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.\" Copyright (C) 1991, 1999, 2010 Free Software Foundation, Inc.

.\" See section COPYING for conditions for redistribution

.\" $Id: gdb.1,v 1.4 1999/01/05 00:50:50 jsm Exp $

.TH gdb 1 "22may2002" "GNU Tools" "GNU Tools"

.SH NAME

gdb \- The GNU Debugger

.SH SYNOPSIS

.na

.TP

.B gdb

.RB "[\|" \-help "\|]"

.RB "[\|" \-nx "\|]"

.RB "[\|" \-q "\|]"

.RB "[\|" \-batch "\|]"

.RB "[\|" \-cd=\c

.I dir\c

\|]

.RB "[\|" \-f "\|]"

.RB "[\|" "\-b\ "\c

.IR bps "\|]"

.RB "[\|" "\-tty="\c

.IR dev "\|]"

.RB "[\|" "\-s "\c

.I symfile\c

\&\|]

.RB "[\|" "\-e "\c

.I prog\c

\&\|]

.RB "[\|" "\-se "\c

.I prog\c

\&\|]

.RB "[\|" "\-c "\c

.I core\c

\&\|]

.RB "[\|" "\-x "\c

.I cmds\c

\&\|]

.RB "[\|" "\-d "\c

.I dir\c

\&\|]

.RB "[\|" \c

.I prog\c

.RB "[\|" \c

.IR core \||\| procID\c

\&\|]\&\|]

.ad b

.SH 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\(em\&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:

.TP

\ \ \ \(bu

Start your program, specifying anything that might affect its behavior.

.TP

\ \ \ \(bu

Make your program stop on specified conditions.

.TP

\ \ \ \(bu

Examine what has happened, when your program has stopped.

.TP

\ \ \ \(bu

Change things in your program, so you can experiment with correcting the

effects of one bug and go on to learn about another.

.PP

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

Fortran support will be added when a GNU Fortran compiler is ready.

GDB is invoked with the shell command \c

.B gdb\c

\&.  Once started, it reads

commands from the terminal until you tell it to exit with the GDB

command \c

.B quit\c

\&.  You can get online help from \c

.B gdb\c

\& itself

by using the command \c

.B help\c

\&.

You can run \c

.B gdb\c

\& 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:

.sp

.br

gdb\ program

.br

.sp

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

.sp

.br

gdb\ program\ core

.br

.sp

You can, instead, specify a process ID as a second argument, if you want

to debug a running process:

.sp

.br

gdb\ program\ 1234

.br

.sp

would attach GDB to process \c

.B 1234\c

\& (unless you also have a file

named `\|\c

.B 1234\c

\&\|'; GDB does check for a core file first).

Here are some of the most frequently needed GDB commands:

.TP

.B break \fR[\|\fIfile\fB:\fR\|]\fIfunction

\&

Set a breakpoint at \c

.I function\c

\& (in \c

.I file\c

\&).

.TP

.B run \fR[\|\fIarglist\fR\|]

Start your program (with \c

.I arglist\c

\&, if specified).

.TP

.B bt

Backtrace: display the program stack.

.TP

.BI print " expr"\c

\&

Display the value of an expression.

.TP

.B c

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

.TP

.B next

Execute next program line (after stopping); step \c

.I over\c

\& any

function calls in the line.

.TP

.B edit \fR[\|\fIfile\fB:\fR\|]\fIfunction

look at the program line where it is presently stopped.

.TP

.B list \fR[\|\fIfile\fB:\fR\|]\fIfunction

type the text of the program in the vicinity of where it is presently stopped.

.TP

.B step

Execute next program line (after stopping); step \c

.I into\c

\& any

function calls in the line.

.TP

.B help \fR[\|\fIname\fR\|]

Show information about GDB command \c

.I name\c

\&, or general information

about using GDB.

.TP

.B quit

Exit from GDB.

.PP

For full details on GDB, see \c

.I

Using GDB: A Guide to the GNU Source-Level Debugger\c

\&, by Richard M. Stallman and Roland H. Pesch.  The same text is available online

as the \c

.B gdb\c

\& entry in the \c

.B info\c

\& program.

.SH 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 `\|\c

.B \-se\c

\&\|' option, and the

second, if any, is equivalent to a `\|\c

.B \-c\c

\&\|' 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 `\|\c

.B +\c

\&\|' rather than `\|\c

.B \-\c

\&\|', though we illustrate the

more usual convention.)

All the options and command line arguments you give are processed

in sequential order.  The order makes a difference when the

`\|\c

.B \-x\c

\&\|' option is used.

.TP

.B \-help

.TP

.B \-h

List all options, with brief explanations.

.TP

.BI "\-symbols=" "file"\c

.TP

.BI "\-s " "file"\c

\&

Read symbol table from file \c

.I file\c

\&.

.TP

.B \-write

Enable writing into executable and core files.

.TP

.BI "\-exec=" "file"\c

.TP

.BI "\-e " "file"\c

\&

Use file \c

.I file\c

\& as the executable file to execute when

appropriate, and for examining pure data in conjunction with a core

dump.

.TP

.BI "\-se=" "file"\c

\&

Read symbol table from file \c

.I file\c

\& and use it as the executable

file.

.TP

.BI "\-core=" "file"\c

.TP

.BI "\-c " "file"\c

\&

Use file \c

.I file\c

\& as a core dump to examine.

.TP

.BI "\-command=" "file"\c

.TP

.BI "\-x " "file"\c

\&

Execute GDB commands from file \c

.I file\c

\&.

.TP

.BI "\-directory=" "directory"\c

.TP

.BI "\-d " "directory"\c

\&

Add \c

.I directory\c

\& to the path to search for source files.

.PP

.TP

.B \-nx

.TP

.B \-n

Do not execute commands from any `\|\c

.B .gdbinit\c

\&\|' initialization files.

Normally, the commands in these files are executed after all the

command options and arguments have been processed.

.TP

.B \-quiet

.TP

.B \-q

``Quiet''.  Do not print the introductory and copyright messages.  These

messages are also suppressed in batch mode.

.TP

.B \-batch

Run in batch mode.  Exit with status \c

.B 0\c

\& after processing all the command

files specified with `\|\c

.B \-x\c

\&\|' (and `\|\c

.B .gdbinit\c

\&\|', 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

.sp

.br

Program\ exited\ normally.

.br

.sp

(which is ordinarily issued whenever a program running under GDB control

terminates) is not issued when running in batch mode.

.TP

.BI "\-cd=" "directory"\c

\&

Run GDB using \c

.I directory\c

\& as its working directory,

instead of the current directory.

.TP

.B \-fullname

.TP

.B \-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 `\|\c

.B \032\c

\&\|' 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 `\|\c

.B \032\c

\&\|' characters as

a signal to display the source code for the frame.

.TP

.BI "\-b " "bps"\c

\&

Set the line speed (baud rate or bits per second) of any serial

interface used by GDB for remote debugging.

.TP

.BI "\-tty=" "device"\c

\&

Run using \c

.I device\c

\& for your program's standard input and output.

.PP

.SH "SEE ALSO"

.RB "`\|" gdb "\|'"

entry in

.B info\c

\&;

.I

Using GDB: A Guide to the GNU Source-Level Debugger\c

, Richard M. Stallman and Roland H. Pesch, July 1991.

.SH COPYING

Copyright (c) 1991, 2010 Free Software Foundation, Inc.

.PP

Permission is granted to make and distribute verbatim copies of

this manual provided the copyright notice and this permission notice

are preserved on all copies.

.PP

Permission is granted to copy and distribute modified versions of this

manual under the conditions for verbatim copying, provided that the

entire resulting derived work is distributed under the terms of a

permission notice identical to this one.

.PP

Permission is granted to copy and distribute translations of this

manual into another language, under the above conditions for modified

versions, except that this permission notice may be included in

translations approved by the Free Software Foundation instead of in

the original English.