int(3)

MODULE
int - Interpreter Interface.

DESCRIPTION

The Erlang interpreter provides mechanisms for breakpoints and stepwise execution of code. It is mainly intended to be used by the Debugger, see Debugger User's Guide and debugger(3).

From the shell, it is possible to:

    *   Specify which modules should be interpreted.

    *   Specify breakpoints.

    *   Monitor the current status of all processes executing code in interpreted modules, also processes at other Erlang nodes.

By attaching to a process executing interpreted code, it is possible to examine variable bindings and order stepwise execution. This is done by sending and receiving information to/from the process via a third process, called the meta process. It is possible, but not recommended, to implement your own attached process. See int.erl for available functions and dbg_ui_trace.erl for possible messages.

Breakpoints

Breakpoints are specified on a line basis. When a process executing code in an interpreted module reaches a breakpoint, it will stop. This means that that a breakpoint must be set at an executable line, i.e. a line of code containing an executable expression.

A breakpoint have a status, a trigger action and may have a condition associated with it. The status is either active or inactive. An inactive breakpoint is ignored. When a breakpoint is reached, the trigger action specifies if the breakpoint should continue to be active (enable), if it should become inactive (disable), or if it should be removed (delete). A condition is a tuple {Module, Name}. When the breakpoint is reached, Module:Name(Bindings) is called. If this evaluates to true, execution will stop. If this evaluates to false, the breakpoint is ignored. Bindings contains the current variable bindings, use get_binding to retrieve the value for a given variable.

By default, a breakpoint is active, has trigger action enable and has no condition associated with it. For more detailed information about breakpoints, refer to Debugger User's Guide.

EXPORTS

i(AbsModule) -> {module,Module} | error
ni(AbsModule) -> {module,Module} | error

    Types
        AbsModule = Module | File | [Module | File]
         Module = atom()
         File = string()
        Options = term()

    Interprets the specified module. i/1, 2 interprets the module only at the current node. ni/1, 2 interprets the module at all known nodes.

    A module may be given by its module name (atom) or by its file name. If given by its module name, the object code Module.beam is searched for in the current path. The source code Module.erl is searched for first in the same directory as the object code, then in a src directory next to it.

    If given by its file name, the file name may include a path and the .erl extension may be omitted. The object code Module.beam is searched for first in the same directory as the source code, then in an ebin directory next to it, and then in the current path.

  Note:

The interpreter needs both the source code and the object code, and the object code must include debug information. That is, only modules compiled with the option debug_info set can be interpreted.

n(AbsModule) -> ok
nn(AbsModule) -> ok

    Types
        AbsModule = Module | File | [Module | File]
         Module = atom()
         File = string()

    Stops interpreting the specified module. n/1 stops interpreting the node only at the current node. nn/1 stops interpreting the module at all known nodes.

    As for i/1 and ni/1, a module may be given by either its module name or its file name.

interpreted() -> [Module]

    Types
        Module = atom()

    Returns a list with all interpreted modules.

file(Module) -> File | {error,not_loaded}

    Types
        Module = atom()
        File = string()

    Returns the source code file name File for an interpreted module Module.

interpretable(AbsModule) -> true | {error,Reason}

    Types
        AbsModule = Module | File
         Module = atom()
         File = string()
        Reason = no_src | no_beam | no_debug_info | badarg

    Checks if a module is possible to interpret. The module can be given by its module name Module or its file name File.

    The function returns true if both source code and object code for the module is found, and the module has been compiled with the option debug_info set.

    The function returns {error, Reason} where Reason is no_src if no source code is found, no_beam if no object code is found, no_debug_info if the module has not been compiled with the option debug_info set, or badarg if AbsModule does not exist.

auto_attach() -> false | {Flags,Function}
auto_attach(false)
auto_attach(Flags, Function)

    Types
        Flags = [init | break | exit]
        Function = {Module, Name, Args}
         Module = Name = atom()
         Args = [term()]

    Get and set when and how to automatically attach to a process executing code in interpreted modules. false means never attach, this is the default. Otherwise automatic attach is defined by a list of flags and a function. The following flags may be specified:

        *   init - attach when a process for the very first time calls an interpreted function.

        *   break - attach whenever a process reaches a breakpoint.

        *   exit - attach when a process terminates.

    When the specified event occurs, the function Function will be called as:
    spawn(Module, Name, [Pid | Args])

    The resulting process can attach to, i.e. send commands to and receive messages from, the interpreted process, see above.

stack_trace() -> Flag
stack_trace(Flag)

    Types
        Flag = all | no_tail | false

    Get and set how to save call frames in the stack. This makes it possible to inspect the call chain of a process.

        *   all - save all call frames. This is the default.

        *   no_tail - save all call frames, except for tail recursive calls. This option consumes less memory and may be necessary to use for processes with long lifetimes and many tail recursive calls.

        *   false - do not save call frames.

break(Module, Line) -> ok | {error,break_exists}

    Types
        Module = atom()
        Line = integer()

    Creates a breakpoint at Line in Module.

delete_break(Module, Line) -> ok

    Types
        Module = atom()
        Line = integer()

    Deletes the breakpoint located at Line in Module.

break_in(Module, Name, Arity) -> ok | {error,function_not_found}

    Types
        Module = Name = atom()
        Function = atom()
        Arity = integer()

    Create a breakpoint at the first line of every clause of the Module:Function/Arity function.

del_break_in(Module, Name, Arity) -> ok | {error,function_not_found}

    Types
        Module = Name = atom()
        Arity = integer()

    Delete the breakpoints at the first line of every clause of the Module:Function/Arity function.

no_break() -> ok
no_break(Module) -> ok

    Deletes all breakpoints, or all breakpoints in Module.

disable_break(Module, Line) -> ok

    Types
        Module = atom()
        Line = integer()

    Makes the breakpoint at Line in Module inactive.

enable_break(Module, Line) -> ok

    Types
        Module = atom()
        Line = integer()

    Makes the breakpoint at Line in Module active.

action_at_break(Module, Line, Action) -> ok

    Types
        Module = atom()
        Line = integer()
        Action = enable | disable | delete

    Set the trigger action of the breakpoint at Line in Module to Action.

test_at_break(Module, Line, Function) -> ok

    Types
        Module = atom()
        Line = integer()
        Function = {Module, Name}
        Module = Name = atom()

    Set the condition of the breakpoint at Line in Module to Function.

get_binding(Var, Bindings) -> {value,Value} | unbound

    Types
        Var = atom()
        Bindings = term()
        Value = term()

    Retrieve the binding of Variable. This function is intended to be used by a breakpoint condition function.

all_breaks() -> [Break]
all_breaks(Module) -> [Break]

    Types
        Break = {Point, Options}
         Point = {Module, Line}
          Module = atom()
          Line = int()
         Options = [Status, Trigger, null, Cond|]
          Status = active | inactive
          Trigger = enable | disable | delete
          Cond = null | Function
           Function = {Module, Name}
            Name = atom()

    Gets all breakpoints, or all breakpoints in Module.

snapshot() -> [Snapshot]

    Types
        Snapshot = {Pid, Function, Status, Info}
         Pid = pid()
         Function = {Module, Name, Args}
          Module = Name = atom()
          Args = [term()]
         Status = idle | running | waiting | break | exit | no_conn
         Info = {} | {Module, Line} | ExitReason
          Line = integer()
          ExitReason = term()

    Gets information about all processes executing interpreted code.

        *   Pid - process identifier.

        *   Function - first interpreted function called by the process.

        *   Status - current status of the process.

        *   Info - additional information.

    Status is one of:

        *   idle - the process is no longer executing interpreted code. Info={}.

        *   running - the process is running. Info={}.

        *   waiting - the process is waiting at a receive. Info={}.

        *   break - process execution has been stopped, normally at a breakpoint. Info={Module, Line}.

        *   exit - the process has terminated. Info=ExitReason.

        *   no_conn - the connection is down to the node where the process is running. Info={}.

clear() -> ok

    Clears information about processes executing interpreted code by removing all information about terminated processes.

continue(Pid) -> ok | {error,not_interpreted}
continue(X,Y,Z) -> ok | {error,not_interpreted}

    Types
        Pid = pid()
        X = Y = Z = integer()

    Resume process execution for Pid, or for c:pid(X, Y, Z).

AUTHOR
Gunilla Arendt - support@erlang.ericsson.se