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<title>Debugging with GDB: Aliases</title>
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<a name="Aliases"></a>
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<div class="header">
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<p>
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Previous: <a href="Multiple-Extension-Languages.html#Multiple-Extension-Languages" accesskey="p" rel="previous">Multiple Extension Languages</a>, Up: <a href="Extending-GDB.html#Extending-GDB" accesskey="u" rel="up">Extending GDB</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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<hr>
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<a name="Creating-New-Spellings-of-Existing-Commands"></a>
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<h3 class="section">23.6 Creating New Spellings of Existing Commands</h3>
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<a name="index-aliases-for-commands"></a>
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<p>It is often useful to define alternate spellings of existing commands.
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For example, if a new <small>GDB</small> command defined in Python has
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a long name to type, it is handy to have an abbreviated version of it
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that involves less typing.
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</p>
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<p><small>GDB</small> itself uses aliases. For example ‘<samp>s</samp>’ is an alias
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of the ‘<samp>step</samp>’ command even though it is otherwise an ambiguous
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abbreviation of other commands like ‘<samp>set</samp>’ and ‘<samp>show</samp>’.
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</p>
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<p>Aliases are also used to provide shortened or more common versions
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of multi-word commands. For example, <small>GDB</small> provides the
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‘<samp>tty</samp>’ alias of the ‘<samp>set inferior-tty</samp>’ command.
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</p>
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<p>You can define a new alias with the ‘<samp>alias</samp>’ command.
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</p>
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<dl compact="compact">
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<dd>
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<a name="index-alias"></a>
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</dd>
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<dt><code>alias [-a] [--] <var>ALIAS</var> = <var>COMMAND</var> [DEFAULT-ARGS...]</code></dt>
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</dl>
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<p><var>ALIAS</var> specifies the name of the new alias.
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Each word of <var>ALIAS</var> must consist of letters, numbers, dashes and
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underscores.
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</p>
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<p><var>COMMAND</var> specifies the name of an existing command
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that is being aliased.
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</p>
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<p><var>COMMAND</var> can also be the name of an existing alias. In this case,
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<var>COMMAND</var> cannot be an alias that has default arguments.
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</p>
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<p>The ‘<samp>-a</samp>’ option specifies that the new alias is an abbreviation
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of the command. Abbreviations are not used in command completion.
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</p>
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<p>The ‘<samp>--</samp>’ option specifies the end of options,
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and is useful when <var>ALIAS</var> begins with a dash.
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</p>
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<p>You can specify <var>default-args</var> for your alias.
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These <var>default-args</var> will be automatically added before the alias
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arguments typed explicitly on the command line.
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</p>
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<p>For example, the below defines an alias <code>btfullall</code> that shows all local
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variables and all frame arguments:
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</p><div class="smallexample">
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<pre class="smallexample">(gdb) alias btfullall = backtrace -full -frame-arguments all
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</pre></div>
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<p>For more information about <var>default-args</var>, see <a href="Command-aliases-default-args.html#Command-aliases-default-args">Automatically prepend default arguments to user-defined aliases</a>.
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</p>
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<p>Here is a simple example showing how to make an abbreviation
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of a command so that there is less to type.
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Suppose you were tired of typing ‘<samp>disas</samp>’, the current
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shortest unambiguous abbreviation of the ‘<samp>disassemble</samp>’ command
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and you wanted an even shorter version named ‘<samp>di</samp>’.
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The following will accomplish this.
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</p>
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<div class="smallexample">
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<pre class="smallexample">(gdb) alias -a di = disas
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</pre></div>
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<p>Note that aliases are different from user-defined commands.
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With a user-defined command, you also need to write documentation
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for it with the ‘<samp>document</samp>’ command.
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An alias automatically picks up the documentation of the existing command.
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</p>
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<p>Here is an example where we make ‘<samp>elms</samp>’ an abbreviation of
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‘<samp>elements</samp>’ in the ‘<samp>set print elements</samp>’ command.
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This is to show that you can make an abbreviation of any part
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of a command.
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</p>
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<div class="smallexample">
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<pre class="smallexample">(gdb) alias -a set print elms = set print elements
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(gdb) alias -a show print elms = show print elements
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(gdb) set p elms 20
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(gdb) show p elms
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Limit on string chars or array elements to print is 200.
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</pre></div>
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<p>Note that if you are defining an alias of a ‘<samp>set</samp>’ command,
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and you want to have an alias for the corresponding ‘<samp>show</samp>’
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command, then you need to define the latter separately.
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</p>
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<p>Unambiguously abbreviated commands are allowed in <var>COMMAND</var> and
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<var>ALIAS</var>, just as they are normally.
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</p>
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<div class="smallexample">
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<pre class="smallexample">(gdb) alias -a set pr elms = set p ele
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</pre></div>
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<p>Finally, here is an example showing the creation of a one word
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alias for a more complex command.
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This creates alias ‘<samp>spe</samp>’ of the command ‘<samp>set print elements</samp>’.
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</p>
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<div class="smallexample">
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<pre class="smallexample">(gdb) alias spe = set print elements
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(gdb) spe 20
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</pre></div>
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<div class="header">
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<p>
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Previous: <a href="Multiple-Extension-Languages.html#Multiple-Extension-Languages" accesskey="p" rel="previous">Multiple Extension Languages</a>, Up: <a href="Extending-GDB.html#Extending-GDB" accesskey="u" rel="up">Extending GDB</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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