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| <title>Debugging with GDB: Define</title> |
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| <a name="Define"></a> |
| <div class="header"> |
| <p> |
| Next: <a href="Hooks.html#Hooks" accesskey="n" rel="next">Hooks</a>, Up: <a href="Sequences.html#Sequences" accesskey="u" rel="up">Sequences</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> |
| <a name="User_002ddefined-Commands"></a> |
| <h4 class="subsection">23.1.1 User-defined Commands</h4> |
| |
| <a name="index-user_002ddefined-command"></a> |
| <a name="index-arguments_002c-to-user_002ddefined-commands"></a> |
| <p>A <em>user-defined command</em> is a sequence of <small>GDB</small> commands to |
| which you assign a new name as a command. This is done with the |
| <code>define</code> command. User commands may accept up to 10 arguments |
| separated by whitespace. Arguments are accessed within the user command |
| via <code>$arg0…$arg9</code>. A trivial example: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">define adder |
| print $arg0 + $arg1 + $arg2 |
| end |
| </pre></div> |
| |
| <p>To execute the command use: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">adder 1 2 3 |
| </pre></div> |
| |
| <p>This defines the command <code>adder</code>, which prints the sum of |
| its three arguments. Note the arguments are text substitutions, so they may |
| reference variables, use complex expressions, or even perform inferior |
| functions calls. |
| </p> |
| <a name="index-argument-count-in-user_002ddefined-commands"></a> |
| <a name="index-how-many-arguments-_0028user_002ddefined-commands_0029"></a> |
| <p>In addition, <code>$argc</code> may be used to find out how many arguments have |
| been passed. This expands to a number in the range 0…10. |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">define adder |
| if $argc == 2 |
| print $arg0 + $arg1 |
| end |
| if $argc == 3 |
| print $arg0 + $arg1 + $arg2 |
| end |
| end |
| </pre></div> |
| |
| <dl compact="compact"> |
| <dd> |
| <a name="index-define"></a> |
| </dd> |
| <dt><code>define <var>commandname</var></code></dt> |
| <dd><p>Define a command named <var>commandname</var>. If there is already a command |
| by that name, you are asked to confirm that you want to redefine it. |
| The argument <var>commandname</var> may be a bare command name consisting of letters, |
| numbers, dashes, and underscores. It may also start with any predefined |
| prefix command. For example, ‘<samp>define target my-target</samp>’ creates |
| a user-defined ‘<samp>target my-target</samp>’ command. |
| </p> |
| <p>The definition of the command is made up of other <small>GDB</small> command lines, |
| which are given following the <code>define</code> command. The end of these |
| commands is marked by a line containing <code>end</code>. |
| </p> |
| <a name="index-document"></a> |
| <a name="index-end-_0028user_002ddefined-commands_0029"></a> |
| </dd> |
| <dt><code>document <var>commandname</var></code></dt> |
| <dd><p>Document the user-defined command <var>commandname</var>, so that it can be |
| accessed by <code>help</code>. The command <var>commandname</var> must already be |
| defined. This command reads lines of documentation just as <code>define</code> |
| reads the lines of the command definition, ending with <code>end</code>. |
| After the <code>document</code> command is finished, <code>help</code> on command |
| <var>commandname</var> displays the documentation you have written. |
| </p> |
| <p>You may use the <code>document</code> command again to change the |
| documentation of a command. Redefining the command with <code>define</code> |
| does not change the documentation. |
| </p> |
| <a name="index-dont_002drepeat-1"></a> |
| <a name="index-don_0027t-repeat-command"></a> |
| </dd> |
| <dt><code>dont-repeat</code></dt> |
| <dd><p>Used inside a user-defined command, this tells <small>GDB</small> that this |
| command should not be repeated when the user hits <tt class="key">RET</tt> |
| (see <a href="Command-Syntax.html#Command-Syntax">repeat last command</a>). |
| </p> |
| <a name="index-help-user_002ddefined"></a> |
| </dd> |
| <dt><code>help user-defined</code></dt> |
| <dd><p>List all user-defined commands and all python commands defined in class |
| COMAND_USER. The first line of the documentation or docstring is |
| included (if any). |
| </p> |
| <a name="index-show-user"></a> |
| </dd> |
| <dt><code>show user</code></dt> |
| <dt><code>show user <var>commandname</var></code></dt> |
| <dd><p>Display the <small>GDB</small> commands used to define <var>commandname</var> (but |
| not its documentation). If no <var>commandname</var> is given, display the |
| definitions for all user-defined commands. |
| This does not work for user-defined python commands. |
| </p> |
| <a name="index-infinite-recursion-in-user_002ddefined-commands"></a> |
| <a name="index-show-max_002duser_002dcall_002ddepth"></a> |
| <a name="index-set-max_002duser_002dcall_002ddepth"></a> |
| </dd> |
| <dt><code>show max-user-call-depth</code></dt> |
| <dt><code>set max-user-call-depth</code></dt> |
| <dd><p>The value of <code>max-user-call-depth</code> controls how many recursion |
| levels are allowed in user-defined commands before <small>GDB</small> suspects an |
| infinite recursion and aborts the command. |
| This does not apply to user-defined python commands. |
| </p></dd> |
| </dl> |
| |
| <p>In addition to the above commands, user-defined commands frequently |
| use control flow commands, described in <a href="Command-Files.html#Command-Files">Command Files</a>. |
| </p> |
| <p>When user-defined commands are executed, the |
| commands of the definition are not printed. An error in any command |
| stops execution of the user-defined command. |
| </p> |
| <p>If used interactively, commands that would ask for confirmation proceed |
| without asking when used inside a user-defined command. Many <small>GDB</small> |
| commands that normally print messages to say what they are doing omit the |
| messages when used in a user-defined command. |
| </p> |
| <hr> |
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| Next: <a href="Hooks.html#Hooks" accesskey="n" rel="next">Hooks</a>, Up: <a href="Sequences.html#Sequences" accesskey="u" rel="up">Sequences</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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