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| <h3 class="section">22.3 Command History</h3> |
| |
| <p><a name="index-command-history-1660"></a> |
| <span class="sc">gdb</span> can keep track of the commands you type during your |
| debugging sessions, so that you can be certain of precisely what |
| happened. Use these commands to manage the <span class="sc">gdb</span> command |
| history facility. |
| |
| <p><span class="sc">gdb</span> uses the <span class="sc">gnu</span> History library, a part of the Readline |
| package, to provide the history facility. |
| See <a href="Using-History-Interactively.html#Using-History-Interactively">Using History Interactively</a>, |
| for the detailed description of the History library. |
| |
| <p>To issue a command to <span class="sc">gdb</span> without affecting certain aspects of |
| the state which is seen by users, prefix it with ‘<samp><span class="samp">server </span></samp>’ |
| (see <a href="Server-Prefix.html#Server-Prefix">Server Prefix</a>). This |
| means that this command will not affect the command history, nor will it |
| affect <span class="sc">gdb</span>'s notion of which command to repeat if <RET> is |
| pressed on a line by itself. |
| |
| <p><a name="index-g_t_0040code_007bserver_007d_002c-command-prefix-1661"></a>The server prefix does not affect the recording of values into the value |
| history; to print a value without recording it into the value history, |
| use the <code>output</code> command instead of the <code>print</code> command. |
| |
| <p>Here is the description of <span class="sc">gdb</span> commands related to command |
| history. |
| |
| |
| <a name="index-history-substitution-1662"></a> |
| <a name="index-history-file-1663"></a> |
| <a name="index-set-history-filename-1664"></a> |
| <a name="index-g_t_0040env_007bGDBHISTFILE_007d_002c-environment-variable-1665"></a> |
| <dl><dt><code>set history filename </code><var>fname</var><dd>Set the name of the <span class="sc">gdb</span> command history file to <var>fname</var>. |
| This is the file where <span class="sc">gdb</span> reads an initial command history |
| list, and where it writes the command history from this session when it |
| exits. You can access this list through history expansion or through |
| the history command editing characters listed below. This file defaults |
| to the value of the environment variable <code>GDBHISTFILE</code>, or to |
| <samp><span class="file">./.gdb_history</span></samp> (<samp><span class="file">./_gdb_history</span></samp> on MS-DOS) if this variable |
| is not set. |
| |
| <p><a name="index-save-command-history-1666"></a><a name="index-set-history-save-1667"></a><br><dt><code>set history save</code><dt><code>set history save on</code><dd>Record command history in a file, whose name may be specified with the |
| <code>set history filename</code> command. By default, this option is disabled. |
| |
| <br><dt><code>set history save off</code><dd>Stop recording command history in a file. |
| |
| <p><a name="index-history-size-1668"></a><a name="index-set-history-size-1669"></a><a name="index-g_t_0040env_007bGDBHISTSIZE_007d_002c-environment-variable-1670"></a><br><dt><code>set history size </code><var>size</var><dt><code>set history size unlimited</code><dd>Set the number of commands which <span class="sc">gdb</span> keeps in its history list. |
| This defaults to the value of the environment variable <samp><span class="env">GDBHISTSIZE</span></samp>, or |
| to 256 if this variable is not set. Non-numeric values of <samp><span class="env">GDBHISTSIZE</span></samp> |
| are ignored. If <var>size</var> is <code>unlimited</code> or if <samp><span class="env">GDBHISTSIZE</span></samp> is |
| either a negative number or the empty string, then the number of commands |
| <span class="sc">gdb</span> keeps in the history list is unlimited. |
| |
| <p><a name="index-remove-duplicate-history-1671"></a><a name="index-set-history-remove_002dduplicates-1672"></a><br><dt><code>set history remove-duplicates </code><var>count</var><dt><code>set history remove-duplicates unlimited</code><dd>Control the removal of duplicate history entries in the command history list. |
| If <var>count</var> is non-zero, <span class="sc">gdb</span> will look back at the last <var>count</var> |
| history entries and remove the first entry that is a duplicate of the current |
| entry being added to the command history list. If <var>count</var> is |
| <code>unlimited</code> then this lookbehind is unbounded. If <var>count</var> is 0, then |
| removal of duplicate history entries is disabled. |
| |
| <p>Only history entries added during the current session are considered for |
| removal. This option is set to 0 by default. |
| |
| </dl> |
| |
| <p>History expansion assigns special meaning to the character <kbd>!</kbd>. |
| See <a href="Event-Designators.html#Event-Designators">Event Designators</a>, |
| for more details. |
| |
| <p><a name="index-history-expansion_002c-turn-on_002foff-1673"></a>Since <kbd>!</kbd> is also the logical not operator in C, history expansion |
| is off by default. If you decide to enable history expansion with the |
| <code>set history expansion on</code> command, you may sometimes need to |
| follow <kbd>!</kbd> (when it is used as logical not, in an expression) with |
| a space or a tab to prevent it from being expanded. The readline |
| history facilities do not attempt substitution on the strings |
| <kbd>!=</kbd> and <kbd>!(</kbd>, even when history expansion is enabled. |
| |
| <p>The commands to control history expansion are: |
| |
| <dl> |
| <dt><code>set history expansion on</code><dt><code>set history expansion</code><dd><a name="index-set-history-expansion-1674"></a>Enable history expansion. History expansion is off by default. |
| |
| <br><dt><code>set history expansion off</code><dd>Disable history expansion. |
| |
| <!-- @group --> |
| <p><a name="index-show-history-1675"></a><br><dt><code>show history</code><dt><code>show history filename</code><dt><code>show history save</code><dt><code>show history size</code><dt><code>show history expansion</code><dd>These commands display the state of the <span class="sc">gdb</span> history parameters. |
| <code>show history</code> by itself displays all four states. |
| <!-- @end group --> |
| </dl> |
| |
| |
| <a name="index-show-commands-1676"></a> |
| <a name="index-show-last-commands-1677"></a> |
| <a name="index-display-command-history-1678"></a> |
| <dl><dt><code>show commands</code><dd>Display the last ten commands in the command history. |
| |
| <br><dt><code>show commands </code><var>n</var><dd>Print ten commands centered on command number <var>n</var>. |
| |
| <br><dt><code>show commands +</code><dd>Print ten commands just after the commands last printed. |
| </dl> |
| |
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