Reference Manual

Version 3.4

Table of Contents




Module Summary

The Erlang code linter.


This module is used to check Erlang code for illegal syntax and other bugs. It also warns against coding practices that are not recommended.

The errors detected include:

  • Redefined and undefined functions
  • Unbound and unsafe variables
  • Illegal record use

The warnings detected include:

  • Unused functions and imports
  • Unused variables
  • Variables imported into matches
  • Variables exported from if/case/receive
  • Variables shadowed in funs and list comprehensions

Some of the warnings are optional, and can be turned on by specifying the appropriate option, described below.

The functions in this module are invoked automatically by the Erlang compiler. There is no reason to invoke these functions separately unless you have written your own Erlang compiler.

Data Types


format_error(ErrorDescriptor) -> io_lib:chars()


ErrorDescriptor = error_description()

Takes an ErrorDescriptor and returns a string that describes the error or warning. This function is usually called implicitly when processing an ErrorInfo structure (see section Error Information).

is_guard_test(Expr) -> boolean()

Tests if Expr is a legal guard test. Expr is an Erlang term representing the abstract form for the expression. erl_parse:parse_exprs(Tokens) can be used to generate a list of Expr.

module(AbsForms) -> {ok, Warnings} | {error, Errors, Warnings}
module(AbsForms, FileName) ->
          {ok, Warnings} | {error, Errors, Warnings}
module(AbsForms, FileName, CompileOptions) ->
          {ok, Warnings} | {error, Errors, Warnings}


FileName = atom() | string()
CompileOptions = [compile:option()]
Warnings = [{file:filename(), [ErrorInfo]}]
Errors = [{FileName2 :: file:filename(), [ErrorInfo]}]
ErrorInfo = error_info()

Checks all the forms in a module for errors. It returns:


There are no errors in the module.


There are errors in the module.

As this module is of interest only to the maintainers of the compiler, and to avoid the same description in two places, the elements of Options that control the warnings are only described in the compile(3) module.

AbsForms of a module, which comes from a file that is read through epp, the Erlang preprocessor, can come from many files. This means that any references to errors must include the filename, see the epp(3) module or parser (see the erl_parse(3) module). The returned errors and warnings have the following format:


The errors and warnings are listed in the order in which they are encountered in the forms. The errors from one file can therefore be split into different entries in the list of errors.

Error Information

ErrorInfo is the standard ErrorInfo structure that is returned from all I/O modules. The format is as follows:

{ErrorLine, Module, ErrorDescriptor}

A string describing the error is obtained with the following call:


See Also