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<h2>15. Import/Export Commands
<a name="15. Import/Export Commands"></a>
</h2>
<p style="margin-top: 1em"><font color="#000000">Commands
that import or export data between <b>pic</b> and its
environment are described here.</font></p>
<h3>15.1. File and Table Insertion
<a name="15.1. File and Table Insertion"></a>
</h3>
<p style="margin-top: 1em"><font color="#000000">The
statement</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><tt>copy</tt>
<i>filename</i></font></p>
<p style="margin-top: 1em"><font color="#000000">inserts
the contents of <i>filename</i> in the <b>pic</b> input
stream. Any <b>.PS</b>/<b>.PE</b> pair in the file is
ignored. You can use this to include pre-generated
images.</font></p>
<p style="margin-top: 1em"><font color="#000000">A variant
of this statement replicates the <b>copy thru</b> feature of
<i>grap</i>(1). The call</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><tt>copy</tt>
<i>filename</i> <tt>thru</tt> <i>macro</i></font></p>
<p style="margin-top: 1em"><font color="#000000">calls
<i>macro</i> (which may be either a name or replacement
text) on the arguments obtained by breaking each line of the
file into blank-separated fields. The macro may have up to
9 arguments. The replacement text may be delimited by
braces or by a pair of instances of any character not
appearing in the rest of the text.</font></p>
<p style="margin-top: 1em"><font color="#000000">If you
write</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><tt>copy
thru</tt> <i>macro</i></font></p>
<p style="margin-top: 1em"><font color="#000000">omitting
the filename, lines to be parsed are taken from the input
source up to the next <b>.PE</b>.</font></p>
<p style="margin-top: 1em"><font color="#000000">In either
of the last two <b>copy</b> commands, GNU <b>gpic</b>
permits a trailing ‘<b>until</b> <i>word</i>’
clause to be added which terminates the copy when the first
word matches the argument (the default behavior is therefore
equivalent to <b>until .PE</b>).</font></p>
<p style="margin-top: 1em"><font color="#000000">Accordingly,
the command</font></p>
<pre style="margin-left:20%; margin-top: 1em">.PS
copy thru % circle at ($1,$2) % until "END"
1 2
3 4
5 6
END
box
.PE</pre>
<p style="margin-top: 1em"><font color="#000000">is
equivalent to</font></p>
<pre style="margin-left:20%; margin-top: 1em">.PS
circle at (1,2)
circle at (3,4)
circle at (5,6)
box
.PE</pre>
<h3>15.2. Debug Messages
<a name="15.2. Debug Messages"></a>
</h3>
<p style="margin-top: 1em"><font color="#000000">The
command <b>print</b> accepts any number of arguments,
concatenates their output forms, and writes the result to
standard error. Each argument must be an expression, a
position, or a text string.</font></p>
<h3>15.3. Escape to Post-Processor
<a name="15.3. Escape to Post-Processor"></a>
</h3>
<p style="margin-top: 1em"><font color="#000000">If you
write</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><b>command</b>
<i>arg</i>...</font></p>
<p style="margin-top: 1em"><font color="#000000"><b>pic</b>
concatenates the arguments and pass them through as a line
to troff or TeX. Each <i>arg</i> must be an expression, a
position, or text. This has a similar effect to a line
beginning with <b>.</b> or <b>\</b>, but allows the values
of variables to be passed through.</font></p>
<p style="margin-top: 1em"><font color="#000000">For
example,</font></p>
<pre style="margin-left:10%; margin-top: 1em">.PS
x = 14
command ".ds string x is " x "."
.PE
\*[string]</pre>
<p style="margin-top: 1em"><font color="#000000">prints</font></p>
<pre style="margin-left:10%; margin-top: 1em">x is 14.</pre>
<h3>15.4. Executing Shell Commands
<a name="15.4. Executing Shell Commands"></a>
</h3>
<p style="margin-top: 1em"><font color="#000000">The
command</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><tt>sh
{</tt> <i>anything...</i> <tt>}</tt></font></p>
<p style="margin-top: 1em"><font color="#000000">macro-expands
the text in braces, then executes it as a shell command.
This could be used to generate images or data tables for
later inclusion. The delimiters shown as {} here may also be
two copies of any one character not present in the shell
command text. In either case, the body may contain balanced
{} pairs. Strings in the body may contain balanced or
unbalanced braces in any case.</font></p>
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