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276 lines
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<html lang="en">
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<head>
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<title>Commands In Python - Debugging with GDB</title>
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<meta name="description" content="Debugging with GDB">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Python-API.html#Python-API" title="Python API">
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<link rel="prev" href="Recordings-In-Python.html#Recordings-In-Python" title="Recordings In Python">
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<link rel="next" href="Parameters-In-Python.html#Parameters-In-Python" title="Parameters In Python">
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being ``Free Software'' and ``Free Software Needs
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and with the Back-Cover Texts as in (a) below.
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<body>
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<div class="node">
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<a name="Commands-In-Python"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Parameters-In-Python.html#Parameters-In-Python">Parameters In Python</a>,
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Previous: <a rel="previous" accesskey="p" href="Recordings-In-Python.html#Recordings-In-Python">Recordings In Python</a>,
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Up: <a rel="up" accesskey="u" href="Python-API.html#Python-API">Python API</a>
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<hr>
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</div>
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<h5 class="subsubsection">23.2.2.20 Commands In Python</h5>
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<p><a name="index-commands-in-python-2138"></a><a name="index-python-commands-2139"></a>You can implement new <span class="sc">gdb</span> CLI commands in Python. A CLI
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command is implemented using an instance of the <code>gdb.Command</code>
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class, most commonly using a subclass.
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<div class="defun">
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— Function: <b>Command.__init__</b> (<var>name, command_class </var><span class="roman">[</span><var>, completer_class </var><span class="roman">[</span><var>, prefix</var><span class="roman">]]</span>)<var><a name="index-Command_002e_005f_005finit_005f_005f-2140"></a></var><br>
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<blockquote><p>The object initializer for <code>Command</code> registers the new command
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with <span class="sc">gdb</span>. This initializer is normally invoked from the
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subclass' own <code>__init__</code> method.
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<p><var>name</var> is the name of the command. If <var>name</var> consists of
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multiple words, then the initial words are looked for as prefix
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commands. In this case, if one of the prefix commands does not exist,
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an exception is raised.
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<p>There is no support for multi-line commands.
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<p><var>command_class</var> should be one of the ‘<samp><span class="samp">COMMAND_</span></samp>’ constants
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defined below. This argument tells <span class="sc">gdb</span> how to categorize the
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new command in the help system.
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<p><var>completer_class</var> is an optional argument. If given, it should be
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one of the ‘<samp><span class="samp">COMPLETE_</span></samp>’ constants defined below. This argument
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tells <span class="sc">gdb</span> how to perform completion for this command. If not
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given, <span class="sc">gdb</span> will attempt to complete using the object's
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<code>complete</code> method (see below); if no such method is found, an
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error will occur when completion is attempted.
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<p><var>prefix</var> is an optional argument. If <code>True</code>, then the new
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command is a prefix command; sub-commands of this command may be
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registered.
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<p>The help text for the new command is taken from the Python
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documentation string for the command's class, if there is one. If no
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documentation string is provided, the default value “This command is
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not documented.” is used.
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</p></blockquote></div>
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<p><a name="index-don_0027t-repeat-Python-command-2141"></a>
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<div class="defun">
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— Function: <b>Command.dont_repeat</b> ()<var><a name="index-Command_002edont_005frepeat-2142"></a></var><br>
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<blockquote><p>By default, a <span class="sc">gdb</span> command is repeated when the user enters a
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blank line at the command prompt. A command can suppress this
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behavior by invoking the <code>dont_repeat</code> method. This is similar
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to the user command <code>dont-repeat</code>, see <a href="Define.html#Define">dont-repeat</a>.
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</p></blockquote></div>
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<div class="defun">
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— Function: <b>Command.invoke</b> (<var>argument, from_tty</var>)<var><a name="index-Command_002einvoke-2143"></a></var><br>
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<blockquote><p>This method is called by <span class="sc">gdb</span> when this command is invoked.
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<p><var>argument</var> is a string. It is the argument to the command, after
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leading and trailing whitespace has been stripped.
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<p><var>from_tty</var> is a boolean argument. When true, this means that the
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command was entered by the user at the terminal; when false it means
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that the command came from elsewhere.
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<p>If this method throws an exception, it is turned into a <span class="sc">gdb</span>
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<code>error</code> call. Otherwise, the return value is ignored.
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<p><a name="index-gdb_002estring_005fto_005fargv-2144"></a>To break <var>argument</var> up into an argv-like string use
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<code>gdb.string_to_argv</code>. This function behaves identically to
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<span class="sc">gdb</span>'s internal argument lexer <code>buildargv</code>.
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It is recommended to use this for consistency.
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Arguments are separated by spaces and may be quoted.
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Example:
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<pre class="smallexample"> print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
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['1', '2 "3', '4 "5', "6 '7"]
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</pre>
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</blockquote></div>
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<p><a name="index-completion-of-Python-commands-2145"></a>
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<div class="defun">
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— Function: <b>Command.complete</b> (<var>text, word</var>)<var><a name="index-Command_002ecomplete-2146"></a></var><br>
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<blockquote><p>This method is called by <span class="sc">gdb</span> when the user attempts
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completion on this command. All forms of completion are handled by
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this method, that is, the <TAB> and <M-?> key bindings
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(see <a href="Completion.html#Completion">Completion</a>), and the <code>complete</code> command (see <a href="Help.html#Help">complete</a>).
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<p>The arguments <var>text</var> and <var>word</var> are both strings; <var>text</var>
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holds the complete command line up to the cursor's location, while
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<var>word</var> holds the last word of the command line; this is computed
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using a word-breaking heuristic.
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<p>The <code>complete</code> method can return several values:
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<ul>
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<li>If the return value is a sequence, the contents of the sequence are
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used as the completions. It is up to <code>complete</code> to ensure that the
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contents actually do complete the word. A zero-length sequence is
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allowed, it means that there were no completions available. Only
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string elements of the sequence are used; other elements in the
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sequence are ignored.
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<li>If the return value is one of the ‘<samp><span class="samp">COMPLETE_</span></samp>’ constants defined
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below, then the corresponding <span class="sc">gdb</span>-internal completion
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function is invoked, and its result is used.
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<li>All other results are treated as though there were no available
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completions.
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</ul>
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</p></blockquote></div>
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<p>When a new command is registered, it must be declared as a member of
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some general class of commands. This is used to classify top-level
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commands in the on-line help system; note that prefix commands are not
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listed under their own category but rather that of their top-level
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command. The available classifications are represented by constants
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defined in the <code>gdb</code> module:
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<a name="index-COMMAND_005fNONE-2147"></a>
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<a name="index-gdb_002eCOMMAND_005fNONE-2148"></a>
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<dl><dt><code>gdb.COMMAND_NONE</code><dd>The command does not belong to any particular class. A command in
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this category will not be displayed in any of the help categories.
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<p><a name="index-COMMAND_005fRUNNING-2149"></a><a name="index-gdb_002eCOMMAND_005fRUNNING-2150"></a><br><dt><code>gdb.COMMAND_RUNNING</code><dd>The command is related to running the inferior. For example,
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<code>start</code>, <code>step</code>, and <code>continue</code> are in this category.
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Type <kbd>help running</kbd> at the <span class="sc">gdb</span> prompt to see a list of
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commands in this category.
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<p><a name="index-COMMAND_005fDATA-2151"></a><a name="index-gdb_002eCOMMAND_005fDATA-2152"></a><br><dt><code>gdb.COMMAND_DATA</code><dd>The command is related to data or variables. For example,
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<code>call</code>, <code>find</code>, and <code>print</code> are in this category. Type
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<kbd>help data</kbd> at the <span class="sc">gdb</span> prompt to see a list of commands
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in this category.
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<p><a name="index-COMMAND_005fSTACK-2153"></a><a name="index-gdb_002eCOMMAND_005fSTACK-2154"></a><br><dt><code>gdb.COMMAND_STACK</code><dd>The command has to do with manipulation of the stack. For example,
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<code>backtrace</code>, <code>frame</code>, and <code>return</code> are in this
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category. Type <kbd>help stack</kbd> at the <span class="sc">gdb</span> prompt to see a
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list of commands in this category.
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<p><a name="index-COMMAND_005fFILES-2155"></a><a name="index-gdb_002eCOMMAND_005fFILES-2156"></a><br><dt><code>gdb.COMMAND_FILES</code><dd>This class is used for file-related commands. For example,
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<code>file</code>, <code>list</code> and <code>section</code> are in this category.
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Type <kbd>help files</kbd> at the <span class="sc">gdb</span> prompt to see a list of
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commands in this category.
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<p><a name="index-COMMAND_005fSUPPORT-2157"></a><a name="index-gdb_002eCOMMAND_005fSUPPORT-2158"></a><br><dt><code>gdb.COMMAND_SUPPORT</code><dd>This should be used for “support facilities”, generally meaning
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things that are useful to the user when interacting with <span class="sc">gdb</span>,
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but not related to the state of the inferior. For example,
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<code>help</code>, <code>make</code>, and <code>shell</code> are in this category. Type
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<kbd>help support</kbd> at the <span class="sc">gdb</span> prompt to see a list of
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commands in this category.
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<p><a name="index-COMMAND_005fSTATUS-2159"></a><a name="index-gdb_002eCOMMAND_005fSTATUS-2160"></a><br><dt><code>gdb.COMMAND_STATUS</code><dd>The command is an ‘<samp><span class="samp">info</span></samp>’-related command, that is, related to the
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state of <span class="sc">gdb</span> itself. For example, <code>info</code>, <code>macro</code>,
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and <code>show</code> are in this category. Type <kbd>help status</kbd> at the
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<span class="sc">gdb</span> prompt to see a list of commands in this category.
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<p><a name="index-COMMAND_005fBREAKPOINTS-2161"></a><a name="index-gdb_002eCOMMAND_005fBREAKPOINTS-2162"></a><br><dt><code>gdb.COMMAND_BREAKPOINTS</code><dd>The command has to do with breakpoints. For example, <code>break</code>,
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<code>clear</code>, and <code>delete</code> are in this category. Type <kbd>help
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breakpoints</kbd> at the <span class="sc">gdb</span> prompt to see a list of commands in
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this category.
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<p><a name="index-COMMAND_005fTRACEPOINTS-2163"></a><a name="index-gdb_002eCOMMAND_005fTRACEPOINTS-2164"></a><br><dt><code>gdb.COMMAND_TRACEPOINTS</code><dd>The command has to do with tracepoints. For example, <code>trace</code>,
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<code>actions</code>, and <code>tfind</code> are in this category. Type
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<kbd>help tracepoints</kbd> at the <span class="sc">gdb</span> prompt to see a list of
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commands in this category.
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<p><a name="index-COMMAND_005fUSER-2165"></a><a name="index-gdb_002eCOMMAND_005fUSER-2166"></a><br><dt><code>gdb.COMMAND_USER</code><dd>The command is a general purpose command for the user, and typically
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does not fit in one of the other categories.
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Type <kbd>help user-defined</kbd> at the <span class="sc">gdb</span> prompt to see
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a list of commands in this category, as well as the list of gdb macros
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(see <a href="Sequences.html#Sequences">Sequences</a>).
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<p><a name="index-COMMAND_005fOBSCURE-2167"></a><a name="index-gdb_002eCOMMAND_005fOBSCURE-2168"></a><br><dt><code>gdb.COMMAND_OBSCURE</code><dd>The command is only used in unusual circumstances, or is not of
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general interest to users. For example, <code>checkpoint</code>,
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<code>fork</code>, and <code>stop</code> are in this category. Type <kbd>help
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obscure</kbd> at the <span class="sc">gdb</span> prompt to see a list of commands in this
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category.
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<p><a name="index-COMMAND_005fMAINTENANCE-2169"></a><a name="index-gdb_002eCOMMAND_005fMAINTENANCE-2170"></a><br><dt><code>gdb.COMMAND_MAINTENANCE</code><dd>The command is only useful to <span class="sc">gdb</span> maintainers. The
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<code>maintenance</code> and <code>flushregs</code> commands are in this category.
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Type <kbd>help internals</kbd> at the <span class="sc">gdb</span> prompt to see a list of
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commands in this category.
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</dl>
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<p>A new command can use a predefined completion function, either by
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specifying it via an argument at initialization, or by returning it
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from the <code>complete</code> method. These predefined completion
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constants are all defined in the <code>gdb</code> module:
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<a name="index-COMPLETE_005fNONE-2171"></a>
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<dl><dt><code>gdb.COMPLETE_NONE</code><a name="index-gdb_002eCOMPLETE_005fNONE-2172"></a><dd>This constant means that no completion should be done.
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<p><a name="index-COMPLETE_005fFILENAME-2173"></a><br><dt><code>gdb.COMPLETE_FILENAME</code><a name="index-gdb_002eCOMPLETE_005fFILENAME-2174"></a><dd>This constant means that filename completion should be performed.
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<p><a name="index-COMPLETE_005fLOCATION-2175"></a><br><dt><code>gdb.COMPLETE_LOCATION</code><a name="index-gdb_002eCOMPLETE_005fLOCATION-2176"></a><dd>This constant means that location completion should be done.
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See <a href="Specify-Location.html#Specify-Location">Specify Location</a>.
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<p><a name="index-COMPLETE_005fCOMMAND-2177"></a><br><dt><code>gdb.COMPLETE_COMMAND</code><a name="index-gdb_002eCOMPLETE_005fCOMMAND-2178"></a><dd>This constant means that completion should examine <span class="sc">gdb</span>
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command names.
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<p><a name="index-COMPLETE_005fSYMBOL-2179"></a><br><dt><code>gdb.COMPLETE_SYMBOL</code><a name="index-gdb_002eCOMPLETE_005fSYMBOL-2180"></a><dd>This constant means that completion should be done using symbol names
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as the source.
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<p><a name="index-COMPLETE_005fEXPRESSION-2181"></a><br><dt><code>gdb.COMPLETE_EXPRESSION</code><a name="index-gdb_002eCOMPLETE_005fEXPRESSION-2182"></a><dd>This constant means that completion should be done on expressions.
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Often this means completing on symbol names, but some language
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parsers also have support for completing on field names.
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</dl>
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<p>The following code snippet shows how a trivial CLI command can be
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implemented in Python:
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<pre class="smallexample"> class HelloWorld (gdb.Command):
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"""Greet the whole world."""
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def __init__ (self):
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super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
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def invoke (self, arg, from_tty):
|
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print "Hello, World!"
|
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|
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|
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HelloWorld ()
|
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</pre>
|
||
|
|
<p>The last line instantiates the class, and is necessary to trigger the
|
||
|
|
registration of the command with <span class="sc">gdb</span>. Depending on how the
|
||
|
|
Python code is read into <span class="sc">gdb</span>, you may need to import the
|
||
|
|
<code>gdb</code> module explicitly.
|
||
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</body></html>
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