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| <h4 class="subsection">23.1.3 Command Files</h4> |
| |
| <p><a name="index-command-files-1552"></a><a name="index-scripting-commands-1553"></a>A command file for <span class="sc">gdb</span> is a text file made of lines that are |
| <span class="sc">gdb</span> commands. Comments (lines starting with <kbd>#</kbd>) may |
| also be included. An empty line in a command file does nothing; it |
| does not mean to repeat the last command, as it would from the |
| terminal. |
| |
| <p>You can request the execution of a command file with the <code>source</code> |
| command. Note that the <code>source</code> command is also used to evaluate |
| scripts that are not Command Files. The exact behavior can be configured |
| using the <code>script-extension</code> setting. |
| See <a href="Extending-GDB.html#Extending-GDB">Extending GDB</a>. |
| |
| |
| <a name="index-source-1554"></a> |
| <a name="index-execute-commands-from-a-file-1555"></a> |
| <dl><dt><code>source [-s] [-v] </code><var>filename</var><dd>Execute the command file <var>filename</var>. |
| </dl> |
| |
| <p>The lines in a command file are generally executed sequentially, |
| unless the order of execution is changed by one of the |
| <em>flow-control commands</em> described below. The commands are not |
| printed as they are executed. An error in any command terminates |
| execution of the command file and control is returned to the console. |
| |
| <p><span class="sc">gdb</span> first searches for <var>filename</var> in the current directory. |
| If the file is not found there, and <var>filename</var> does not specify a |
| directory, then <span class="sc">gdb</span> also looks for the file on the source search path |
| (specified with the ‘<samp><span class="samp">directory</span></samp>’ command); |
| except that <samp><span class="file">$cdir</span></samp> is not searched because the compilation directory |
| is not relevant to scripts. |
| |
| <p>If <code>-s</code> is specified, then <span class="sc">gdb</span> searches for <var>filename</var> |
| on the search path even if <var>filename</var> specifies a directory. |
| The search is done by appending <var>filename</var> to each element of the |
| search path. So, for example, if <var>filename</var> is <samp><span class="file">mylib/myscript</span></samp> |
| and the search path contains <samp><span class="file">/home/user</span></samp> then <span class="sc">gdb</span> will |
| look for the script <samp><span class="file">/home/user/mylib/myscript</span></samp>. |
| The search is also done if <var>filename</var> is an absolute path. |
| For example, if <var>filename</var> is <samp><span class="file">/tmp/myscript</span></samp> and |
| the search path contains <samp><span class="file">/home/user</span></samp> then <span class="sc">gdb</span> will |
| look for the script <samp><span class="file">/home/user/tmp/myscript</span></samp>. |
| For DOS-like systems, if <var>filename</var> contains a drive specification, |
| it is stripped before concatenation. For example, if <var>filename</var> is |
| <samp><span class="file">d:myscript</span></samp> and the search path contains <samp><span class="file">c:/tmp</span></samp> then <span class="sc">gdb</span> |
| will look for the script <samp><span class="file">c:/tmp/myscript</span></samp>. |
| |
| <p>If <code>-v</code>, for verbose mode, is given then <span class="sc">gdb</span> displays |
| each command as it is executed. The option must be given before |
| <var>filename</var>, and is interpreted as part of the filename anywhere else. |
| |
| <p>Commands that would ask for confirmation if used interactively proceed |
| without asking when used in a command file. Many <span class="sc">gdb</span> commands that |
| normally print messages to say what they are doing omit the messages |
| when called from command files. |
| |
| <p><span class="sc">gdb</span> also accepts command input from standard input. In this |
| mode, normal output goes to standard output and error output goes to |
| standard error. Errors in a command file supplied on standard input do |
| not terminate execution of the command file—execution continues with |
| the next command. |
| |
| <pre class="smallexample"> gdb < cmds > log 2>&1 |
| </pre> |
| <p>(The syntax above will vary depending on the shell used.) This example |
| will execute commands from the file <samp><span class="file">cmds</span></samp>. All output and errors |
| would be directed to <samp><span class="file">log</span></samp>. |
| |
| <p>Since commands stored on command files tend to be more general than |
| commands typed interactively, they frequently need to deal with |
| complicated situations, such as different or unexpected values of |
| variables and symbols, changes in how the program being debugged is |
| built, etc. <span class="sc">gdb</span> provides a set of flow-control commands to |
| deal with these complexities. Using these commands, you can write |
| complex scripts that loop over data structures, execute commands |
| conditionally, etc. |
| |
| |
| <a name="index-if-1556"></a> |
| <a name="index-else-1557"></a> |
| <dl><dt><code>if</code><dt><code>else</code><dd>This command allows to include in your script conditionally executed |
| commands. The <code>if</code> command takes a single argument, which is an |
| expression to evaluate. It is followed by a series of commands that |
| are executed only if the expression is true (its value is nonzero). |
| There can then optionally be an <code>else</code> line, followed by a series |
| of commands that are only executed if the expression was false. The |
| end of the list is marked by a line containing <code>end</code>. |
| |
| <p><a name="index-while-1558"></a><br><dt><code>while</code><dd>This command allows to write loops. Its syntax is similar to |
| <code>if</code>: the command takes a single argument, which is an expression |
| to evaluate, and must be followed by the commands to execute, one per |
| line, terminated by an <code>end</code>. These commands are called the |
| <dfn>body</dfn> of the loop. The commands in the body of <code>while</code> are |
| executed repeatedly as long as the expression evaluates to true. |
| |
| <p><a name="index-loop_005fbreak-1559"></a><br><dt><code>loop_break</code><dd>This command exits the <code>while</code> loop in whose body it is included. |
| Execution of the script continues after that <code>while</code>s <code>end</code> |
| line. |
| |
| <p><a name="index-loop_005fcontinue-1560"></a><br><dt><code>loop_continue</code><dd>This command skips the execution of the rest of the body of commands |
| in the <code>while</code> loop in whose body it is included. Execution |
| branches to the beginning of the <code>while</code> loop, where it evaluates |
| the controlling expression. |
| |
| <p><a name="index-end_0040r_007b-_0028if_002felse_002fwhile-commands_0029_007d-1561"></a><br><dt><code>end</code><dd>Terminate the block of commands that are the body of <code>if</code>, |
| <code>else</code>, or <code>while</code> flow-control commands. |
| </dl> |
| |
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