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<h4 class="subsection" id="Formatted-Output-1"><span>14.2.4 Formatted Output<a class="copiable-link" href="#Formatted-Output-1"> ¶</a></span></h4>
<p>This section describes how to call <code class="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 class="sc">MATLAB</small>, escape sequences in
the template string (e.g., <code class="code">"\n"</code> => newline) are
expanded even when the template string is defined with single quotes.
</p>
<a class="anchor" id="XREFprintf"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-printf"><span><strong class="def-name">printf</strong> <code class="def-code-arguments">(<var class="var">template</var>, …)</code><a class="copiable-link" href="#index-printf"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-printf-1"><span><code class="def-type"><var class="var">numbytes</var> =</code> <strong class="def-name">printf</strong> <code class="def-code-arguments">(…)</code><a class="copiable-link" href="#index-printf-1"> ¶</a></span></dt>
<dd><p>Print optional arguments under the control of the template string
<var class="var">template</var> to the stream <code class="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>The optional output <var class="var">numbytes</var> returns the number of bytes printed.
</p>
<p>Implementation Note: For compatibility with <small class="sc">MATLAB</small>, escape sequences in
the template string (e.g., <code class="code">"\n"</code> => newline) are
expanded even when the template string is defined with single quotes.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFfprintf">fprintf</a>, <a class="ref" href="#XREFsprintf">sprintf</a>, <a class="ref" href="Formatted-Input.html#XREFscanf">scanf</a>.
</p></dd></dl>
<a class="anchor" id="XREFfprintf"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-fprintf"><span><strong class="def-name">fprintf</strong> <code class="def-code-arguments">(<var class="var">fid</var>, <var class="var">template</var>, …)</code><a class="copiable-link" href="#index-fprintf"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-fprintf-1"><span><strong class="def-name">fprintf</strong> <code class="def-code-arguments">(<var class="var">template</var>, …)</code><a class="copiable-link" href="#index-fprintf-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-fprintf-2"><span><code class="def-type"><var class="var">numbytes</var> =</code> <strong class="def-name">fprintf</strong> <code class="def-code-arguments">(…)</code><a class="copiable-link" href="#index-fprintf-2"> ¶</a></span></dt>
<dd><p>This function is equivalent to <code class="code">printf</code>, except that the output is
written to the file descriptor <var class="var">fid</var> instead of <code class="code">stdout</code>.
</p>
<p>If <var class="var">fid</var> is omitted, the output is written to <code class="code">stdout</code> making the
function exactly equivalent to <code class="code">printf</code>.
</p>
<p>The optional output <var class="var">numbytes</var> returns the number of bytes written to the
file.
</p>
<p>Implementation Note: For compatibility with <small class="sc">MATLAB</small>, escape sequences in
the template string (e.g., <code class="code">"\n"</code> => newline) are
expanded even when the template string is defined with single quotes.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="Simple-Output.html#XREFfputs">fputs</a>, <a class="ref" href="Simple-File-I_002fO.html#XREFfdisp">fdisp</a>, <a class="ref" href="Binary-I_002fO.html#XREFfwrite">fwrite</a>, <a class="ref" href="Formatted-Input.html#XREFfscanf">fscanf</a>, <a class="ref" href="#XREFprintf">printf</a>, <a class="ref" href="#XREFsprintf">sprintf</a>, <a class="ref" href="Opening-and-Closing-Files.html#XREFfopen">fopen</a>.
</p></dd></dl>
<a class="anchor" id="XREFsprintf"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-sprintf"><span><code class="def-type"><var class="var">str</var> =</code> <strong class="def-name">sprintf</strong> <code class="def-code-arguments">(<var class="var">template</var>, …)</code><a class="copiable-link" href="#index-sprintf"> ¶</a></span></dt>
<dd><p>This is like <code class="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 class="code">sprintf</code> function returns the
string, automatically sized to hold all of the items converted.
</p>
<p>Implementation Note: For compatibility with <small class="sc">MATLAB</small>, escape sequences in
the template string (e.g., <code class="code">"\n"</code> => newline) are
expanded even when the template string is defined with single quotes.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFprintf">printf</a>, <a class="ref" href="#XREFfprintf">fprintf</a>, <a class="ref" href="Formatted-Input.html#XREFsscanf">sscanf</a>.
</p></dd></dl>
<p>The <code class="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 class="dfn">conversion specifications</em> introduced by
a ‘<samp class="samp">%</samp>’ character in the template cause subsequent arguments to be
formatted and written to the output stream. For example,
<a class="index-entry-id" id="index-conversion-specifications-_0028printf_0029"></a>
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">pct = 37;
filename = "foo.txt";
printf ("Processed %d%% of '%s'.\nPlease be patient.\n",
pct, filename);
</pre></div></div>
<p>produces output like
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">Processed 37% of 'foo.txt'.
Please be patient.
</pre></div></div>
<p>This example shows the use of the ‘<samp class="samp">%d</samp>’ conversion to specify that a
scalar argument should be printed in decimal notation, the ‘<samp class="samp">%s</samp>’
conversion to specify printing of a string argument, and the ‘<samp class="samp">%%</samp>’
conversion to print a literal ‘<samp class="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 class="samp">%o</samp>’,
‘<samp class="samp">%u</samp>’, or ‘<samp class="samp">%x</samp>’, respectively); or as a character value
(‘<samp class="samp">%c</samp>’).
</p>
<p>Floating-point numbers can be printed in normal, fixed-point notation
using the ‘<samp class="samp">%f</samp>’ conversion or in exponential notation using the
‘<samp class="samp">%e</samp>’ conversion. The ‘<samp class="samp">%g</samp>’ conversion uses either ‘<samp class="samp">%e</samp>’
or ‘<samp class="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 class="dfn">modifiers</em>
between the ‘<samp class="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>
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