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<a name="Command-Options"></a>
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<p>
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<hr>
<a name="Command-options"></a>
<h3 class="section">3.4 Command options</h3>

<a name="index-command-options"></a>
<p>Some commands accept options starting with a leading dash.  For
example, <code>print -pretty</code>.  Similarly to command names, you can
abbreviate a <small>GDB</small> option to the first few letters of the
option name, if that abbreviation is unambiguous, and you can also use
the <tt class="key">TAB</tt> key to get <small>GDB</small> to fill out the rest of a word
in an option (or to show you the alternatives available, if there is
more than one possibility).
</p>
<a name="index-command-options_002c-raw-input"></a>
<p>Some commands take raw input as argument.  For example, the print
command processes arbitrary expressions in any of the languages
supported by <small>GDB</small>.  With such commands, because raw input may
start with a leading dash that would be confused with an option or any
of its abbreviations, e.g. <code>print -p</code> (short for <code>print
-pretty</code> or printing negative <code>p</code>?), if you specify any command
option, then you must use a double-dash (<code>--</code>) delimiter to
indicate the end of options.
</p>
<a name="index-command-options_002c-boolean"></a>

<p>Some options are described as accepting an argument which can be
either <code>on</code> or <code>off</code>.  These are known as <em>boolean
options</em>.  Similarly to boolean settings commands&mdash;<code>on</code> and
<code>off</code> are the typical values, but any of <code>1</code>, <code>yes</code> and
<code>enable</code> can also be used as &ldquo;true&rdquo; value, and any of <code>0</code>,
<code>no</code> and <code>disable</code> can also be used as &ldquo;false&rdquo; value.  You
can also omit a &ldquo;true&rdquo; value, as it is implied by default.
</p>
<p>For example, these are equivalent:
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) print -object on -pretty off -element unlimited -- *myptr
(gdb) p -o -p 0 -e u -- *myptr
</pre></div>

<p>You can discover the set of options some command accepts by completing
on <code>-</code> after the command name.  For example:
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) print -<span class="key">TAB</span><span class="key">TAB</span>
-address         -max-depth       -raw-values      -union
-array           -null-stop       -repeats         -vtbl
-array-indexes   -object          -static-members
-elements        -pretty          -symbol
</pre></div>

<p>Completion will in some cases guide you with a suggestion of what kind
of argument an option expects.  For example:
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) print -elements <span class="key">TAB</span><span class="key">TAB</span>
NUMBER     unlimited
</pre></div>

<p>Here, the option expects a number (e.g., <code>100</code>), not literal
<code>NUMBER</code>.  Such metasyntactical arguments are always presented in
uppercase.
</p>
<p>(For more on using the <code>print</code> command, see <a href="Data.html#Data">Examining
Data</a>.)
</p>
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