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| <h3 class="heading">gdb man</h3> |
| |
| <!-- man title gdb The GNU Debugger --> |
| <!-- man begin SYNOPSIS gdb --> |
| <p>gdb [<samp><span class="option">-help</span></samp>] [<samp><span class="option">-nh</span></samp>] [<samp><span class="option">-nx</span></samp>] [<samp><span class="option">-q</span></samp>] |
| [<samp><span class="option">-batch</span></samp>] [<samp><span class="option">-cd=</span></samp><var>dir</var>] [<samp><span class="option">-f</span></samp>] |
| [<samp><span class="option">-b</span></samp> <!-- /@w --><var>bps</var>] |
| [<samp><span class="option">-tty=</span></samp><var>dev</var>] [<samp><span class="option">-s</span></samp> <var>symfile</var>] |
| [<samp><span class="option">-e</span></samp> <!-- /@w --><var>prog</var>] [<samp><span class="option">-se</span></samp> <!-- /@w --><var>prog</var>] |
| [<samp><span class="option">-c</span></samp> <!-- /@w --><var>core</var>] [<samp><span class="option">-p</span></samp> <!-- /@w --><var>procID</var>] |
| [<samp><span class="option">-x</span></samp> <!-- /@w --><var>cmds</var>] [<samp><span class="option">-d</span></samp> <!-- /@w --><var>dir</var>] |
| [<var>prog</var>|<var>prog</var> <var>procID</var>|<var>prog</var> <var>core</var>] |
| <!-- man end --> |
| |
| <!-- man begin DESCRIPTION gdb --> |
| <p>The purpose of a debugger such as <span class="sc">gdb</span> is to allow you to see what is |
| going on “inside” another program while it executes – or what another |
| program was doing at the moment it crashed. |
| |
| <p><span class="sc">gdb</span> can do four main kinds of things (plus other things in support of |
| these) to help you catch bugs in the act: |
| |
| <ul> |
| <li>Start your program, specifying anything that might affect its behavior. |
| |
| <li>Make your program stop on specified conditions. |
| |
| <li>Examine what has happened, when your program has stopped. |
| |
| <li>Change things in your program, so you can experiment with correcting the |
| effects of one bug and go on to learn about another. |
| </ul> |
| |
| <p>You can use <span class="sc">gdb</span> to debug programs written in C, C<tt>++</tt>, Fortran and |
| Modula-2. |
| |
| <p><span class="sc">gdb</span> is invoked with the shell command <code>gdb</code>. Once started, it reads |
| commands from the terminal until you tell it to exit with the <span class="sc">gdb</span> |
| command <code>quit</code>. You can get online help from <span class="sc">gdb</span> itself |
| by using the command <code>help</code>. |
| |
| <p>You can run <code>gdb</code> with no arguments or options; but the most |
| usual way to start <span class="sc">gdb</span> is with one argument or two, specifying an |
| executable program as the argument: |
| |
| <pre class="smallexample"> gdb program |
| </pre> |
| <p>You can also start with both an executable program and a core file specified: |
| |
| <pre class="smallexample"> gdb program core |
| </pre> |
| <p>You can, instead, specify a process ID as a second argument, if you want |
| to debug a running process: |
| |
| <pre class="smallexample"> gdb program 1234 |
| gdb -p 1234 |
| </pre> |
| <p class="noindent">would attach <span class="sc">gdb</span> to process <code>1234</code> (unless you also have a file |
| named <samp><span class="file">1234</span></samp>; <span class="sc">gdb</span> does check for a core file first). |
| With option <samp><span class="option">-p</span></samp> you can omit the <var>program</var> filename. |
| |
| <p>Here are some of the most frequently needed <span class="sc">gdb</span> commands: |
| |
| <!-- pod2man highlights the right hand side of the @item lines. --> |
| <dl> |
| <dt><samp><span class="env">break [</span><var>file</var><span class="env">:]</span><var>function</var></samp><dd>Set a breakpoint at <var>function</var> (in <var>file</var>). |
| |
| <br><dt><samp><span class="env">run [</span><var>arglist</var><span class="env">]</span></samp><dd>Start your program (with <var>arglist</var>, if specified). |
| |
| <br><dt><samp><span class="env">bt</span></samp><dd>Backtrace: display the program stack. |
| |
| <br><dt><samp><span class="env">print </span><var>expr</var></samp><dd>Display the value of an expression. |
| |
| <br><dt><samp><span class="env">c</span></samp><dd>Continue running your program (after stopping, e.g. at a breakpoint). |
| |
| <br><dt><samp><span class="env">next</span></samp><dd>Execute next program line (after stopping); step <em>over</em> any |
| function calls in the line. |
| |
| <br><dt><samp><span class="env">edit [</span><var>file</var><span class="env">:]</span><var>function</var></samp><dd>look at the program line where it is presently stopped. |
| |
| <br><dt><samp><span class="env">list [</span><var>file</var><span class="env">:]</span><var>function</var></samp><dd>type the text of the program in the vicinity of where it is presently stopped. |
| |
| <br><dt><samp><span class="env">step</span></samp><dd>Execute next program line (after stopping); step <em>into</em> any |
| function calls in the line. |
| |
| <br><dt><samp><span class="env">help [</span><var>name</var><span class="env">]</span></samp><dd>Show information about <span class="sc">gdb</span> command <var>name</var>, or general information |
| about using <span class="sc">gdb</span>. |
| |
| <br><dt><samp><span class="env">quit</span></samp><dd>Exit from <span class="sc">gdb</span>. |
| </dl> |
| |
| <!-- man end --> |
| <!-- man begin OPTIONS gdb --> |
| <p>Any arguments other than options specify an executable |
| file and core file (or process ID); that is, the first argument |
| encountered with no |
| associated option flag is equivalent to a <samp><span class="option">-se</span></samp> option, and the second, |
| if any, is equivalent to a <samp><span class="option">-c</span></samp> option if it's the name of a file. |
| Many options have |
| both long and short forms; both are shown here. The long forms are also |
| recognized if you truncate them, so long as enough of the option is |
| present to be unambiguous. (If you prefer, you can flag option |
| arguments with <samp><span class="option">+</span></samp> rather than <samp><span class="option">-</span></samp>, though we illustrate the |
| more usual convention.) |
| |
| <p>All the options and command line arguments you give are processed |
| in sequential order. The order makes a difference when the <samp><span class="option">-x</span></samp> |
| option is used. |
| |
| <dl> |
| <dt><samp><span class="env">-help</span></samp><dt><samp><span class="env">-h</span></samp><dd>List all options, with brief explanations. |
| |
| <br><dt><samp><span class="env">-symbols=</span><var>file</var></samp><dt><samp><span class="env">-s </span><var>file</var></samp><dd>Read symbol table from file <var>file</var>. |
| |
| <br><dt><samp><span class="env">-write</span></samp><dd>Enable writing into executable and core files. |
| |
| <br><dt><samp><span class="env">-exec=</span><var>file</var></samp><dt><samp><span class="env">-e </span><var>file</var></samp><dd>Use file <var>file</var> as the executable file to execute when |
| appropriate, and for examining pure data in conjunction with a core |
| dump. |
| |
| <br><dt><samp><span class="env">-se=</span><var>file</var></samp><dd>Read symbol table from file <var>file</var> and use it as the executable |
| file. |
| |
| <br><dt><samp><span class="env">-core=</span><var>file</var></samp><dt><samp><span class="env">-c </span><var>file</var></samp><dd>Use file <var>file</var> as a core dump to examine. |
| |
| <br><dt><samp><span class="env">-command=</span><var>file</var></samp><dt><samp><span class="env">-x </span><var>file</var></samp><dd>Execute <span class="sc">gdb</span> commands from file <var>file</var>. |
| |
| <br><dt><samp><span class="env">-ex </span><var>command</var></samp><dd>Execute given <span class="sc">gdb</span> <var>command</var>. |
| |
| <br><dt><samp><span class="env">-directory=</span><var>directory</var></samp><dt><samp><span class="env">-d </span><var>directory</var></samp><dd>Add <var>directory</var> to the path to search for source files. |
| |
| <br><dt><samp><span class="env">-nh</span></samp><dd>Do not execute commands from <samp><span class="file">~/.gdbinit</span></samp>. |
| |
| <br><dt><samp><span class="env">-nx</span></samp><dt><samp><span class="env">-n</span></samp><dd>Do not execute commands from any <samp><span class="file">.gdbinit</span></samp> initialization files. |
| |
| <br><dt><samp><span class="env">-quiet</span></samp><dt><samp><span class="env">-q</span></samp><dd>“Quiet”. Do not print the introductory and copyright messages. These |
| messages are also suppressed in batch mode. |
| |
| <br><dt><samp><span class="env">-batch</span></samp><dd>Run in batch mode. Exit with status <code>0</code> after processing all the command |
| files specified with <samp><span class="option">-x</span></samp> (and <samp><span class="file">.gdbinit</span></samp>, if not inhibited). |
| Exit with nonzero status if an error occurs in executing the <span class="sc">gdb</span> |
| commands in the command files. |
| |
| <p>Batch mode may be useful for running <span class="sc">gdb</span> as a filter, for example to |
| download and run a program on another computer; in order to make this |
| more useful, the message |
| |
| <pre class="smallexample"> Program exited normally. |
| </pre> |
| <p class="noindent">(which is ordinarily issued whenever a program running under <span class="sc">gdb</span> control |
| terminates) is not issued when running in batch mode. |
| |
| <br><dt><samp><span class="env">-cd=</span><var>directory</var></samp><dd>Run <span class="sc">gdb</span> using <var>directory</var> as its working directory, |
| instead of the current directory. |
| |
| <br><dt><samp><span class="env">-fullname</span></samp><dt><samp><span class="env">-f</span></samp><dd>Emacs sets this option when it runs <span class="sc">gdb</span> as a subprocess. It tells |
| <span class="sc">gdb</span> to output the full file name and line number in a standard, |
| recognizable fashion each time a stack frame is displayed (which |
| includes each time the program stops). This recognizable format looks |
| like two ‘<samp><span class="samp">\032</span></samp>’ characters, followed by the file name, line number |
| and character position separated by colons, and a newline. The |
| Emacs-to-<span class="sc">gdb</span> interface program uses the two ‘<samp><span class="samp">\032</span></samp>’ |
| characters as a signal to display the source code for the frame. |
| |
| <br><dt><samp><span class="env">-b </span><var>bps</var></samp><dd>Set the line speed (baud rate or bits per second) of any serial |
| interface used by <span class="sc">gdb</span> for remote debugging. |
| |
| <br><dt><samp><span class="env">-tty=</span><var>device</var></samp><dd>Run using <var>device</var> for your program's standard input and output. |
| </dl> |
| <!-- man end --> |
| |
| <!-- man begin SEEALSO gdb --> |
| <!-- man end --> |
| </body></html> |
| |
