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Next: <a href="Output-Conversion-for-Matrices.html#Output-Conversion-for-Matrices" accesskey="n" rel="next">Output Conversion for Matrices</a>, Previous: <a href="Line_002dOriented-Input.html#Line_002dOriented-Input" accesskey="p" rel="prev">Line-Oriented Input</a>, Up: <a href="C_002dStyle-I_002fO-Functions.html#C_002dStyle-I_002fO-Functions" accesskey="u" rel="up">C-Style I/O Functions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<a name="Formatted-Output-1"></a>
<h4 class="subsection">14.2.4 Formatted Output</h4>
<p>This section describes how to call <code>printf</code> and related functions.
</p>
<p>The following functions are available for formatted output. They are
modeled after the C language functions of the same name, but they
interpret the format template differently in order to improve the
performance of printing vector and matrix values.
</p>
<p>Implementation Note: For compatibility with <small>MATLAB</small>, escape sequences in
the template string (e.g., <code>"\n"</code> => newline) are
expanded even when the template string is defined with single quotes.
</p>
<a name="XREFprintf"></a><dl>
<dt><a name="index-printf"></a><em></em> <strong>printf</strong> <em>(<var>template</var>, …)</em></dt>
<dd><p>Print optional arguments under the control of the template string
<var>template</var> to the stream <code>stdout</code> and return the number of
characters printed.
</p>
<p>See the Formatted Output section of the GNU Octave manual for a
complete description of the syntax of the template string.
</p>
<p>Implementation Note: For compatibility with <small>MATLAB</small>, escape sequences in
the template string (e.g., <code>"\n"</code> => newline) are
expanded even when the template string is defined with single quotes.
</p>
<p><strong>See also:</strong> <a href="#XREFfprintf">fprintf</a>, <a href="#XREFsprintf">sprintf</a>, <a href="Formatted-Input.html#XREFscanf">scanf</a>.
</p></dd></dl>
<a name="XREFfprintf"></a><dl>
<dt><a name="index-fprintf"></a><em></em> <strong>fprintf</strong> <em>(<var>fid</var>, <var>template</var>, …)</em></dt>
<dt><a name="index-fprintf-1"></a><em></em> <strong>fprintf</strong> <em>(<var>template</var>, …)</em></dt>
<dt><a name="index-fprintf-2"></a><em><var>numbytes</var> =</em> <strong>fprintf</strong> <em>(…)</em></dt>
<dd><p>This function is equivalent to <code>printf</code>, except that the output is
written to the file descriptor <var>fid</var> instead of <code>stdout</code>.
</p>
<p>If <var>fid</var> is omitted, the output is written to <code>stdout</code> making the
function exactly equivalent to <code>printf</code>.
</p>
<p>The optional output returns the number of bytes written to the file.
</p>
<p>Implementation Note: For compatibility with <small>MATLAB</small>, escape sequences in
the template string (e.g., <code>"\n"</code> => newline) are
expanded even when the template string is defined with single quotes.
</p>
<p><strong>See also:</strong> <a href="Simple-Output.html#XREFfputs">fputs</a>, <a href="Simple-File-I_002fO.html#XREFfdisp">fdisp</a>, <a href="Binary-I_002fO.html#XREFfwrite">fwrite</a>, <a href="Formatted-Input.html#XREFfscanf">fscanf</a>, <a href="#XREFprintf">printf</a>, <a href="#XREFsprintf">sprintf</a>, <a href="Opening-and-Closing-Files.html#XREFfopen">fopen</a>.
</p></dd></dl>
<a name="XREFsprintf"></a><dl>
<dt><a name="index-sprintf"></a><em></em> <strong>sprintf</strong> <em>(<var>template</var>, …)</em></dt>
<dd><p>This is like <code>printf</code>, except that the output is returned as a
string.
</p>
<p>Unlike the C library function, which requires you to provide a suitably
sized string as an argument, Octave’s <code>sprintf</code> function returns the
string, automatically sized to hold all of the items converted.
</p>
<p>Implementation Note: For compatibility with <small>MATLAB</small>, escape sequences in
the template string (e.g., <code>"\n"</code> => newline) are
expanded even when the template string is defined with single quotes.
</p>
<p><strong>See also:</strong> <a href="#XREFprintf">printf</a>, <a href="#XREFfprintf">fprintf</a>, <a href="Formatted-Input.html#XREFsscanf">sscanf</a>.
</p></dd></dl>
<p>The <code>printf</code> function can be used to print any number of arguments.
The template string argument you supply in a call provides
information not only about the number of additional arguments, but also
about their types and what style should be used for printing them.
</p>
<p>Ordinary characters in the template string are simply written to the
output stream as-is, while <em>conversion specifications</em> introduced by
a ‘<samp>%</samp>’ character in the template cause subsequent arguments to be
formatted and written to the output stream. For example,
<a name="index-conversion-specifications-_0028printf_0029"></a>
</p>
<div class="example">
<pre class="example">pct = 37;
filename = "foo.txt";
printf ("Processed %d%% of '%s'.\nPlease be patient.\n",
pct, filename);
</pre></div>
<p>produces output like
</p>
<div class="example">
<pre class="example">Processed 37% of 'foo.txt'.
Please be patient.
</pre></div>
<p>This example shows the use of the ‘<samp>%d</samp>’ conversion to specify that a
scalar argument should be printed in decimal notation, the ‘<samp>%s</samp>’
conversion to specify printing of a string argument, and the ‘<samp>%%</samp>’
conversion to print a literal ‘<samp>%</samp>’ character.
</p>
<p>There are also conversions for printing an integer argument as an
unsigned value in octal, decimal, or hexadecimal radix (‘<samp>%o</samp>’,
‘<samp>%u</samp>’, or ‘<samp>%x</samp>’, respectively); or as a character value
(‘<samp>%c</samp>’).
</p>
<p>Floating-point numbers can be printed in normal, fixed-point notation
using the ‘<samp>%f</samp>’ conversion or in exponential notation using the
‘<samp>%e</samp>’ conversion. The ‘<samp>%g</samp>’ conversion uses either ‘<samp>%e</samp>’
or ‘<samp>%f</samp>’ format, depending on what is more appropriate for the
magnitude of the particular number.
</p>
<p>You can control formatting more precisely by writing <em>modifiers</em>
between the ‘<samp>%</samp>’ and the character that indicates which conversion
to apply. These slightly alter the ordinary behavior of the conversion.
For example, most conversion specifications permit you to specify a
minimum field width and a flag indicating whether you want the result
left- or right-justified within the field.
</p>
<p>The specific flags and modifiers that are permitted and their
interpretation vary depending on the particular conversion. They’re all
described in more detail in the following sections.
</p>
<hr>
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<p>
Next: <a href="Output-Conversion-for-Matrices.html#Output-Conversion-for-Matrices" accesskey="n" rel="next">Output Conversion for Matrices</a>, Previous: <a href="Line_002dOriented-Input.html#Line_002dOriented-Input" accesskey="p" rel="prev">Line-Oriented Input</a>, Up: <a href="C_002dStyle-I_002fO-Functions.html#C_002dStyle-I_002fO-Functions" accesskey="u" rel="up">C-Style I/O Functions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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