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gdb(1)                                            GNU Tools                                           gdb(1)

       gdb - The GNU Debugger

       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]]

       The purpose of a debugger such as GDB is to allow you to see what is going on ``inside'' another pro-gram program
       gram 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  argu-ment argument
       ment 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 pro-gram. program.

       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.


       -h     List all options, with brief explanations.


       -s file
               Read symbol table from file file.

       -write Enable writing into executable and core files.


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

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


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


       -x file
               Execute GDB commands from file file.


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


       -n     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.


       -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  exe-cuting executing
              cuting 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 pro-gram program
              gram 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.

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


       -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.

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

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

       Further   documentation   is   available   in   /Developer/Documentation/DocSets/ /Developer/Documentation/DocSets/

       Copyright (c) 1991 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.

GNU Tools                                         22may2002                                           gdb(1)

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