path: root/gdb/gdb.1

.\" Copyright 1991, 1999 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 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.