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Updated: July 2017

gdb (1)


gdb - The GNU Debugger


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]]


gdb(1)                             GNU Tools                            gdb(1)

       gdb - The GNU Debugger

       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]]

       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

          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 cor-
              recting 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 com-
       mands 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

       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

       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 break-

       next   Execute next program line (after stopping); step over any  func-
              tion 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  func-
              tion 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.

       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


       -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  appropri-
              ate,  and  for  examining  pure  data in conjunction with a core

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


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


       -x file
               Execute GDB commands from file file.

       -ex command
               Execute given GDB command.


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

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


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


       -q     ``Quiet''.  Do not print the  introductory  and  copyright  mes-
              sages.  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 inhib-
              ited).  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  exam-
              ple  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.

                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  dis-
              played  (which includes each time the program stops).  This rec-
              ognizable 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.

       See attributes(5) for descriptions of the following attributes:

       |Availability   | developer/debug/gdb |
       |Stability      | Uncommitted         |
       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. Stall-
       man and Roland H. Pesch, July 1991.

       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  per-
       mission notice identical to this one.

       Permission  is granted to copy and distribute translations of this man-
       ual into another language, under the above conditions for modified ver-
       sions,  except  that this permission notice may be included in transla-
       tions approved by the Free Software Foundation instead of in the origi-
       nal English.

       This     software     was    built    from    source    available    at
       https://java.net/projects/solaris-userland.   The  original   community
       source was downloaded from  http://ftp.gnu.org/gnu/gdb/gdb-7.6.tar.gz

       Further information about this software can be found on the open source
       community website at http://www.gnu.org/software/gdb/.

GNU Tools                          22may2002                            gdb(1)