FreeBSD Man Pages

gdb(1)

NAME

       gdb - The GNU Debugger

SYNOPSIS

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

	  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 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
       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:

       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-
	      point).

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

       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.

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.

       -exec=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.

       -directory=directory

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

       -nx

       -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.

       -quiet

       -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.

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

	      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.

       -kernel

       -k     Use  gdb	in  kernel  debugging  mode.  The  prompt  is  set  to
	      ``(kgdb)''.

       -wcore This option may only be used  in	kernel	debugging  mode  while
	      debugging  a  ``live''  kernel and makes the corefile (/dev/mem)
	      writable.

       -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

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

COPYING

       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 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.

GNU Tools			   4nov1991				gdb(1)

SPONSORED LINKS