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<th colspan="3" align="center">LPRng Reference Manual: 24
Sep 2004 (For LPRng-3.8.28)</th>
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<h1 class="SECT1"><a name="SAFECHARS">6.12. Fixing Bad
Control Files and Metacharacters</a></h1>
<p>Options used:</p>
<ul>
<li>
<p><var class="LITERAL">safe_chars=</var><span class=
"emphasis"><i class="EMPHASIS">additional safe characters
for control file</i></span></p>
</li>
</ul>
<br>
<br>
<p>RFC1179 defines a simple protocol and standard for print
jobs to be interchanged between print spooling systems.
Unfortunately, there were some major mistakes in not
specifying the exact form that text would take when placed in
the control file.</p>
<p>By default, <b class="APPLICATION">LPRng</b> will brutally
convert a non-conforming RFC1179 control file into one that
is acceptable to most, if not all, existing RFC1179
implementations. In order to prevent problems with <b class=
"APPLICATION">LPRng</b> ruthlessly purges all characters but
upper and lower case letters, spaces, tabs, and <var class=
"LITERAL">-_.@/:()=,+-%</var> from the control file,
replacing suspicious characters with underscore (<var class=
"LITERAL">_</var>). In addition, <b class=
"APPLICATION">LPRng</b> will ruthlessly regenerate control
file entries and data file names so that they are compliant
with all known RFC1179 implementations.</p>
<p>For some installations, the default set of safe characters
may be overly restrictive. For example, <span class=
"emphasis"><i class="EMPHASIS">vintage</i></span> software
may generate files with <var class="LITERAL">#</var>
characters in the <var class="LITERAL">J</var> line of the
control file. The replacement of this character by underscore
(<var class="LITERAL">_</var>) may cause other applications
which use the control file information to stop working. The
<var class="LITERAL">:safe_chars</var> option allows the user
to specify an additional set of safe characters in the <tt
class="FILENAME">lpd.conf</tt> configuration file(s).</p>
<p>For example, <var class="LITERAL">:safe_chars=#"</var>
would allow the <var class="LITERAL">#</var> and <var class=
"LITERAL">"</var> characters to appear in the control
file.</p>
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