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NAME

       gdb - The GNU Debugger

SYNOPSIS

       gdb    [-help] [-nx] [-q] [-batch] [-cd=dir] [-f] [-b bps] [-tty=dev]
              [-s symfile] [-e prog] [-se prog] [-c core] [-x cmds] [-d dir]
              [prog [core|procID]]

       gdb    [options] --args prog [arguments]

       gdbtui [options]

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:

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

          o   Make your program stop on specified conditions.

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

          o   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++, and Modula-2.
       Fortran support will be added when a GNU Fortran compiler is ready.

       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.  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,  if  you
       want to debug a running process:

       gdb program 1234

       would  attach  GDB  to  process 1234 (unless you also have a file named
       `1234'; GDB does check for a core file first).

       Here are some of the most frequently needed GDB commands:

       break [file:]function
               Set a breakpoint at function (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 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 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 `+' rather than `-',  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 `-x' option is
       used.

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

       -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.

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

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

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

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

       -f, -fullname
              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 ` 32' 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 ` 32' characters as a signal to display the source  code
              for the frame.

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

       -n, -nx
              Do  not  execute  commands  from  any  `.gdbinit' initialization
              files.  Normally, the commands in these files are executed after
              all the command options and arguments have been processed.

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

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

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

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

       --args Pass arguments after the program name to the program when it  is
              run.

       -tui   Run GDB using a text (console) user interface.

       -write Enable writing into executable and core files.

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

SEE ALSO

       `gdb'  entry  in  info;  Using  GDB:  A  Guide  to the GNU Source-Level
       Debugger, Richard M. Stallman and Roland H. Pesch, July 1991.

COPYING

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

       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.

       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.

       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.