Node:Help, Previous:Completion, Up:Commands

### Getting help

You can always ask GDB itself for information on its commands, using the command `help`.

`help`
`h`
  You can use `help` (abbreviated `h`) with no arguments to display a short list of named classes of commands:

                (gdb) help
                List of classes of commands:

                aliases -- Aliases of other commands
                breakpoints -- Making program stop at certain points
                data -- Examining data
                files -- Specifying and examining files
                internals -- Maintenance commands
                obscure -- Obscure features
                running -- Running the program
                stack -- Examining the stack
                status -- Status inquiries
                support -- Support facilities
                tracepoints -- Tracing of program execution without

                               stopping the program
                user-defined -- User-defined commands

                Type "help" followed by a class name for a list of
                commands in that class.
                Type "help" followed by command name for full
                documentation.
                Command name abbreviations are allowed if unambiguous.
                (gdb)

`help` class``
  Using one of the general help classes as an argument, you can get a list of the individual commands in that class. For example, here is the help display for the class `status`:

                (gdb) help status
                Status inquiries.

                List of commands:

                info -- Generic command for showing things
                 about the program being debugged
                show -- Generic command for showing things
                 about the debugger

                Type "help" followed by command name for full
                documentation.
                Command name abbreviations are allowed if unambiguous.
                (gdb)

`help` command``
  With a command name as `help` argument, GDB displays a short paragraph on how to use that command.
`apropos` args``
  The `apropos` args`` command searches through all of the GDB commands, and their documentation, for the regular expression specified in args. It prints out all matches found. For example:

                apropos reload

  results in:

                set symbol-reloading -- Set dynamic symbol table reloading
                                                 multiple times in one run
                show symbol-reloading -- Show dynamic symbol table reloading
                                                 multiple times in one run

`complete` args``
  The `complete` args`` command lists all the possible completions for the beginning of a command. Use args to specify the beginning of the command you want completed. For example:

                complete i

  results in:

                if
                ignore
                info
                inspect

  This is intended for use by GNU Emacs.

In addition to `help`, you can use the GDB commands `info` and `show` to inquire about the state of your program, or the state of GDB itself. Each command supports many topics of inquiry; this manual introduces each of them in the appropriate context. The listings under `info` and under `show` in the Index point to all the sub-commands. See Index.

`info`
  This command (abbreviated `i`) is for describing the state of your program. For example, you can list the arguments given to your program with `info args`, list the registers currently in use with `info registers`, or list the breakpoints you have set with `info breakpoints`. You can get a complete list of the `info` sub-commands with `help info`.
`set`
  You can assign the result of an expression to an environment variable with `set`. For example, you can set the GDB prompt to a $-sign with `set prompt $`.
`show`
  In contrast to `info`, `show` is for describing the state of GDB itself. You can change most of the things you can `show`, by using the related command `set`; for example, you can control what number system is used for displays with `set radix`, or simply inquire which is currently in use with `show radix`.

  To display all the settable parameters and their current values, you can use `show` with no arguments; you may also use `info set`. Both commands produce the same display.

Here are three miscellaneous `show` subcommands, all of which are exceptional in lacking corresponding `set` commands:

`show version`
  Show what version of GDB is running. You should include this information in GDB bug-reports. If multiple versions of GDB are in use at your site, you may need to determine which version of GDB you are running; as GDB evolves, new commands are introduced, and old ones may wither away. Also, many system vendors ship variant versions of GDB, and there are variant versions of GDB in GNU/Linux distributions as well. The version number is the same as the one announced when you start GDB.
`show copying`
  Display information about permission for copying GDB.
`show warranty`
  Display the GNU "NO WARRANTY" statement, or a warranty, if your version of GDB comes with one.