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<a name="Help"></a>
<div class="header">
<p>
Previous: <a href="Command-aliases-default-args.html#Command-aliases-default-args" accesskey="p" rel="previous">Command aliases default args</a>, Up: <a href="Commands.html#Commands" accesskey="u" rel="up">Commands</a> &nbsp; [<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>
</div>
<hr>
<a name="Getting-Help"></a>
<h3 class="section">3.6 Getting Help</h3>
<a name="index-online-documentation"></a>
<a name="index-help"></a>

<p>You can always ask <small>GDB</small> itself for information on its commands,
using the command <code>help</code>.
</p>
<dl compact="compact">
<dd><a name="index-h-_0028help_0029"></a>
</dd>
<dt><code>help</code></dt>
<dt><code>h</code></dt>
<dd><p>You can use <code>help</code> (abbreviated <code>h</code>) with no arguments to
display a short list of named classes of commands:
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) help
List of classes of commands:

aliases -- User-defined aliases of other commands
breakpoints -- Making program stop at certain points
data -- Examining data
files -- Specifying and examining files
internals -- Maintenance commands
obscure -- Obscure features
running -- Running the program
stack -- Examining the stack
status -- Status inquiries
support -- Support facilities
tracepoints -- Tracing of program execution without
               stopping the program
user-defined -- User-defined commands

Type &quot;help&quot; followed by a class name for a list of
commands in that class.
Type &quot;help&quot; followed by command name for full
documentation.
Command name abbreviations are allowed if unambiguous.
(gdb)
</pre></div>

</dd>
<dt><code>help <var>class</var></code></dt>
<dd><p>Using one of the general help classes as an argument, you can get a
list of the individual commands in that class.  If a command has
aliases, the aliases are given after the command name, separated by
commas.  If an alias has default arguments, the full definition of
the alias is given after the first line.
For example, here is the help display for the class <code>status</code>:
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) help status
Status inquiries.

List of commands:

info, inf, i -- Generic command for showing things
        about the program being debugged
info address, iamain  -- Describe where symbol SYM is stored.
  alias iamain = info address main
info all-registers -- List of all registers and their contents,
        for selected stack frame.
...
show, info set -- Generic command for showing things
        about the debugger

Type &quot;help&quot; followed by command name for full
documentation.
Command name abbreviations are allowed if unambiguous.
(gdb)
</pre></div>

</dd>
<dt><code>help <var>command</var></code></dt>
<dd><p>With a command name as <code>help</code> argument, <small>GDB</small> displays a
short paragraph on how to use that command.  If that command has
one or more aliases, <small>GDB</small> will display a first line with
the command name and all its aliases separated by commas.
This first line will be followed by the full definition of all aliases
having default arguments.
</p>
<a name="index-apropos"></a>
</dd>
<dt><code>apropos [-v] <var>regexp</var></code></dt>
<dd><p>The <code>apropos</code> command searches through all of the <small>GDB</small>
commands, and their documentation, for the regular expression specified in
<var>args</var>.  It prints out all matches found.  The optional flag  &lsquo;<samp>-v</samp>&rsquo;,
which stands for &lsquo;<samp>verbose</samp>&rsquo;, indicates to output the full documentation
of the matching commands and highlight the parts of the documentation
matching <var>regexp</var>.  For example:
</p>
<div class="smallexample">
<pre class="smallexample">apropos alias
</pre></div>

<p>results in:
</p>
<div class="smallexample">
<pre class="smallexample">alias -- Define a new command that is an alias of an existing command
aliases -- User-defined aliases of other commands
</pre></div>

<p>while
</p>
<div class="smallexample">
<pre class="smallexample">apropos -v cut.*thread apply
</pre></div>

<p>results in the below output, where &lsquo;<samp>cut for 'thread apply</samp>&rsquo;
is highlighted if styling is enabled.
</p>
<div class="smallexample">
<pre class="smallexample">taas -- Apply a command to all threads (ignoring errors
and empty output).
Usage: taas COMMAND
shortcut for 'thread apply all -s COMMAND'

tfaas -- Apply a command to all frames of all threads
(ignoring errors and empty output).
Usage: tfaas COMMAND
shortcut for 'thread apply all -s frame apply all -s COMMAND'
</pre></div>

<a name="index-complete"></a>
</dd>
<dt><code>complete <var>args</var></code></dt>
<dd><p>The <code>complete <var>args</var></code> command lists all the possible completions
for the beginning of a command.  Use <var>args</var> to specify the beginning of the
command you want completed.  For example:
</p>
<div class="smallexample">
<pre class="smallexample">complete i
</pre></div>

<p>results in:
</p>
<div class="smallexample">
<pre class="smallexample">if
ignore
info
inspect
</pre></div>

<p>This is intended for use by <small>GNU</small> Emacs.
</p></dd>
</dl>

<p>In addition to <code>help</code>, you can use the <small>GDB</small> commands <code>info</code>
and <code>show</code> to inquire about the state of your program, or the state
of <small>GDB</small> itself.  Each command supports many topics of inquiry; this
manual introduces each of them in the appropriate context.  The listings
under <code>info</code> and under <code>show</code> in the Command, Variable, and
Function Index point to all the sub-commands.  See <a href="Command-and-Variable-Index.html#Command-and-Variable-Index">Command and Variable Index</a>.
</p>
<dl compact="compact">
<dd><a name="index-info"></a>
<a name="index-i-_0028info_0029"></a>
</dd>
<dt><code>info</code></dt>
<dd><p>This command (abbreviated <code>i</code>) is for describing the state of your
program.  For example, you can show the arguments passed to a function
with <code>info args</code>, list the registers currently in use with <code>info
registers</code>, or list the breakpoints you have set with <code>info breakpoints</code>.
You can get a complete list of the <code>info</code> sub-commands with
<code>help&nbsp;info</code><!-- /@w -->.
</p>
<a name="index-set"></a>
</dd>
<dt><code>set</code></dt>
<dd><p>You can assign the result of an expression to an environment variable with
<code>set</code>.  For example, you can set the <small>GDB</small> prompt to a $-sign with
<code>set prompt $</code>.
</p>
<a name="index-show"></a>
</dd>
<dt><code>show</code></dt>
<dd><p>In contrast to <code>info</code>, <code>show</code> is for describing the state of
<small>GDB</small> itself.
You can change most of the things you can <code>show</code>, by using the
related command <code>set</code>; for example, you can control what number
system is used for displays with <code>set radix</code>, or simply inquire
which is currently in use with <code>show radix</code>.
</p>
<a name="index-info-set"></a>
<p>To display all the settable parameters and their current
values, you can use <code>show</code> with no arguments; you may also use
<code>info set</code>.  Both commands produce the same display.
</p></dd>
</dl>

<p>Here are several miscellaneous <code>show</code> subcommands, all of which are
exceptional in lacking corresponding <code>set</code> commands:
</p>
<dl compact="compact">
<dd><a name="index-show-version"></a>
<a name="index-GDB-version-number"></a>
</dd>
<dt><code>show version</code></dt>
<dd><p>Show what version of <small>GDB</small> is running.  You should include this
information in <small>GDB</small> bug-reports.  If multiple versions of
<small>GDB</small> are in use at your site, you may need to determine which
version of <small>GDB</small> you are running; as <small>GDB</small> evolves, new
commands are introduced, and old ones may wither away.  Also, many
system vendors ship variant versions of <small>GDB</small>, and there are
variant versions of <small>GDB</small> in <small>GNU</small>/Linux distributions as well.
The version number is the same as the one announced when you start
<small>GDB</small>.
</p>
<a name="index-show-copying"></a>
<a name="index-info-copying"></a>
<a name="index-display-GDB-copyright"></a>
</dd>
<dt><code>show copying</code></dt>
<dt><code>info copying</code></dt>
<dd><p>Display information about permission for copying <small>GDB</small>.
</p>
<a name="index-show-warranty"></a>
<a name="index-info-warranty"></a>
</dd>
<dt><code>show warranty</code></dt>
<dt><code>info warranty</code></dt>
<dd><p>Display the <small>GNU</small> &ldquo;NO WARRANTY&rdquo; statement, or a warranty,
if your version of <small>GDB</small> comes with one.
</p>
<a name="index-show-configuration"></a>
</dd>
<dt><code>show configuration</code></dt>
<dd><p>Display detailed information about the way <small>GDB</small> was configured
when it was built.  This displays the optional arguments passed to the
<samp>configure</samp> script and also configuration parameters detected
automatically by <code>configure</code>.  When reporting a <small>GDB</small>
bug (see <a href="GDB-Bugs.html#GDB-Bugs">GDB Bugs</a>), it is important to include this information in
your report.
</p>
</dd>
</dl>

<hr>
<div class="header">
<p>
Previous: <a href="Command-aliases-default-args.html#Command-aliases-default-args" accesskey="p" rel="previous">Command aliases default args</a>, Up: <a href="Commands.html#Commands" accesskey="u" rel="up">Commands</a> &nbsp; [<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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