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Interface to the Erlang code server process.
This module contains the interface to the Erlang code server, which deals with the loading of compiled code into a running Erlang runtime system.
The runtime system can be started in interactive or embedded mode. Which one
is decided by the command-line flag -mode
:
% erl -mode embedded
The modes are as follows:
In interactive mode, which is default, only the modules needed by the runtime system are loaded during system startup. Other code is dynamically loaded when first referenced. When a call to a function in a certain module is made, and that module is not loaded, the code server searches for and tries to load that module.
In embedded mode, modules are not auto-loaded. Trying to use a module that has not been loaded results in an error. This mode is recommended when the boot script loads all modules, as it is typically done in OTP releases. (Code can still be loaded later by explicitly ordering the code server to do so).
To prevent accidentally reloading of modules affecting the Erlang runtime
system, directories kernel
, stdlib
, and compiler
are considered sticky.
This means that the system issues a warning and rejects the request if a user
tries to reload a module residing in any of them. The feature can be disabled by
using command-line flag -nostick
.
Code Path
In interactive mode, the code server maintains a code path, consisting of a list of directories, which it searches sequentially when trying to load a module.
Initially, the code path consists of the current working directory and all
Erlang object code directories under library directory $OTPROOT/lib
, where
$OTPROOT
is the installation directory of Erlang/OTP, code:root_dir()
.
Directories can be named Name[-Vsn]
and the code server, by default, chooses
the directory with the highest version number among those having the same
Name
. Suffix -Vsn
is optional. If an ebin
directory exists under
Name[-Vsn]
, this directory is added to the code path.
Environment variable ERL_LIBS
(defined in the operating system) can be used to
define more library directories to be handled in the same way as the standard
OTP library directory described above, except that directories without an ebin
directory are ignored.
All application directories found in the additional directories appear before the standard OTP applications, except for the Kernel and STDLIB applications, which are placed before any additional applications. In other words, modules found in any of the additional library directories override modules with the same name in OTP, except for modules in Kernel and STDLIB.
Environment variable ERL_LIBS
(if defined) is to contain a colon-separated
(for Unix-like systems) or semicolon-separated (for Windows) list of additional
libraries.
Example:
On a Unix-like system, ERL_LIBS
can be set to the following:
/usr/local/jungerl:/home/some_user/my_erlang_lib
The code paths specified by $OTPROOT
, ERL_LIBS
, and boot scripts have their
listings cached by default (except for "."
) The code server will
lookup the contents in their directories once and avoid future file system
traversals. Therefore, modules added to such directories after the Erlang VM
boots will not be picked up. This behaviour can be disabled by setting
-cache_boot_paths false
or by calling code:set_path(code:get_path())
.
Change
The support for caching directories in the code path was added in Erlang/OTP 26.
Directories given by the command line options -pa
and -pz
are not
cached by default. Many of the functions that manipulate the code path
accept the cache
atom as an optional argument to enable caching
selectively.
Loading of Code From Archive Files
Change
The existing experimental support for archive files will be changed in a future release. As of Erlang/OTP 27, the function
code:lib_dir/2
, the-code_path_choice
flag, and usingerl_prim_loader
for reading files from an archive are deprecated.
escript
scripts that use archive files should useescript:extract/2
to read data files from its archive instead of usingcode:lib_dir/2
anderl_prim_loader
.
The Erlang archives are ZIP
files with extension .ez
. Erlang archives can
also be enclosed in escript
files whose file extension is arbitrary.
Erlang archive files can contain entire Erlang applications or parts of
applications. The structure in an archive file is the same as the directory
structure for an application. If you, for example, create an archive of
mnesia-4.4.7
, the archive file must be named mnesia-4.4.7.ez
and it must
contain a top directory named mnesia-4.4.7
. If the version part of the name is
omitted, it must also be omitted in the archive. That is, a mnesia.ez
archive
must contain a mnesia
top directory.
An archive file for an application can, for example, be created like this:
zip:create("mnesia-4.4.7.ez",
["mnesia-4.4.7"],
[{cwd, code:lib_dir()},
{compress, all},
{uncompress,[".beam",".app"]}]).
Any file in the archive can be compressed, but to speed up the access of
frequently read files, it can be a good idea to store beam
and app
files
uncompressed in the archive.
Normally the top directory of an application is located in library directory
$OTPROOT/lib
or in a directory referred to by environment variable ERL_LIBS
.
At startup, when the initial code path is computed, the code server also looks
for archive files in these directories and possibly adds ebin
directories in
archives to the code path. The code path then contains paths to directories that
look like $OTPROOT/lib/mnesia.ez/mnesia/ebin
or
$OTPROOT/lib/mnesia-4.4.7.ez/mnesia-4.4.7/ebin
.
The code server uses module erl_prim_loader
in ERTS (possibly through
erl_boot_server
) to read code files from archives. However, the functions in
erl_prim_loader
can also be used by other applications to read files from
archives. For example, the call
erl_prim_loader:list_dir( "/otp/root/lib/mnesia-4.4.7.ez/mnesia-4.4.7/examples/bench)"
would list the contents of a directory inside an archive. See
erl_prim_loader
.
An application archive file and a regular application directory can coexist.
This can be useful when it is needed to have parts of the application as regular
files. A typical case is the priv
directory, which must reside as a regular
directory to link in drivers dynamically and start port programs. For other
applications that do not need this, directory priv
can reside in the archive
and the files under the directory priv
can be read through erl_prim_loader
.
When a directory is added to the code path and when the entire code path is (re)set, the code server decides which subdirectories in an application that are to be read from the archive and which that are to be read as regular files. If directories are added or removed afterwards, the file access can fail if the code path is not updated (possibly to the same path as before, to trigger the directory resolution update).
For each directory on the second level in the application archive (ebin
,
priv
, src
, and so on), the code server first chooses the regular directory
if it exists and second from the archive. Function code:lib_dir/2
returns the
path to the subdirectory. For example, code:lib_dir(megaco, ebin)
can return
/otp/root/lib/megaco-3.9.1.1.ez/megaco-3.9.1.1/ebin
while
code:lib_dir(megaco, priv)
can return /otp/root/lib/megaco-3.9.1.1/priv
.
When an escript
file contains an archive, there are no restrictions on the
name of the escript
and no restrictions on how many applications that can be
stored in the embedded archive. Single Beam files can also reside on the top
level in the archive. At startup, the top directory in the embedded archive and
all (second level) ebin
directories in the embedded archive are added to the
code path. See escript
.
A future-proof way for escript
scripts to read data files from the archive is
to use the escript:extract/2
function.
When the choice of directories in the code path is strict
(which is
the default as of Erlang/OTP 27), the directory that ends up in the
code path is exactly the stated one. This means that if, for example,
the directory $OTPROOT/lib/mnesia-4.4.7/ebin
is explicitly added to
the code path, the code server does not load files from
$OTPROOT/lib/mnesia-4.4.7.ez/mnesia-4.4.7/ebin
.
This behavior can be controlled through command-line flag
-code_path_choice Choice
. If the flag is set to relaxed
, the code server
instead chooses a suitable directory depending on the actual file structure. If
a regular application ebin
directory exists, it is chosen. Otherwise, the
directory ebin
in the archive is chosen if it exists. If neither of them
exists, the original directory is chosen.
Command-line flag -code_path_choice Choice
also affects how module init
interprets the boot script
. The interpretation of the explicit code paths in
the boot script
can be strict
or relaxed
. It is particularly useful to set
the flag to relaxed
when elaborating with code loading from archives without
editing the boot script
. The default has changed to strict
in OTP 27 and the
option is scheduled for removal in OTP 28. See module init
in the
Erts application.
Current and Old Code
The code for a module can exist in two variants in a system: current code and old code. When a module is loaded into the system for the first time, the module code becomes current and the global export table is updated with references to all functions exported from the module.
When a new instance of the module is loaded, the code of the previous instance becomes old, and all export entries referring to the previous instance are removed. After that, the new instance is loaded as for the first time, and becomes current.
Both old and current code for a module are valid, and can even be executed concurrently. The difference is that exported functions in old code are unavailable. Hence, a global call cannot be made to an exported function in old code, but old code can still be executed because of processes lingering in it.
If a third instance of the module is loaded, the code server removes (purges) the old code and any processes lingering in it are terminated. Then the third instance becomes current and the previously current code becomes old.
For more information about old and current code, and how to make a process switch from old to current code, see section Compilation and Code Loading in the Erlang Reference Manual.
Native Coverage Support
In runtime systems that use the JIT, native coverage is a light-weight way to find out which functions or lines that have been executed, or how many times each function or line has been executed.
Change
The support for native coverage was added in Erlang/OTP 27.
Native coverage works by instrumenting code at load-time. When a
module has been instrumented for native coverage collection it is not
possible to later disable the coverage collection, except by reloading
the module. However, the overhead for keeping coverage collection
running is often neligible, especially for coverage
mode function
that only keeps track of which
functions that have been executed.
The cover
tool in the Tools application will automatically use the
native coverage support if the runtime system supports it.
It is only necessary to use the functionality described next if
cover
is not sufficient, for example:
If one wants to collect coverage information for the code that runs when the runtime system is starting (module
init
and so on).cover
can only be used when the Erlang system has started, and it will reload every module that is to be analyzed.If it is necessary to collect coverage information with the absolute minimum disturbance of the test system.
cover
always counts how many times each line is executed (coverage modeline_counters
), but by using native coverage one can use a less expensive coverage mode such asfunction
, which has almost negligible overhead.
Short summary of using native coverage
If the line
or line_counters
coverage mode is to be used,
the code to be tested must be compiled with option
line_coverage
.
Use set_coverage_mode(Mode) to set a
coverage mode for all code subsequently
loaded, or set it with option +JPcover
for erl
.
Optionally reset coverage information for all modules that are to be tested by calling reset_coverage(Module).
Run the code whose coverage information is to be collected.
Read out the counters for all interesting modules by calling
get_coverage(Level, Module), where Level
is either function
or line
.
The other native coverage BIFs
The following BIFs are sometimes useful, for example to fail gracefully if the runtime system does not support native coverage:
coverage_support() - check whether the runtime system supports native coverage
get_coverage_mode() - get the current coverage mode
get_coverage_mode(Module) - get the coverage mode for module
Module
Argument Types and Invalid Arguments
Module and application names are atoms, while file and directory names are strings. For backward compatibility reasons, some functions accept both strings and atoms, but a future release will probably only allow the arguments that are documented.
Functions in this module generally fail with an exception if they are passed an
incorrect type (for example, an integer or a tuple where an atom is expected).
An error tuple is returned if the argument type is correct, but there are some
other errors (for example, a non-existing directory is specified to
set_path/1
).
Error Reasons for Code-Loading Functions
Functions that load code (such as load_file/1
) will return
{error,Reason}
if the load operation fails. Here follows a description of the
common reasons.
badfile
- The object code has an incorrect format or the module name in the object code is not the expected module name.nofile
- No file with object code was found.not_purged
- The object code could not be loaded because an old version of the code already existed.on_load_failure
- The module has an -on_load function that failed when it was called.sticky_directory
- The object code resides in a sticky directory.
Summary
Types
An opaque term holding prepared code.
Functions
Equivalent to add_pathz(Dir, nocache)
.
Equivalent to add_pathz(Dir, Cache)
.
Equivalent to add_patha(Dir, nocache)
.
Adds Dir
to the beginning of the code path.
Equivalent to add_pathsz(Dirs, nocache)
.
Equivalent to add_pathsz(Dirs, Cache)
.
Equivalent to add_pathsa(Dirs, nocache)
.
Traverses Dirs
and adds each Dir
to the beginning of the code path.
Equivalent to add_pathsz(Dirs, nocache)
.
Adds the directories in Dirs
to the end of the code path.
Equivalent to add_pathz(Dir, nocache)
.
Adds Dir
as the directory last in the code path.
Returns a list of tuples {Module, Filename, Loaded}
for all available modules.
Returns a list of tuples {Module, Loaded}
for all loaded modules.
Tries to load all of the modules in the list Modules
atomically.
Searches all directories in the code path for module names with identical names
and writes a report to stdout
.
Clears the code path cache.
Returns the compiler library directory.
Returns true
if the system supports coverage and false
otherwise.
Deletes a directory from the code path.
Deletes directories from the code path.
Removes the current code for Module
, that is, the current code for Module
is
made old.
Tries to load a module in the same way as load_file/1
, unless the module is
already loaded.
Tries to load any modules not already loaded in the list Modules
in the same
way as load_file/1
.
Tries to load code for all modules that have been previously prepared by
prepare_loading/1
.
Return either function
or line
coverage data for module Module
.
Returns the coverage mode as set by option
+JPcover for erl
or set_coverage_mode/1
.
Get coverage mode for the given module.
Returns EEP 48 style
documentation for Module
if available.
Returns an atom describing the mode of the code server: interactive
or
embedded
.
Returns the object code for module Module
if found in the code path.
Returns the code path.
Checks whether Module
is loaded.
Returns true
if Module
is the name of a module that has been loaded from a
sticky directory (in other words: an attempt to reload the module will fail), or
false
if Module
is not a loaded module or is not sticky.
Returns the library directory, $OTPROOT/lib
, where $OTPROOT
is the root
directory of Erlang/OTP.
Returns the path for the library directory, the top directory, for an
application Name
located under $OTPROOT/lib
or in a directory referred to
with environment variable ERL_LIBS
.
Returns the path to a subdirectory directly under the top directory of an application.
Equivalent to load_file(Module)
, except that Filename
is
an absolute or relative filename.
Loads object code from a binary.
Tries to load the Erlang module Module
using the code path.
Returns the list of all currently loaded modules for which module_status/1
returns modified
.
See module_status/1
and all_loaded/0
for details.
Returns the status of Module
in relation to object file on disk.
Returns the object code file extension corresponding to the Erlang machine used.
Prepares to load the modules in the list Modules
.
Returns the path to the priv
directory in an application.
Purges the code for Module
, that is, removes code marked as old.
Equivalent to replace_path(Name, Dir, nocache)
.
Replaces an old occurrence of a directory named .../Name[-Vsn][/ebin]
in the
code path, with Dir
.
Resets coverage information for module Module
.
Returns the root directory of Erlang/OTP, which is the directory where it is installed.
Sets the coverage mode for modules that are subsequently loaded, similar to
option +JPcover for erl
.
Equivalent to set_path(PathList, nocache)
.
Sets the code path to the list of directories Path
.
Purges the code for Module
, that is, removes code marked as old, but only if
no processes linger in it.
Marks Dir
as sticky.
Unsticks a directory that is marked as sticky.
Searches the code path for Filename
, which is a file of arbitrary type.
If the module is not loaded, this function searches the code path for the first
file containing object code for Module
and returns the absolute filename.
Types
-type add_path_ret() :: true | {error, bad_directory}.
-type cache() :: cache | nocache.
-type coverage_mode() :: none | function | function_counters | line_coverage | line_counters.
-type load_error_rsn() :: badfile | nofile | not_purged | on_load_failure | sticky_directory.
-type load_ret() :: {error, What :: load_error_rsn()} | {module, Module :: module()}.
-type loaded_filename() :: (Filename :: file:filename()) | loaded_ret_atoms().
-type loaded_ret_atoms() :: cover_compiled | preloaded.
-type module_status() :: not_loaded | loaded | modified | removed.
-opaque prepared_code()
An opaque term holding prepared code.
-type replace_path_ret() :: true | {error, bad_directory | bad_name | {badarg, _}}.
-type set_path_ret() :: true | {error, bad_directory}.
Functions
-spec add_path(Dir) -> add_path_ret() when Dir :: file:filename().
Equivalent to add_pathz(Dir, nocache)
.
-spec add_path(Dir, cache()) -> add_path_ret() when Dir :: file:filename().
Equivalent to add_pathz(Dir, Cache)
.
-spec add_patha(Dir) -> add_path_ret() when Dir :: file:filename().
Equivalent to add_patha(Dir, nocache)
.
-spec add_patha(Dir, cache()) -> add_path_ret() when Dir :: file:filename().
Adds Dir
to the beginning of the code path.
If Dir
exists, it is removed from the old position in the code path.
Argument Cache
controls whether the content of the directory
should be cached on first traversal. If Cache
is cache
the directory
contents will be cached; if Cache
is nocache
it will not be cached.
Returns true
if successful, or {error, bad_directory}
if Dir
is
not the name of a directory.
-spec add_paths(Dirs) -> ok when Dirs :: [Dir :: file:filename()].
Equivalent to add_pathsz(Dirs, nocache)
.
-spec add_paths(Dirs, cache()) -> ok when Dirs :: [Dir :: file:filename()].
Equivalent to add_pathsz(Dirs, Cache)
.
-spec add_pathsa(Dirs) -> ok when Dirs :: [Dir :: file:filename()].
Equivalent to add_pathsa(Dirs, nocache)
.
-spec add_pathsa(Dirs, cache()) -> ok when Dirs :: [Dir :: file:filename()].
Traverses Dirs
and adds each Dir
to the beginning of the code path.
This means that the order of Dirs
is reversed in the resulting code
path. For example, if Dirs
is [Dir1,Dir2]
, the resulting path will
be [Dir2,Dir1|OldCodePath]
.
If a Dir
already exists in the code path, it is removed from the old position.
Argument Cache
controls whether the content of the directory
should be cached on first traversal. If Cache
is cache
the directory
contents will be cached; if Cache
is nocache
it will not be cached.
Always returns ok
, regardless of the validity of each individual Dir
.
-spec add_pathsz(Dirs) -> ok when Dirs :: [Dir :: file:filename()].
Equivalent to add_pathsz(Dirs, nocache)
.
-spec add_pathsz(Dirs, cache()) -> ok when Dirs :: [Dir :: file:filename()].
Adds the directories in Dirs
to the end of the code path.
Directories that are already present in the path will not be added.
Argument Cache
controls whether the content of the directory
should be cached on first traversal. If Cache
is cache
the directory
contents will be cached; if Cache
is nocache
it will not be cached.
Always returns ok
, regardless of the validity of each individual Dir
.
-spec add_pathz(Dir) -> add_path_ret() when Dir :: file:filename().
Equivalent to add_pathz(Dir, nocache)
.
-spec add_pathz(Dir, cache()) -> add_path_ret() when Dir :: file:filename().
Adds Dir
as the directory last in the code path.
If Dir
already exists in the path, it is not added.
Argument Cache
controls whether the content of the directory
should be cached on first traversal. If Cache
is cache
the directory
contents will be cached; if Cache
is nocache
it will not be cached.
Returns true
if successful, or {error, bad_directory}
if Dir
is
not the name of a directory.
-spec all_available() -> [{Module, Filename, Loaded}] when Module :: string(), Filename :: loaded_filename(), Loaded :: boolean().
Returns a list of tuples {Module, Filename, Loaded}
for all available modules.
A module is considered to be available if it either is loaded or would be loaded
if called. Filename
is normally the absolute filename, as described for
is_loaded/1
.
-spec all_loaded() -> [{Module, Loaded}] when Module :: module(), Loaded :: loaded_filename().
Returns a list of tuples {Module, Loaded}
for all loaded modules.
Loaded
is normally the absolute filename, as described for is_loaded/1
.
-spec atomic_load(Modules) -> ok | {error, [{Module, What}]} when Modules :: [Module | {Module, Filename, Binary}], Module :: module(), Filename :: file:filename(), Binary :: binary(), What :: badfile | nofile | on_load_not_allowed | duplicated | not_purged | sticky_directory | pending_on_load.
Tries to load all of the modules in the list Modules
atomically.
That means that either all modules are loaded at the same time, or none of the modules are loaded if there is a problem with any of the modules.
Loading can fail for one the following reasons:
badfile
- The object code has an incorrect format or the module name in the object code is not the expected module name.nofile
- No file with object code exists.on_load_not_allowed
- A module contains an -on_load function.duplicated
- A module is included more than once inModules
.not_purged
- The object code cannot be loaded because an old version of the code already exists.sticky_directory
- The object code resides in a sticky directory.pending_on_load
- A previously loaded module contains an-on_load
function that never finished.
If it is important to minimize the time that an application is inactive while
changing code, use prepare_loading/1
and finish_loading/1
instead of
atomic_load/1
. Here is an example:
{ok,Prepared} = code:prepare_loading(Modules),
%% Put the application into an inactive state or do any
%% other preparation needed before changing the code.
ok = code:finish_loading(Prepared),
%% Resume the application.
-spec clash() -> ok.
Searches all directories in the code path for module names with identical names
and writes a report to stdout
.
-spec clear_cache() -> ok.
Clears the code path cache.
If a directory is cached, its cache is cleared once and then it will be recalculated and cached once more in a future traversal.
To clear the cache for a single path, either re-add it to the code
path (with add_path/2
) or replace it (with
replace_path/3
). To disable all caching, reset
the code path with code:set_path(code:get_path())
.
Always returns ok
.
-spec compiler_dir() -> file:filename().
Returns the compiler library directory.
Equivalent to code:lib_dir(compiler)
.
-spec coverage_support() -> Supported when Supported :: boolean().
Returns true
if the system supports coverage and false
otherwise.
See also: Native Coverage Support
-spec del_path(NameOrDir) -> boolean() | {error, What} when NameOrDir :: Name | Dir, Name :: atom(), Dir :: file:filename(), What :: bad_name.
Deletes a directory from the code path.
The argument can be an atom Name
, in which case the directory with
the name .../Name[-Vsn][/ebin]
is deleted from the code path. Also,
the complete directory name Dir
can be specified as argument.
Returns:
true
- If successfulfalse
- If the directory is not found{error, bad_name}
- If the argument is invalid
-spec del_paths(NamesOrDirs) -> ok when NamesOrDirs :: [Name | Dir], Name :: atom(), Dir :: file:filename().
Deletes directories from the code path.
The argument is a list of either atoms or complete directory names. If
Name
is an atom, the directory with the name .../Name[-Vsn][/ebin]
is
deleted from the code path.
Always returns ok
, regardless of the validity of each individual
NamesOrDirs
.
Removes the current code for Module
, that is, the current code for Module
is
made old.
This means that processes can continue to execute the code in the module, but no external function calls can be made to it.
Returns true
if successful, or false
if there is old code for Module
that
must be purged first, or if Module
is not a (loaded) module.
-spec ensure_loaded(Module) -> {module, Module} | {error, What} when Module :: module(), What :: embedded | badfile | nofile | on_load_failure.
Tries to load a module in the same way as load_file/1
, unless the module is
already loaded.
If called concurrently, this function ensures that only one process attempts to load said module at a given time.
In embedded mode, it does not load a module that is not already loaded, but
returns {error, embedded}
instead. See
Error Reasons for Code-Loading Functions for a
description of other possible error reasons.
-spec ensure_modules_loaded([Module]) -> ok | {error, [{Module, What}]} when Module :: module(), What :: badfile | nofile | on_load_failure.
Tries to load any modules not already loaded in the list Modules
in the same
way as load_file/1
.
Unlike ensure_loaded/1
, modules are loaded even in embedded
mode.
Returns ok
if successful, or {error,[{Module,Reason}]}
if loading of some
modules fails. See
Error Reasons for Code-Loading Functions for a
description of other possible error reasons.
-spec finish_loading(Prepared) -> ok | {error, [{Module, What}]} when Prepared :: prepared_code(), Module :: module(), What :: not_purged | sticky_directory | pending_on_load.
Tries to load code for all modules that have been previously prepared by
prepare_loading/1
.
The loading occurs atomically, meaning that either all modules are loaded at the same time, or none of the modules are loaded.
This function can fail with one of the following error reasons:
not_purged
- The object code cannot be loaded because an old version of the code already exists.sticky_directory
- The object code resides in a sticky directory.pending_on_load
- A previously loaded module contains an-on_load
function that never finished.
-spec get_coverage(Level, module()) -> Result when Level :: function | line | cover_id_line, Result :: [{Entity, CoverageInfo}], Entity :: {Function, Arity} | Line | CoverId, CoverageInfo :: Covered | Counter, Function :: atom(), Arity :: arity(), Line :: non_neg_integer(), CoverId :: pos_integer(), Covered :: boolean(), Counter :: non_neg_integer().
Return either function
or line
coverage data for module Module
.
If Level is function
, returns function coverage for the given module
according to its coverage mode:
function
- For each function in module Module, a boolean indicating whether that function has been executed at least once is returned.function_counters
- For each function in module Module, an integer giving the number of times that line has been executed is returned.line
- For each function in module Module, a boolean indicating whether that function has been executed at least once is returned.line_counters
- For each function in module Module, a boolean indicating whether that function has been executed at least once is returned (note that in this mode, counters for the number of times each function has been executed cannot be retrieved).
If Level is line
, returns line coverage for the given module according to its
coverage mode:
line
- For each executable line in the module, a boolean indicating whether that line has been executed at least once is returned.line_counters
- For each executable line in the module, an integer giving the number of times that line was executed is returned.
Level cover_id_line
is used by the cover
tool.
Failures:
badarg
- IfLevel
is notfunction
orline
.badarg
- IfModule
is not an atom.badarg
- IfModule
does not refer to a loaded module.badarg
- IfModule
was not loaded in another coverage mode thannone
.badarg
- If Level isline
andModule
has not been loaded with eitherline
orline_counters
enabled.badarg
- If the runtime system does not support coverage.
See also: Native Coverage Support
-spec get_coverage_mode() -> Mode when Mode :: coverage_mode().
Returns the coverage mode as set by option
+JPcover for erl
or set_coverage_mode/1
.
Failure:
badarg
- If the runtime system does not support coverage.
See also: Native Coverage Support
-spec get_coverage_mode(Module) -> Mode when Module :: module(), Mode :: coverage_mode().
Get coverage mode for the given module.
Failures:
badarg
- IfModule
is not an atom.badarg
- IfModule
does not refer to a loaded module.badarg
- If the runtime system does not support coverage.
See also: Native Coverage Support
-spec get_doc(Mod) -> {ok, Res} | {error, Reason} when Mod :: module(), Res :: #docs_v1{anno :: term(), beam_language :: term(), format :: term(), module_doc :: term(), metadata :: term(), docs :: term()}, Reason :: non_existing | missing | file:posix().
Returns EEP 48 style
documentation for Module
if available.
If Module
is not found in the code path, this function returns
{error,non_existing}
.
If no documentation can be found this function attempts to generate
documentation from the debug information in the module. If no debug
information is available, this function returns {error,missing}
.
For more information about the documentation chunk see Documentation Storage and Format in Kernel's User's Guide.
-spec get_mode() -> embedded | interactive.
Returns an atom describing the mode of the code server: interactive
or
embedded
.
This information is useful when an external entity (for example, an IDE)
provides additional code for a running node. If the code server is in
interactive mode, it only has to add the path to the code. If the code server is
in embedded mode, the code must be loaded with load_binary/3
.
-spec get_object_code(Module) -> {Module, Binary, Filename} | error when Module :: module(), Binary :: binary(), Filename :: file:filename().
Returns the object code for module Module
if found in the code path.
Returns {Module, Binary, Filename}
if successful, otherwise
error
. Binary
is a binary data object, which contains the object
code for the module. This is useful if code is to be loaded on a
remote node in a distributed system. For example, loading module
Module
on a node Node
is done as follows:
...
{_Module, Binary, Filename} = code:get_object_code(Module),
erpc:call(Node, code, load_binary, [Module, Filename, Binary]),
...
-spec get_path() -> Path when Path :: [Dir :: file:filename()].
Returns the code path.
-spec is_loaded(Module) -> {file, Loaded} | false when Module :: module(), Loaded :: loaded_filename().
Checks whether Module
is loaded.
If it is, {file, Loaded}
is returned, otherwise false
.
Normally, Loaded
is the absolute filename Filename
from which the code is
obtained. If the module is preloaded (see script(4)
),
Loaded =:= preloaded
. If the module is Cover-compiled (see cover
),
Loaded =:= cover_compiled
.
Returns true
if Module
is the name of a module that has been loaded from a
sticky directory (in other words: an attempt to reload the module will fail), or
false
if Module
is not a loaded module or is not sticky.
-spec lib_dir() -> file:filename().
Returns the library directory, $OTPROOT/lib
, where $OTPROOT
is the root
directory of Erlang/OTP.
Example:
1> code:lib_dir().
"/usr/local/otp/lib"
-spec lib_dir(Name) -> file:filename() | {error, bad_name} when Name :: atom().
Returns the path for the library directory, the top directory, for an
application Name
located under $OTPROOT/lib
or in a directory referred to
with environment variable ERL_LIBS
.
If a regular directory called Name
or Name-Vsn
exists in the code path with
an ebin
subdirectory, the path to this directory is returned (not the ebin
directory).
If the directory refers to a directory in an archive, the archive name is
stripped away before the path is returned. For example, if directory
/usr/local/otp/lib/mnesia-4.2.2.ez/mnesia-4.2.2/ebin
is in the path,
/usr/local/otp/lib/mnesia-4.2.2/ebin
is returned. This means that the library
directory for an application is the same, regardless if the application resides
in an archive or not.
Warning
Archives are experimental. In a future release, they can be removed or their behavior can change.
Example:
> code:lib_dir(mnesia).
"/usr/local/otp/lib/mnesia-4.23"
Returns {error, bad_name}
if Name
is not the name of an application under
$OTPROOT/lib
or on a directory referred to through environment variable
ERL_LIBS
. Fails with an exception if Name
has the wrong type.
Warning
For backward compatibility,
Name
is also allowed to be a string. That will probably change in a future release.
-spec lib_dir(Name, SubDir) -> file:filename() | {error, bad_name} when Name :: atom(), SubDir :: atom().
Returns the path to a subdirectory directly under the top directory of an application.
Change
This function is part of the archive support, which is an experimental feature that will be changed or removed in a future release.
Normally the subdirectories reside under the top directory for the application, but when applications at least partly reside in an archive, the situation is different. Some of the subdirectories can reside as regular directories while others reside in an archive file. It is not checked whether this directory exists.
Instead of using this function, use code:lib_dir/1
and filename:join/2
.
Example:
1> filename:join(code:lib_dir(megaco), "priv").
"/usr/local/otp/lib/megaco-3.9.1.1/priv"
Fails with an exception if Name
or SubDir
has the wrong type.
-spec load_abs(Filename) -> load_ret() when Filename :: file:filename().
Equivalent to load_file(Module)
, except that Filename
is
an absolute or relative filename.
The code path is not searched. It returns a value in the same way as
load_file/1
. Notice that Filename
must not contain the extension
(for example, .beam
) because load_abs/1
adds the
correct extension.
-spec load_binary(Module, Filename, Binary) -> {module, Module} | {error, What} when Module :: module(), Filename :: loaded_filename(), Binary :: binary(), What :: badarg | load_error_rsn().
Loads object code from a binary.
This function can be used to load object code on remote Erlang nodes. Argument
Binary
must contain object code for Module
. Filename
is only used by the
code server to keep a record of from which file the object code for Module
originates. Thus, Filename
is not opened and read by the code server.
Returns {module, Module}
if successful, or {error, Reason}
if loading fails.
See Error Reasons for Code-Loading Functions for a
description of the possible error reasons.
Tries to load the Erlang module Module
using the code path.
It looks for the object code file with an extension corresponding to
the Erlang machine used, for example, Module.beam
. The loading fails
if the module name found in the object code differs from the name
Module
. Use load_binary/3
to load object code with a module name
that is different from the file name.
Returns {module, Module}
if successful, or {error, Reason}
if loading fails.
See Error Reasons for Code-Loading Functions for a
description of the possible error reasons.
-spec modified_modules() -> [module()].
Returns the list of all currently loaded modules for which module_status/1
returns modified
.
See also all_loaded/0
.
-spec module_status() -> [{module(), module_status()}].
See module_status/1
and all_loaded/0
for details.
-spec module_status(Module :: module() | [module()]) -> module_status() | [{module(), module_status()}].
Returns the status of Module
in relation to object file on disk.
The status of a module can be one of:
not_loaded
- IfModule
is not currently loaded.loaded
- IfModule
is loaded, and the object file exists and contains the same code.removed
- IfModule
is loaded, but no corresponding object file can be found in the code path.modified
- IfModule
is loaded, but the object file contains code with a different MD5 checksum.
Preloaded modules are always reported as loaded
, without inspecting the
contents on disk. Cover-compiled modules will always be reported as modified
if an object file exists, or as removed
otherwise. Modules whose load path is
an empty string (which is the convention for auto-generated code) will only be
reported as loaded
or not_loaded
.
See also modified_modules/0
.
-spec objfile_extension() -> nonempty_string().
Returns the object code file extension corresponding to the Erlang machine used.
For the official Erlang/OTP release, the return value is always .beam
.
-spec prepare_loading(Modules) -> {ok, Prepared} | {error, [{Module, What}]} when Modules :: [Module | {Module, Filename, Binary}], Module :: module(), Filename :: file:filename(), Binary :: binary(), Prepared :: prepared_code(), What :: badfile | nofile | on_load_not_allowed | duplicated.
Prepares to load the modules in the list Modules
.
Finish the loading by calling finish_loading(Prepared).
This function can fail with one of the following error reasons:
badfile
- The object code has an incorrect format or the module name in the object code is not the expected module name.nofile
- No file with object code exists.on_load_not_allowed
- A module contains an -on_load function.duplicated
- A module is included more than once inModules
.
-spec priv_dir(Name) -> file:filename() | {error, bad_name} when Name :: atom().
Returns the path to the priv
directory in an application.
Warning
For backward compatibility,
Name
is also allowed to be a string. That will probably change in a future release.
Purges the code for Module
, that is, removes code marked as old.
If some processes still linger in the old code, these processes are killed before the code is removed.
Change
As of Erlang/OTP 20.0, a process is only considered to be lingering in the code if it has direct references to the code. For more information see documentation of
erlang:check_process_code/3
, which is used in order to determine whether a process is lingering.
Returns true
if successful and any process is needed to be killed, otherwise
false
.
-spec replace_path(Name, Dir) -> replace_path_ret() when Name :: atom(), Dir :: file:filename().
Equivalent to replace_path(Name, Dir, nocache)
.
-spec replace_path(Name, Dir, cache()) -> replace_path_ret() when Name :: atom(), Dir :: file:filename().
Replaces an old occurrence of a directory named .../Name[-Vsn][/ebin]
in the
code path, with Dir
.
If Name
does not exist, it adds the new directory Dir
last in the
code path. The new directory must also be named
.../Name[-Vsn][/ebin]
. This function is to be used if a new version
of the directory (library) is added to a running system.
Argument Cache
controls whether the content of the directory
should be cached on first traversal. If Cache
is cache
the directory
contents will be cached; if Cache
is nocache
it will not be cached.
Returns:
true
- If successful{error, bad_name}
- IfName
is not found{error, bad_directory}
- IfDir
does not exist{error, {badarg, [Name, Dir]}}
- IfName
orDir
is invalid
-spec reset_coverage(Module) -> ok when Module :: module().
Resets coverage information for module Module
.
If the coverage mode is either function
or
line
, all booleans for Module
keeping track of executed functions
or lines are set to false
.
If the coverage mode is either function_counters
or
line_counters
, all counters for Module
are reset to zero.
Failures:
badarg
- IfModule
is not an atom.badarg
- IfModule
does not refer to a loaded module.badarg
- IfModule
was not loaded with coverage enabled.badarg
- If the runtime system does not support coverage.
See also: Native Coverage Support
-spec root_dir() -> file:filename().
Returns the root directory of Erlang/OTP, which is the directory where it is installed.
Example:
1> code:root_dir().
"/usr/local/otp"
-spec set_coverage_mode(Mode) -> OldMode when Mode :: coverage_mode(), OldMode :: coverage_mode().
Sets the coverage mode for modules that are subsequently loaded, similar to
option +JPcover for erl
.
The coverage mode will have the following effect on code that is loaded following this call:
function
- All modules that are loaded will be instrumented to keep track of which functions are executed. Information about which functions that have been executed can be retrieved by callingget_coverage(function, Module)
.function_counters
- All modules that are loaded will be instrumented to count how many times each function is executed. Information about how many times each function has been executed can be retrieved by callingget_coverage(function, Module)
.line
- When modules that have been compiled with theline_coverage
option are loaded, they will be instrumented to keep track of which lines have been executed. Information about which lines have been executed can be retrieved by callingget_coverage(line, Module)
, and information about which functions that have been executed can be retrieved by callingget_coverage(function, Module)
.line_counters
- When modules that have been compiled with theline_coverage
option are loaded, they will be instrumented to count the number of times each line is executed. Information about how many times each line has been executed can be retrieved by callingget_coverage(line, Module)
, and information about which functions that have been executed can be retrieved by callingget_coverage(function, Module)
(note that in this mode, counters for the number of times each function has been executed cannot be retrieved).none
- Modules will be loaded without coverage instrumentation.
Returns the previous coverage mode.
Failures:
badarg
- IfMode
is not a valid coverage mode.badarg
- If the runtime system does not support coverage.
See also: Native Coverage Support
-spec set_path(Path) -> set_path_ret() when Path :: [Dir :: file:filename()].
Equivalent to set_path(PathList, nocache)
.
-spec set_path(Path, cache()) -> set_path_ret() when Path :: [Dir :: file:filename()].
Sets the code path to the list of directories Path
.
Argument Cache
controls whether the content of the directory
should be cached on first traversal. If Cache
is cache
the directory
contents will be cached; if Cache
is nocache
it will not be cached.
Returns:
true
- If successful{error, bad_directory}
- If anyDir
is not a directory name
Purges the code for Module
, that is, removes code marked as old, but only if
no processes linger in it.
Change
As of Erlang/OTP 20.0, a process is only considered to be lingering in the code if it has direct references to the code. For more information see documentation of
erlang:check_process_code/3
, which is used in order to determine whether a process is lingering.
Returns false
if the module cannot be purged because of processes lingering in
old code, otherwise true
.
-spec stick_dir(Dir) -> ok | error when Dir :: file:filename().
Marks Dir
as sticky.
Returns ok
if successful, otherwise error
.
-spec unstick_dir(Dir) -> ok | error when Dir :: file:filename().
Unsticks a directory that is marked as sticky.
Returns ok
if successful, otherwise error
.
-spec where_is_file(Filename) -> non_existing | Absname when Filename :: file:filename(), Absname :: file:filename().
Searches the code path for Filename
, which is a file of arbitrary type.
If found, the full name is returned. non_existing
is returned if the
file cannot be found. The function can be useful, for example, to
locate application resource files.
-spec which(Module) -> Which when Module :: module(), Which :: loaded_filename() | non_existing.
If the module is not loaded, this function searches the code path for the first
file containing object code for Module
and returns the absolute filename.
If the module is loaded, it returns the name of the file containing the loaded object code.
If the module is preloaded,
preloaded
is returned.If the module is Cover-compiled,
cover_compiled
is returned.If the module cannot be found,
non_existing
is returned.