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NetBSD 6.1.5 - man page for gdb (netbsd section 1)

gdb(1)					    GNU Tools					   gdb(1)

NAME
       gdb - The GNU Debugger

SYNOPSIS
       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]]

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 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 ter-
       minal 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  run-
       ning 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 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 examin-
	      ing 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.

       -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 messages.   These  messages
	      are also suppressed in batch mode.

       -batch Run in batch mode.  Exit with status 0 after processing all the command files spec-
	      ified 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  termi-
	      nates) is not issued when running in batch mode.

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

       -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 recog-
	      nizable  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
       `gdb'  entry  in  info;	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  dis-
       tributed under the terms of a permission notice identical to this one.

       Permission is granted to copy and distribute translations of this manual into another lan-
       guage, 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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