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 GDB(1)                           gdb-7.9.1                           GDB(1)
 GNU Development Tools                                 GNU Development Tools

                                 2015-05-14



 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] [-p procID]
          [-x cmds] [-d dir] [prog|prog procID|prog core]

 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@t{++}, Fortran and
      Modula-2.

      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:




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 GDB(1)                           gdb-7.9.1                           GDB(1)
 GNU Development Tools                                 GNU Development Tools

                                 2015-05-14



              gdb program 1234
              gdb -p 1234

      would attach GDB to process 1234 (unless you also have a file named
      1234; GDB does check for a core file first).  With option -p you can
      omit the program filename.

      Here are some of the most frequently needed GDB commands:

      break [file:]functiop
          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.




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 GDB(1)                           gdb-7.9.1                           GDB(1)
 GNU Development Tools                                 GNU Development Tools

                                 2015-05-14



 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
          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.




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 GDB(1)                           gdb-7.9.1                           GDB(1)
 GNU Development Tools                                 GNU Development Tools

                                 2015-05-14



      -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.

      -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 \032 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 \032 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



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 GDB(1)                           gdb-7.9.1                           GDB(1)
 GNU Development Tools                                 GNU Development Tools

                                 2015-05-14



              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.

 COPYRIGHT
      Copyright (c) 1988-2015 Free Software Foundation, Inc.

      Permission is granted to copy, distribute and/or modify this document
      under the terms of the GNU Free Documentation License, Version 1.3 or
      any later version published by the Free Software Foundation; with the
      Invariant Sections being "Free Software" and "Free Software Needs Free
      Documentation", with the Front-Cover Texts being "A GNU Manual," and
      with the Back-Cover Texts as in (a) below.

      (a) The FSF's Back-Cover Text is: "You are free to copy and modify
      this GNU Manual.  Buying copies from GNU Press supports the FSF in
      developing GNU and promoting software freedom."
































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