, and
there is no more input? GNU <code class="code">troff</code> interprets the end of input as
a break. Certain requests also cause breaks, implicitly or explicitly.
This is discussed in <a class="ref" href="Manipulating-Filling-and-Adjustment.html">Manipulating Filling and Adjustment</a>.
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