91 lines
4.8 KiB
HTML
91 lines
4.8 KiB
HTML
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<html lang="en">
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<head>
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<title>Command Syntax - 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="Commands.html#Commands" title="Commands">
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<link rel="next" href="Completion.html#Completion" title="Completion">
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Copyright (C) 1988-2019 Free Software Foundation, Inc.
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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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Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
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and with the Back-Cover Texts as in (a) below.
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</head>
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<body>
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<div class="node">
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<a name="Command-Syntax"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Completion.html#Completion">Completion</a>,
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Up: <a rel="up" accesskey="u" href="Commands.html#Commands">Commands</a>
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<hr>
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</div>
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<h3 class="section">3.1 Command Syntax</h3>
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<p>A <span class="sc">gdb</span> command is a single line of input. There is no limit on
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how long it can be. It starts with a command name, which is followed by
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arguments whose meaning depends on the command name. For example, the
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command <code>step</code> accepts an argument which is the number of times to
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step, as in ‘<samp><span class="samp">step 5</span></samp>’. You can also use the <code>step</code> command
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with no arguments. Some commands do not allow any arguments.
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<p><a name="index-abbreviation-77"></a><span class="sc">gdb</span> command names may always be truncated if that abbreviation is
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unambiguous. Other possible command abbreviations are listed in the
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documentation for individual commands. In some cases, even ambiguous
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abbreviations are allowed; for example, <code>s</code> is specially defined as
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equivalent to <code>step</code> even though there are other commands whose
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names start with <code>s</code>. You can test abbreviations by using them as
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arguments to the <code>help</code> command.
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<p><a name="index-repeating-commands-78"></a><a name="index-RET-_0040r_007b_0028repeat-last-command_0029_007d-79"></a>A blank line as input to <span class="sc">gdb</span> (typing just <RET>) means to
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repeat the previous command. Certain commands (for example, <code>run</code>)
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will not repeat this way; these are commands whose unintentional
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repetition might cause trouble and which you are unlikely to want to
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repeat. User-defined commands can disable this feature; see
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<a href="Define.html#Define">dont-repeat</a>.
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<p>The <code>list</code> and <code>x</code> commands, when you repeat them with
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<RET>, construct new arguments rather than repeating
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exactly as typed. This permits easy scanning of source or memory.
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<p><span class="sc">gdb</span> can also use <RET> in another way: to partition lengthy
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output, in a way similar to the common utility <code>more</code>
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(see <a href="Screen-Size.html#Screen-Size">Screen Size</a>). Since it is easy to press one
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<RET> too many in this situation, <span class="sc">gdb</span> disables command
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repetition after any command that generates this sort of display.
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<p><a name="index-g_t_0023-_0040r_007b_0028a-comment_0029_007d-80"></a><a name="index-comment-81"></a>Any text from a <kbd>#</kbd> to the end of the line is a comment; it does
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nothing. This is useful mainly in command files (see <a href="Command-Files.html#Command-Files">Command Files</a>).
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<p><a name="index-repeating-command-sequences-82"></a><a name="index-Ctrl_002do-_0040r_007b_0028operate_002dand_002dget_002dnext_0029_007d-83"></a>The <kbd>Ctrl-o</kbd> binding is useful for repeating a complex sequence of
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commands. This command accepts the current line, like <RET>, and
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then fetches the next line relative to the current line from the history
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for editing.
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</body></html>
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