GDB(1)			     GNU Development Tools			GDB(1)


NAME
       gdb - The GNU Debugger

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

DESCRIPTION
       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
	   behavior.

       •   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 another.

       You can use GDB to debug programs written in C, C++, Fortran and
       Modula-2.

       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
	   breakpoint).

       next
	   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.

       step
	   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.

       quit
       exit
	   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
       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"
       "-option=value"
       "-option value"
       "--o=value"
       "--o 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.

       --help
       -h  List all options, with brief explanations.

       --symbols=file
       -s file
	   Read symbol table from file.

       --write
	   Enable writing into executable and core files.

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

       --se=file
	   Read symbol table from file and use it as the executable file.

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

       --command=file
       -x file
	   Execute GDB commands from file.

       --eval-command=command
       -ex command
	   Execute given GDB command.

       --init-eval-command=command
       -iex
	   Execute GDB command before loading the inferior.

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

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

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

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

       --batch
	   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 mode.

       --batch-silent
	   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.

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

       --tui
	   Open the terminal user interface.

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

       --readnever
	   Do not read symbol files.

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

       --configuration
	   Print details about GDB configuration and then exit.

       --version
	   Print version information and then exit.

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

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

       --fullname
       -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.

       --tty=device
	   Run using device for your program's standard input and output.

ENVIRONMENT
SEE ALSO
       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
       Copyright (c) 1988-2024 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."

gdb-16.3			  2025-04-20				GDB(1)