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 gdb(1)                           GNU Tools                           gdb(1)
 GNU Tools                                                         GNU Tools

                                  22may2002



 NAME
      gdb - The GNU Debugger

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

 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++,  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:




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 GNU Tools                                                         GNU Tools

                                  22may2002



      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



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 gdb(1)                           GNU Tools                           gdb(1)
 GNU Tools                                                         GNU Tools

                                  22may2002



      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.


      -help

      -h   List all options, with brief explanations.


      -symbols=file

      -s file
            Read symbol table from file file.


      -write
           Enable writing into executable and core files.


      -exec=file

      -e file
             Use  file  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 file and use it  as  the  executable
           file.


      -core=file

      -c file



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 gdb(1)                           GNU Tools                           gdb(1)
 GNU Tools                                                         GNU Tools

                                  22may2002



            Use file file as a core dump to examine.


      -command=file

      -x file
            Execute GDB commands from file file.


      -ex command
            Execute given GDB command.


      -directory=directory

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

      -nh  Do not execute commands from ~/.gdbinit.


      -nx

      -n   Do not execute commands from any `.gdbinit' initialization files.



      -quiet

      -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.




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 gdb(1)                           GNU Tools                           gdb(1)
 GNU Tools                                                         GNU Tools

                                  22may2002



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


      -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 ` 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.


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


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

 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.

 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.



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 gdb(1)                           GNU Tools                           gdb(1)
 GNU Tools                                                         GNU Tools

                                  22may2002



      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.















































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