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| <h3 class="section">3.1 Command Syntax</h3> |
| |
| <p>A <span class="sc">gdb</span> command is a single line of input. There is no limit on |
| how long it can be. It starts with a command name, which is followed by |
| arguments whose meaning depends on the command name. For example, the |
| command <code>step</code> accepts an argument which is the number of times to |
| step, as in ‘<samp><span class="samp">step 5</span></samp>’. You can also use the <code>step</code> command |
| with no arguments. Some commands do not allow any arguments. |
| |
| <p><a name="index-abbreviation-68"></a><span class="sc">gdb</span> command names may always be truncated if that abbreviation is |
| unambiguous. Other possible command abbreviations are listed in the |
| documentation for individual commands. In some cases, even ambiguous |
| abbreviations are allowed; for example, <code>s</code> is specially defined as |
| equivalent to <code>step</code> even though there are other commands whose |
| names start with <code>s</code>. You can test abbreviations by using them as |
| arguments to the <code>help</code> command. |
| |
| <p><a name="index-repeating-commands-69"></a><a name="index-RET-_0040r_007b_0028repeat-last-command_0029_007d-70"></a>A blank line as input to <span class="sc">gdb</span> (typing just <RET>) means to |
| repeat the previous command. Certain commands (for example, <code>run</code>) |
| will not repeat this way; these are commands whose unintentional |
| repetition might cause trouble and which you are unlikely to want to |
| repeat. User-defined commands can disable this feature; see |
| <a href="Define.html#Define">dont-repeat</a>. |
| |
| <p>The <code>list</code> and <code>x</code> commands, when you repeat them with |
| <RET>, construct new arguments rather than repeating |
| exactly as typed. This permits easy scanning of source or memory. |
| |
| <p><span class="sc">gdb</span> can also use <RET> in another way: to partition lengthy |
| output, in a way similar to the common utility <code>more</code> |
| (see <a href="Screen-Size.html#Screen-Size">Screen Size</a>). Since it is easy to press one |
| <RET> too many in this situation, <span class="sc">gdb</span> disables command |
| repetition after any command that generates this sort of display. |
| |
| <p><a name="index-g_t_0023-_0040r_007b_0028a-comment_0029_007d-71"></a><a name="index-comment-72"></a>Any text from a <kbd>#</kbd> to the end of the line is a comment; it does |
| nothing. This is useful mainly in command files (see <a href="Command-Files.html#Command-Files">Command Files</a>). |
| |
| <p><a name="index-repeating-command-sequences-73"></a><a name="index-Ctrl_002do-_0040r_007b_0028operate_002dand_002dget_002dnext_0029_007d-74"></a>The <kbd>Ctrl-o</kbd> binding is useful for repeating a complex sequence of |
| commands. This command accepts the current line, like <RET>, and |
| then fetches the next line relative to the current line from the history |
| for editing. |
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