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<h3 class="section">2.6 Files</h3>
<p><a name="index-files-9"></a>Files can only be created using the built-in function <code>open</code>. Files
are either readable or writeable. If a file is writeable, text written
to the file may optionally be appended to any existing text.
<p><a name="index-read-10"></a><a name="index-write-11"></a><a name="index-open-12"></a><a name="index-close-13"></a>
<pre class="verbatim">"a" "r" ! open = f1;
"b" "w" ! open = f2;
"c" "a" ! open = f3;
# Read one character
f1 ! read | stdout temp ! write;
# Write a string
f2 "Aaar" ! write;
# Append a string
f3 "Ouu" ! write;
f1!close;f2!close;f3!close;
</pre>
<p>To read an entire file, one must use a loop
construct. See <a href="Loops.html#Loops">Loops</a>. When there are no more characters left, the
<code>read</code> function returns an empty string. Using equality testing,
reading a complete file is thus possible. See <a href="Conditionals.html#Conditionals">Conditionals</a>.
<pre class="verbatim">filename "r" ! open = f;
{f ! read = c; stdout c ! write; c "" ! equal ! not = return;} ! loop;
</pre>
<p>At this point, it may not be obvious why this works. This will be
explained in the next sections.
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