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127 lines
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<title>Aliases - Debugging with GDB</title>
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<link rel="up" href="Extending-GDB.html#Extending-GDB" title="Extending GDB">
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<link rel="prev" href="Multiple-Extension-Languages.html#Multiple-Extension-Languages" title="Multiple Extension Languages">
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<div class="node">
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<a name="Aliases"></a>
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<p>
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Previous: <a rel="previous" accesskey="p" href="Multiple-Extension-Languages.html#Multiple-Extension-Languages">Multiple Extension Languages</a>,
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Up: <a rel="up" accesskey="u" href="Extending-GDB.html#Extending-GDB">Extending GDB</a>
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<hr>
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</div>
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<h3 class="section">23.6 Creating new spellings of existing commands</h3>
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<p><a name="index-aliases-for-commands-2890"></a>
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It is often useful to define alternate spellings of existing commands.
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For example, if a new <span class="sc">gdb</span> 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><span class="sc">gdb</span> itself uses aliases. For example ‘<samp><span class="samp">s</span></samp>’ is an alias
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of the ‘<samp><span class="samp">step</span></samp>’ command even though it is otherwise an ambiguous
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abbreviation of other commands like ‘<samp><span class="samp">set</span></samp>’ and ‘<samp><span class="samp">show</span></samp>’.
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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, <span class="sc">gdb</span> provides the
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‘<samp><span class="samp">tty</span></samp>’ alias of the ‘<samp><span class="samp">set inferior-tty</span></samp>’ command.
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<p>You can define a new alias with the ‘<samp><span class="samp">alias</span></samp>’ command.
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<a name="index-alias-2891"></a>
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<dl><dt><code>alias [-a] [--] </code><var>ALIAS</var><code> = </code><var>COMMAND</var><dd>
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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><var>COMMAND</var> specifies the name of an existing command
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that is being aliased.
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<p>The ‘<samp><span class="samp">-a</span></samp>’ option specifies that the new alias is an abbreviation
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of the command. Abbreviations are not shown in command
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lists displayed by the ‘<samp><span class="samp">help</span></samp>’ command.
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<p>The ‘<samp><span class="samp">--</span></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>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><span class="samp">disas</span></samp>’, the current
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shortest unambiguous abbreviation of the ‘<samp><span class="samp">disassemble</span></samp>’ command
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and you wanted an even shorter version named ‘<samp><span class="samp">di</span></samp>’.
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The following will accomplish this.
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<pre class="smallexample"> (gdb) alias -a di = disas
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</pre>
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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><span class="samp">document</span></samp>’ command.
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An alias automatically picks up the documentation of the existing command.
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<p>Here is an example where we make ‘<samp><span class="samp">elms</span></samp>’ an abbreviation of
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‘<samp><span class="samp">elements</span></samp>’ in the ‘<samp><span class="samp">set print elements</span></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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<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>
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<p>Note that if you are defining an alias of a ‘<samp><span class="samp">set</span></samp>’ command,
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and you want to have an alias for the corresponding ‘<samp><span class="samp">show</span></samp>’
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command, then you need to define the latter separately.
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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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<pre class="smallexample"> (gdb) alias -a set pr elms = set p ele
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</pre>
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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><span class="samp">spe</span></samp>’ of the command ‘<samp><span class="samp">set print elements</span></samp>’.
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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>
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</body></html>
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