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 User-defined commands
 =====================
 
    A "user-defined command" is a sequence of GDB commands to which you
 assign a new name as a command.  This is done with the `define'
 command.  User commands may accept up to 10 arguments separated by
 whitespace.  Arguments are accessed within the user command via
 $ARG0...$ARG9.  A trivial example:
 
      define adder
        print $arg0 + $arg1 + $arg2
 
 To execute the command use:
 
      adder 1 2 3
 
 This defines the command `adder', which prints the sum of its three
 arguments.  Note the arguments are text substitutions, so they may
 reference variables, use complex expressions, or even perform inferior
 functions calls.
 
 `define COMMANDNAME'
      Define a command named COMMANDNAME.  If there is already a command
      by that name, you are asked to confirm that you want to redefine
      it.
 
      The definition of the command is made up of other GDB command
      lines, which are given following the `define' command.  The end of
      these commands is marked by a line containing `end'.
 
 `if'
      Takes a single argument, which is an expression to evaluate.  It
      is followed by a series of commands that are executed only if the
      expression is true (nonzero).  There can then optionally be a line
      `else', followed by a series of commands that are only executed if
      the expression was false.  The end of the list is marked by a line
      containing `end'.
 
 `while'
      The syntax is similar to `if': the command takes a single argument,
      which is an expression to evaluate, and must be followed by the
      commands to execute, one per line, terminated by an `end'.  The
      commands are executed repeatedly as long as the expression
      evaluates to true.
 
 `document COMMANDNAME'
      Document the user-defined command COMMANDNAME, so that it can be
      accessed by `help'.  The command COMMANDNAME must already be
      defined.  This command reads lines of documentation just as
      `define' reads the lines of the command definition, ending with
      `end'.  After the `document' command is finished, `help' on command
      COMMANDNAME displays the documentation you have written.
 
      You may use the `document' command again to change the
      documentation of a command.  Redefining the command with `define'
      does not change the documentation.
 
 `help user-defined'
      List all user-defined commands, with the first line of the
      documentation (if any) for each.
 
 `show user'
 `show user COMMANDNAME'
      Display the GDB commands used to define COMMANDNAME (but not its
      documentation).  If no COMMANDNAME is given, display the
      definitions for all user-defined commands.
 
    When user-defined commands are executed, the commands of the
 definition are not printed.  An error in any command stops execution of
 the user-defined command.
 
    If used interactively, commands that would ask for confirmation
 proceed without asking when used inside a user-defined command.  Many
 GDB commands that normally print messages to say what they are doing
 omit the messages when used in a user-defined command.
 

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