erl_error (stdlib v3.15.2)

This module provides functions for pretty-printing errors and exceptions. It is used by both the shell and by proc_lib to print exceptions.

It is possible for the module raising an error to provide additional information by calling error/3 with extra error information. More details about this mechanism is described in EEP-54.

Callback Functions

The following functions are to be exported from an Error Info handler.

Link to this section Summary

Types

-type column() :: term().

Start column number. Default is 1.

-type format_fun() :: term().

A fun used to format function arguments for BIF and function calls. By default the following fun will be used

-type format_options() :: term().

A map with formatting options.

-type stack_trim_fun() :: term().

A fun used to trim the end of the stacktrace. It is called with module, function, and arity from an entry from the stacktrace. The fun is to return true if the entry should be trimmed, and false otherwise. The default value is

Functions

format_exception/3

Format the error reason and stack back-trace caught using try ... catch in the same style as the shell formats them.

format_exception/4

Link to this section Types

-type column() :: term().

Specs

column() :: pos_integer().

Start column number. Default is 1.

-type format_fun() :: term().

Specs

format_fun() :: fun((term(), column()) -> iolist()).

A fun used to format function arguments for BIF and function calls. By default the following fun will be used:

fun(Term, I) -> io_lib:print(Term, I, 80, 30) end

-type format_options() :: term().

Specs

format_options() ::
    #{column => column(), stack_trim_fun => stack_trim_fun(), format_fun => format_fun()}.

A map with formatting options.

-type stack_trim_fun() :: term().

Specs

stack_trim_fun() :: fun((module(), atom(), arity()) -> boolean()).

fun(_, _, _) -> false end

Link to this section Functions

format_exception/3

(since OTP 24.0)

Specs

format_exception(Class, Reason, StackTrace) -> unicode:chardata()
                    when
                        Class :: error | exit | throw,
                        Reason :: term(),
                        StackTrace :: erlang:stacktrace().

Format the error reason and stack back-trace caught using try ... catch in the same style as the shell formats them.

Example:

try
    do_something()
catch
    C:R:Stk ->
        Message = erl_error:format_exception(C, R, Stk),
        io:format(LogFile, "~ts\n", [Message])
end

If error_info is provided with the exception, format_exception will use that information to provide additional information about the exception.

Example:

try
  erlang:raise(badarg,[],[{error_info,#{}}])
catch
    C:R:Stk ->
        Message = erl_error:format_exception(C, R, Stk),
        io:format(LogFile, "~ts\n", [Message])
end

See erlang:error/3 for details on how to raise an exception with error_info included.

format_exception/4

(since OTP 24.0)

Specs

format_exception(Class, Reason, StackTrace, Options) -> unicode:chardata()
                    when
                        Class :: error | exit | throw,
                        Reason :: term(),
                        StackTrace :: erlang:stacktrace(),
                        Options :: format_options().