gdb(1) — Linux manual page


GDB(1)                    GNU Development Tools                   GDB(1)

NAME         top

       gdb - The GNU Debugger

SYNOPSIS         top

       gdb [OPTIONS] [prog|prog procID|prog core]

DESCRIPTION         top

       The purpose of a debugger such as GDB 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.

       GDB can do four main kinds of things (plus other things in
       support of these) to help you catch bugs in the act:

       •   Start your program, specifying anything that might affect its

       •   Make your program stop on specified conditions.

       •   Examine what has happened, when your program has stopped.

       •   Change things in your program, so you can experiment with
           correcting the effects of one bug and go on to learn about

       You can use GDB to debug programs written in C, C++, Fortran and

       GDB is invoked with the shell command "gdb".  Once started, it
       reads commands from the terminal until you tell it to exit with
       the GDB command "quit" or "exit".  You can get online help from
       GDB itself by using the command "help".

       You can run "gdb" with no arguments or options; but the most
       usual way to start GDB is with one argument or two, specifying an
       executable program as the argument:

               gdb program

       You can also start with both an executable program and a core
       file specified:

               gdb program core

       You can, instead, specify a process ID as a second argument or
       use option "-p", if you want to debug a running process:

               gdb program 1234
               gdb -p 1234

       would attach GDB to process 1234.  With option -p you can omit
       the program filename.

       Here are some of the most frequently needed GDB commands:

       break [file:][function|line]
           Set a breakpoint at function or line (in file).

       run [arglist]
           Start your program (with arglist, if specified).

       bt  Backtrace: display the program stack.

       print expr
           Display the value of an expression.

       c   Continue running your program (after stopping, e.g. at a

           Execute next program line (after stopping); step over any
           function calls in the line.

       edit [file:]function
           look at the program line where it is presently stopped.

       list [file:]function
           type the text of the program in the vicinity of where it is
           presently stopped.

           Execute next program line (after stopping); step into any
           function calls in the line.

       help [name]
           Show information about GDB command name, or general
           information about using GDB.

           Exit from GDB.

       For full details on GDB, see Using GDB: A Guide to the GNU
       Source-Level Debugger, by Richard M. Stallman and Roland H.
       Pesch.  The same text is available online as the "gdb" entry in
       the "info" program.

OPTIONS         top

       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
       --se option, and the second, if any, is equivalent to a -c option
       if it's the name of a file.  Many options have both long and
       abbreviated 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.

       The abbreviated forms are shown here with - and long forms are
       shown with -- to reflect how they are shown in --help. However,
       GDB recognizes all of the following conventions for most options:

       "--option value"
       "-option value"
       "--o value"
       "-o value"

       All the options and command line arguments you give are processed
       in sequential order.  The order makes a difference when the -x
       option is used.

       -h  List all options, with brief explanations.

       -s file
           Read symbol table from file.

           Enable writing into executable and core files.

       -e file
           Use file as the executable file to execute when appropriate,
           and for examining pure data in conjunction with a core dump.

           Read symbol table from file and use it as the executable

       -c file
           Use file as a core dump to examine.

       -x file
           Execute GDB commands from file.

       -ex command
           Execute given GDB command.

           Execute GDB command before loading the inferior.

       -d directory
           Add directory to the path to search for source files.

           Do not execute commands from ~/.config/gdb/gdbinit,
           ~/.gdbinit, ~/.config/gdb/gdbearlyinit, or ~/.gdbearlyinit

       -n  Do not execute commands from any .gdbinit or .gdbearlyinit
           initialization files.

       -q  "Quiet".  Do not print the introductory and copyright
           messages.  These messages are also suppressed in batch mode.

           Run in batch mode.  Exit with status 0 after processing all
           the command files specified with -x (and .gdbinit, if not
           inhibited).  Exit with nonzero status if an error occurs in
           executing the GDB commands in the command files.

           Batch mode may be useful for running GDB as a filter, for
           example to download and run a program on another computer; in
           order to make this more useful, the message

                   Program exited normally.

           (which is ordinarily issued whenever a program running under
           GDB control terminates) is not issued when running in batch

           Run in batch mode, just like --batch, but totally silent.
           All GDB output is suppressed (stderr is unaffected).  This is
           much quieter than --silent and would be useless for an
           interactive session.

           This is particularly useful when using targets that give
           Loading section messages, for example.

           Note that targets that give their output via GDB, as opposed
           to writing directly to "stdout", will also be made silent.

       --args prog [arglist]
           Change interpretation of command line so that arguments
           following this option are passed as arguments to the
           inferior.  As an example, take the following command:

                   gdb ./a.out -q

           It would start GDB with -q, not printing the introductory
           message.  On the other hand, using:

                   gdb --args ./a.out -q

           starts GDB with the introductory message, and passes the
           option to the inferior.

           Attach GDB to an already running program, with the PID pid.

           Open the terminal user interface.

           Read all symbols from the given symfile on the first access.

           Do not read symbol files.

           GDB's exit code will be the same as the child's exit code.

           Print details about GDB configuration and then exit.

           Print version information and then exit.

           Run GDB using directory as its working directory, instead of
           the current directory.

       -D  Run GDB using directory as its data directory.  The data
           directory is where GDB searches for its auxiliary files.

       -f  Emacs sets this option when it runs GDB as a subprocess.  It
           tells GDB 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 \032 characters, followed
           by the file name, line number and character position
           separated by colons, and a newline.  The Emacs-to-GDB
           interface program uses the two \032 characters as a signal to
           display the source code for the frame.

       -b baudrate
           Set the line speed (baud rate or bits per second) of any
           serial interface used by GDB for remote debugging.

       -l timeout
           Set timeout, in seconds, for remote debugging.

           Run using device for your program's standard input and

SEE ALSO         top

       The full documentation for GDB is maintained as a Texinfo manual.
       If the "info" and "gdb" programs and GDB's Texinfo documentation
       are properly installed at your site, the command

               info gdb

       should give you access to the complete manual.

       Using GDB: A Guide to the GNU Source-Level Debugger, Richard M.
       Stallman and Roland H. Pesch, July 1991.

COPYRIGHT         top

       Copyright (c) 1988-2023 Free Software Foundation, Inc.

       Permission is granted to copy, distribute and/or modify this
       document under the terms of the GNU Free Documentation License,
       Version 1.3 or any later version published by the Free Software
       Foundation; with the Invariant Sections being "Free Software" and
       "Free Software Needs Free Documentation", with the Front-Cover
       Texts being "A GNU Manual," and with the Back-Cover Texts as in
       (a) below.

       (a) The FSF's Back-Cover Text is: "You are free to copy and
       modify this GNU Manual.  Buying copies from GNU Press supports
       the FSF in developing GNU and promoting software freedom."

COLOPHON         top

       This page is part of the gdb (GNU debugger) project.  Information
       about the project can be found at 
       ⟨⟩.  If you have a bug report for
       this manual page, see ⟨⟩.
       This page was obtained from the tarball gdb-14.2.tar.gz fetched
       from ⟨⟩ on 2024-06-14.  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to

gdb-14.2                       2024-03-03                         GDB(1)

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