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. Buying copies from GNU Press supports the FSF in 14developing GNU and promoting software freedom." --> 15<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> 16<head> 17<title>Debugging with GDB: Command Syntax</title> 18 19<meta name="description" content="Debugging with GDB: Command Syntax"> 20<meta name="keywords" content="Debugging with GDB: Command Syntax"> 21<meta name="resource-type" content="document"> 22<meta name="distribution" content="global"> 23<meta name="Generator" content="makeinfo"> 24<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 25<link href="index.html#Top" rel="start" title="Top"> 26<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index"> 27<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> 28<link href="Commands.html#Commands" rel="up" title="Commands"> 29<link href="Command-Settings.html#Command-Settings" rel="next" title="Command Settings"> 30<link href="Commands.html#Commands" rel="previous" title="Commands"> 31<style type="text/css"> 32<!-- 33a.summary-letter {text-decoration: none} 34blockquote.smallquotation {font-size: smaller} 35div.display {margin-left: 3.2em} 36div.example {margin-left: 3.2em} 37div.indentedblock {margin-left: 3.2em} 38div.lisp {margin-left: 3.2em} 39div.smalldisplay {margin-left: 3.2em} 40div.smallexample {margin-left: 3.2em} 41div.smallindentedblock {margin-left: 3.2em; font-size: smaller} 42div.smalllisp {margin-left: 3.2em} 43kbd {font-style:oblique} 44pre.display {font-family: inherit} 45pre.format {font-family: inherit} 46pre.menu-comment {font-family: serif} 47pre.menu-preformatted {font-family: serif} 48pre.smalldisplay {font-family: inherit; font-size: smaller} 49pre.smallexample {font-size: smaller} 50pre.smallformat {font-family: inherit; font-size: smaller} 51pre.smalllisp {font-size: smaller} 52span.nocodebreak {white-space:nowrap} 53span.nolinebreak {white-space:nowrap} 54span.roman {font-family:serif; font-weight:normal} 55span.sansserif {font-family:sans-serif; font-weight:normal} 56ul.no-bullet {list-style: none} 57--> 58</style> 59 60 61</head> 62 63<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> 64<a name="Command-Syntax"></a> 65<div class="header"> 66<p> 67Next: <a href="Command-Settings.html#Command-Settings" accesskey="n" rel="next">Command Settings</a>, Up: <a href="Commands.html#Commands" accesskey="u" rel="up">Commands</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> 68</div> 69<hr> 70<a name="Command-Syntax-1"></a> 71<h3 class="section">3.1 Command Syntax</h3> 72 73<p>A <small>GDB</small> command is a single line of input. There is no limit on 74how long it can be. It starts with a command name, which is followed by 75arguments whose meaning depends on the command name. For example, the 76command <code>step</code> accepts an argument which is the number of times to 77step, as in ‘<samp>step 5</samp>’. You can also use the <code>step</code> command 78with no arguments. Some commands do not allow any arguments. 79</p> 80<a name="index-abbreviation"></a> 81<p><small>GDB</small> command names may always be truncated if that abbreviation is 82unambiguous. Other possible command abbreviations are listed in the 83documentation for individual commands. In some cases, even ambiguous 84abbreviations are allowed; for example, <code>s</code> is specially defined as 85equivalent to <code>step</code> even though there are other commands whose 86names start with <code>s</code>. You can test abbreviations by using them as 87arguments to the <code>help</code> command. 88</p> 89<a name="index-repeating-commands"></a> 90<a name="index-RET-_0028repeat-last-command_0029"></a> 91<p>A blank line as input to <small>GDB</small> (typing just <tt class="key">RET</tt>) means to 92repeat the previous command. Certain commands (for example, <code>run</code>) 93will not repeat this way; these are commands whose unintentional 94repetition might cause trouble and which you are unlikely to want to 95repeat. User-defined commands can disable this feature; see 96<a href="Define.html#Define">dont-repeat</a>. 97</p> 98<p>The <code>list</code> and <code>x</code> commands, when you repeat them with 99<tt class="key">RET</tt>, construct new arguments rather than repeating 100exactly as typed. This permits easy scanning of source or memory. 101</p> 102<p><small>GDB</small> can also use <tt class="key">RET</tt> in another way: to partition lengthy 103output, in a way similar to the common utility <code>more</code> 104(see <a href="Screen-Size.html#Screen-Size">Screen Size</a>). Since it is easy to press one 105<tt class="key">RET</tt> too many in this situation, <small>GDB</small> disables command 106repetition after any command that generates this sort of display. 107</p> 108<a name="index-_0023-_0028a-comment_0029"></a> 109<a name="index-comment"></a> 110<p>Any text from a <kbd>#</kbd> to the end of the line is a comment; it does 111nothing. This is useful mainly in command files (see <a href="Command-Files.html#Command-Files">Command Files</a>). 112</p> 113<a name="index-repeating-command-sequences"></a> 114<a name="index-Ctrl_002do-_0028operate_002dand_002dget_002dnext_0029"></a> 115<p>The <kbd>Ctrl-o</kbd> binding is useful for repeating a complex sequence of 116commands. This command accepts the current line, like <tt class="key">RET</tt>, and 117then fetches the next line relative to the current line from the history 118for editing. 119</p> 120 121<hr> 122<div class="header"> 123<p> 124Next: <a href="Command-Settings.html#Command-Settings" accesskey="n" rel="next">Command Settings</a>, Up: <a href="Commands.html#Commands" accesskey="u" rel="up">Commands</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> 125</div> 126 127 128 129</body> 130</html> 131