1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<!-- Copyright (C) 1988-2021 Free Software Foundation, Inc. 4 5Permission is granted to copy, distribute and/or modify this document 6under the terms of the GNU Free Documentation License, Version 1.3 or 7any later version published by the Free Software Foundation; with the 8Invariant Sections being "Free Software" and "Free Software Needs 9Free Documentation", with the Front-Cover Texts being "A GNU Manual," 10and with the Back-Cover Texts as in (a) below. 11 12(a) The FSF's Back-Cover Text is: "You are free to copy and modify 13this GNU Manual. 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This is done with the 77<code>define</code> command. User commands may accept an unlimited number of arguments 78separated by whitespace. Arguments are accessed within the user command 79via <code>$arg0…$argN</code>. A trivial example: 80</p> 81<div class="smallexample"> 82<pre class="smallexample">define adder 83 print $arg0 + $arg1 + $arg2 84end 85</pre></div> 86 87<p>To execute the command use: 88</p> 89<div class="smallexample"> 90<pre class="smallexample">adder 1 2 3 91</pre></div> 92 93<p>This defines the command <code>adder</code>, which prints the sum of 94its three arguments. Note the arguments are text substitutions, so they may 95reference variables, use complex expressions, or even perform inferior 96functions calls. 97</p> 98<a name="index-argument-count-in-user_002ddefined-commands"></a> 99<a name="index-how-many-arguments-_0028user_002ddefined-commands_0029"></a> 100<p>In addition, <code>$argc</code> may be used to find out how many arguments have 101been passed. 102</p> 103<div class="smallexample"> 104<pre class="smallexample">define adder 105 if $argc == 2 106 print $arg0 + $arg1 107 end 108 if $argc == 3 109 print $arg0 + $arg1 + $arg2 110 end 111end 112</pre></div> 113 114<p>Combining with the <code>eval</code> command (see <a href="Output.html#eval">eval</a>) makes it easier 115to process a variable number of arguments: 116</p> 117<div class="smallexample"> 118<pre class="smallexample">define adder 119 set $i = 0 120 set $sum = 0 121 while $i < $argc 122 eval "set $sum = $sum + $arg%d", $i 123 set $i = $i + 1 124 end 125 print $sum 126end 127</pre></div> 128 129<dl compact="compact"> 130<dd> 131<a name="index-define"></a> 132</dd> 133<dt><code>define <var>commandname</var></code></dt> 134<dd><p>Define a command named <var>commandname</var>. If there is already a command 135by that name, you are asked to confirm that you want to redefine it. 136The argument <var>commandname</var> may be a bare command name consisting of letters, 137numbers, dashes, dots, and underscores. It may also start with any 138predefined or user-defined prefix command. 139For example, ‘<samp>define target my-target</samp>’ creates 140a user-defined ‘<samp>target my-target</samp>’ command. 141</p> 142<p>The definition of the command is made up of other <small>GDB</small> command lines, 143which are given following the <code>define</code> command. The end of these 144commands is marked by a line containing <code>end</code>. 145</p> 146<a name="index-document"></a> 147<a name="index-end-_0028user_002ddefined-commands_0029"></a> 148</dd> 149<dt><code>document <var>commandname</var></code></dt> 150<dd><p>Document the user-defined command <var>commandname</var>, so that it can be 151accessed by <code>help</code>. The command <var>commandname</var> must already be 152defined. This command reads lines of documentation just as <code>define</code> 153reads the lines of the command definition, ending with <code>end</code>. 154After the <code>document</code> command is finished, <code>help</code> on command 155<var>commandname</var> displays the documentation you have written. 156</p> 157<p>You may use the <code>document</code> command again to change the 158documentation of a command. Redefining the command with <code>define</code> 159does not change the documentation. 160</p> 161<a name="index-define_002dprefix"></a> 162</dd> 163<dt><code>define-prefix <var>commandname</var></code></dt> 164<dd><p>Define or mark the command <var>commandname</var> as a user-defined prefix 165command. Once marked, <var>commandname</var> can be used as prefix command 166by the <code>define</code> command. 167Note that <code>define-prefix</code> can be used with a not yet defined 168<var>commandname</var>. In such a case, <var>commandname</var> is defined as 169an empty user-defined command. 170In case you redefine a command that was marked as a user-defined 171prefix command, the subcommands of the redefined command are kept 172(and <small>GDB</small> indicates so to the user). 173</p> 174<p>Example: 175</p><div class="example"> 176<pre class="example">(gdb) define-prefix abc 177(gdb) define-prefix abc def 178(gdb) define abc def 179Type commands for definition of "abc def". 180End with a line saying just "end". 181>echo command initial def\n 182>end 183(gdb) define abc def ghi 184Type commands for definition of "abc def ghi". 185End with a line saying just "end". 186>echo command ghi\n 187>end 188(gdb) define abc def 189Keeping subcommands of prefix command "def". 190Redefine command "def"? (y or n) y 191Type commands for definition of "abc def". 192End with a line saying just "end". 193>echo command def\n 194>end 195(gdb) abc def ghi 196command ghi 197(gdb) abc def 198command def 199(gdb) 200</pre></div> 201 202<a name="index-dont_002drepeat-1"></a> 203<a name="index-don_0027t-repeat-command"></a> 204</dd> 205<dt><code>dont-repeat</code></dt> 206<dd><p>Used inside a user-defined command, this tells <small>GDB</small> that this 207command should not be repeated when the user hits <tt class="key">RET</tt> 208(see <a href="Command-Syntax.html#Command-Syntax">repeat last command</a>). 209</p> 210<a name="index-help-user_002ddefined"></a> 211</dd> 212<dt><code>help user-defined</code></dt> 213<dd><p>List all user-defined commands and all python commands defined in class 214COMMAND_USER. The first line of the documentation or docstring is 215included (if any). 216</p> 217<a name="index-show-user"></a> 218</dd> 219<dt><code>show user</code></dt> 220<dt><code>show user <var>commandname</var></code></dt> 221<dd><p>Display the <small>GDB</small> commands used to define <var>commandname</var> (but 222not its documentation). If no <var>commandname</var> is given, display the 223definitions for all user-defined commands. 224This does not work for user-defined python commands. 225</p> 226<a name="index-infinite-recursion-in-user_002ddefined-commands"></a> 227<a name="index-show-max_002duser_002dcall_002ddepth"></a> 228<a name="index-set-max_002duser_002dcall_002ddepth"></a> 229</dd> 230<dt><code>show max-user-call-depth</code></dt> 231<dt><code>set max-user-call-depth</code></dt> 232<dd><p>The value of <code>max-user-call-depth</code> controls how many recursion 233levels are allowed in user-defined commands before <small>GDB</small> suspects an 234infinite recursion and aborts the command. 235This does not apply to user-defined python commands. 236</p></dd> 237</dl> 238 239<p>In addition to the above commands, user-defined commands frequently 240use control flow commands, described in <a href="Command-Files.html#Command-Files">Command Files</a>. 241</p> 242<p>When user-defined commands are executed, the 243commands of the definition are not printed. An error in any command 244stops execution of the user-defined command. 245</p> 246<p>If used interactively, commands that would ask for confirmation proceed 247without asking when used inside a user-defined command. Many <small>GDB</small> 248commands that normally print messages to say what they are doing omit the 249messages when used in a user-defined command. 250</p> 251<hr> 252<div class="header"> 253<p> 254Next: <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> 255</div> 256 257 258 259</body> 260</html> 261