View Source IEx.Helpers (IEx v1.16.1)
Welcome to Interactive Elixir. You are currently
seeing the documentation for the module IEx.Helpers
which provides many helpers to make Elixir's shell
more joyful to work with.
This message was triggered by invoking the helper h()
,
usually referred to as h/0
(since it expects 0 arguments).
You can use the h/1
function to invoke the documentation
for any Elixir module or function:
iex> h(Enum)
iex> h(Enum.map)
iex> h(Enum.reverse/1)
You can also use the i/1
function to introspect any value
you have in the shell:
iex> i("hello")
There are many other helpers available, here are some examples:
b/1
- prints callbacks info and docs for a given modulec/1
- compiles a filec/2
- compiles a file and writes bytecode to the given pathcd/1
- changes the current directoryclear/0
- clears the screenexports/1
- shows all exports (functions + macros) in a moduleflush/0
- flushes all messages sent to the shellh/0
- prints this help messageh/1
- prints help for the given module, function or macroi/0
- prints information about the last valuei/1
- prints information about the given termls/0
- lists the contents of the current directoryls/1
- lists the contents of the specified directoryopen/1
- opens the source for the given module or function in your editorpid/1
- creates a PID from a stringpid/3
- creates a PID with the 3 integer arguments passedport/1
- creates a port from a stringport/2
- creates a port with the 2 non-negative integers passedpwd/0
- prints the current working directoryr/1
- recompiles the given module's source filerecompile/0
- recompiles the current projectref/1
- creates a reference from a stringref/4
- creates a reference with the 4 integer arguments passedruntime_info/0
- prints runtime info (versions, memory usage, stats)t/1
- prints the types for the given module or functionv/0
- retrieves the last value from the historyv/1
- retrieves the nth value from the history
Help for all of those functions can be consulted directly from
the command line using the h/1
helper itself. Try:
iex> h(v/0)
To list all IEx helpers available, which is effectively all
exports (functions and macros) in the IEx.Helpers
module:
iex> exports(IEx.Helpers)
This module also includes helpers for debugging purposes, see
IEx.break!/4
for more information.
To learn more about IEx as a whole, type h(IEx)
.
Summary
Functions
Prints the documentation for the given callback function.
Sets up a breakpoint in the AST of shape Module.function/arity
with the given number of stops
.
Sets up a breakpoint in module
, function
and arity
with the given number of stops
.
Prints all breakpoints to the terminal.
Compiles the given files.
Changes the current working directory to the given path.
Clears the console screen.
Continues execution of the current process.
Prints a list of all the functions and macros exported by the given module.
Clears out all messages sent to the shell's inbox and prints them out.
Prints the documentation for IEx.Helpers
.
Prints the documentation for the given module
or for the given function/arity
pair.
Prints information about the data type of any given term.
Injects the contents of the file at path
.
Similar to import_file
but only imports the file if it is available.
Calls import/2
with the given arguments, but only if the module is available.
Loads the given module's BEAM code (and ensures any previous old version was properly purged before).
Prints a list of the given directory's contents.
Goes to the next line of the current breakpoint.
Deploys a given module's BEAM code to a list of nodes.
Opens the current prying location.
Opens the given module
, module.function/arity
, or {file, line}
.
Creates a PID from string
or atom
.
Creates a PID with 3 non-negative integers passed as arguments to the function.
Creates a Port from string
.
Creates a Port from two non-negative integers.
Prints the current working directory.
Recompiles and reloads the given module
or modules
.
Recompiles the current Mix project.
Creates a Reference from string
.
Creates a Reference from its 4 non-negative integers components.
Removes all breakpoints and instrumentation from all modules.
Removes all breakpoints and instrumentation from module
.
Sets the number of pending stops in the breakpoint
with the given id
to zero.
Sets the number of pending stops in the given module, function and arity to zero.
Respawns the current shell by starting a new shell process.
Prints VM/runtime information such as versions, memory usage and statistics.
Just like runtime_info/0
, except accepts topic or a list of topics.
Prints the types for the given module or for the given function/arity pair.
Calls use/2
with the given arguments, but only if the module is available.
Returns the value of the n
th expression in the history.
Prints the current location and stacktrace in a pry session.
Functions
Prints the documentation for the given callback function.
It also accepts single module argument to list all available behaviour callbacks.
Examples
iex> b(Mix.Task.run/1)
iex> b(Mix.Task.run)
iex> b(GenServer)
Sets up a breakpoint in the AST of shape Module.function/arity
with the given number of stops
.
See IEx.break!/4
for a complete description of breakpoints
in IEx.
Examples
break! URI.decode_query/2
Sets up a breakpoint in module
, function
and arity
with the given number of stops
.
See IEx.break!/4
for a complete description of breakpoints
in IEx.
Examples
break! URI, :decode_query, 2
Prints all breakpoints to the terminal.
Compiles the given files.
It expects a list of files to compile and an optional path to write the compiled code to. By default files are in-memory compiled. To write compiled files to the current directory, an empty string can be given.
It returns the names of the compiled modules.
If you want to recompile an existing module, check r/1
instead.
Examples
In the example below, we pass a directory to where the c/2
function will
write the compiled .beam
files to. This directory is typically named "ebin"
in Erlang/Elixir systems:
iex> c(["foo.ex", "bar.ex"], "ebin")
[Foo, Bar]
When compiling one file, there is no need to wrap it in a list:
iex> c("baz.ex")
[Baz]
Changes the current working directory to the given path.
Clears the console screen.
This function only works if ANSI escape codes are enabled on the shell, which means this function is by default unavailable on Windows machines.
Continues execution of the current process.
This is usually called by sessions started with IEx.pry/0
or IEx.break!/4
. This allows the current process to execute
until the next breakpoint, which will automatically yield control
back to IEx without requesting permission to pry.
If you simply want to move to the next line of the current breakpoint,
use n/0
or next/0
instead.
If the running process terminates, a new IEx session is started.
While the process executes, the user will no longer have
control of the shell. If you would rather start a new shell,
use respawn/0
instead.
Prints a list of all the functions and macros exported by the given module.
Clears out all messages sent to the shell's inbox and prints them out.
Prints the documentation for IEx.Helpers
.
Prints the documentation for the given module
or for the given function/arity
pair.
Examples
iex> h(Enum)
It also accepts functions in the format function/arity
and module.function/arity
, for example:
iex> h(receive/1)
iex> h(Enum.all?/2)
iex> h(Enum.all?)
Prints information about the data type of any given term.
If no argument is given, the value of the previous expression is used.
Examples
iex> i(1..5)
Will print:
Term
1..5
Data type
Range
Description
This is a struct. Structs are maps with a __struct__ key.
Reference modules
Range, Map
Injects the contents of the file at path
.
This would be the equivalent of getting all of the file contents and pasting it all at once in IEx and executing it.
By default, the contents of a .iex.exs
file in the same directory
as you are starting IEx are automatically imported. See the section
for ".iex.exs" in the IEx
module docs for more information.
path
has to be a literal string and is automatically expanded via
Path.expand/1
.
Examples
# ~/file.exs
value = 13
# in the shell
iex(1)> import_file("~/file.exs")
13
iex(2)> value
13
Similar to import_file
but only imports the file if it is available.
By default, import_file/1
fails when the given file does not exist.
However, since import_file/1
is expanded at compile-time, it's not
possible to conditionally import a file since the macro is always
expanded:
# This raises a File.Error if ~/.iex.exs doesn't exist.
if "~/.iex.exs" |> Path.expand() |> File.exists?() do
import_file("~/.iex.exs")
end
This macro addresses this issue by checking if the file exists or not in behalf of the user.
Calls import/2
with the given arguments, but only if the module is available.
This lets you put imports in .iex.exs
files (including ~/.iex.exs
) without
getting compile errors if you open a console where the module is not available.
Example
# In ~/.iex.exs
import_if_available(Ecto.Query)
Loads the given module's BEAM code (and ensures any previous old version was properly purged before).
This function is useful when you know the bytecode for module has been updated in the file system and you want to tell the VM to load it.
Prints a list of the given directory's contents.
If path
points to a file, prints its full path.
A shortcut for next/0
.
Goes to the next line of the current breakpoint.
This is usually called by sessions started with IEx.break!/4
.
If instead of the next line you want to move to the next breakpoint,
call continue/0
instead.
While the process executes, the user will no longer have
control of the shell. If you would rather start a new shell,
use respawn/0
instead.
Deploys a given module's BEAM code to a list of nodes.
This function is useful for development and debugging when you have code that has been compiled or updated locally that you want to run on other nodes.
The node list defaults to a list of all connected nodes.
Returns {:error, :nofile}
if the object code (i.e. ".beam" file) for the module
could not be found locally.
Examples
iex> nl(HelloWorld)
{:ok,
[
{:node1@easthost, :loaded, HelloWorld},
{:node1@westhost, :loaded, HelloWorld}
]}
iex> nl(NoSuchModuleExists)
{:error, :nofile}
Opens the current prying location.
This command only works inside a pry session started manually
via IEx.pry/0
or a breakpoint set via IEx.break!/4
. Calling
this function during a regular IEx
session will print an error.
Keep in mind the open/0
location may not exist when prying
precompiled source code, such as Elixir itself.
For more information and to open any module or function, see
open/1
.
Opens the given module
, module.function/arity
, or {file, line}
.
This function uses the ELIXIR_EDITOR
environment variable
and falls back to EDITOR
if the former is not available.
By default, it attempts to open the file and line using the
file:line
notation. For example, for Sublime Text you can
set it as:
ELIXIR_EDITOR="subl"
Which will then try to open it as:
subl path/to/file:line
For Visual Studio Code, once enabled on the command line, you can set it to:
ELIXIR_EDITOR="code --goto"
It is important that you choose an editor command that does not block nor that attempts to run an editor directly in the terminal. Command-line based editors likely need extra configuration so they open up the given file and line in a separate window.
For more complex use cases, you can use the __FILE__
and
__LINE__
notations to explicitly interpolate the file and
line into the command:
ELIXIR_EDITOR="my_editor +__LINE__ __FILE__"
Since this function prints the result returned by the editor,
ELIXIR_EDITOR
can be set "echo" if you prefer to display the
location rather than opening it.
Keep in mind the location may not exist when opening precompiled source code.
Examples
iex> open(MyApp)
iex> open(MyApp.fun/2)
iex> open({"path/to/file", 1})
Creates a PID from string
or atom
.
Examples
iex> pid("0.21.32")
#PID<0.21.32>
iex> pid("#PID<0.21.32>")
#PID<0.21.32>
iex> pid(:init)
#PID<0.0.0>
Creates a PID with 3 non-negative integers passed as arguments to the function.
Examples
iex> pid(0, 21, 32)
#PID<0.21.32>
iex> pid(0, 64, 2048)
#PID<0.64.2048>
Creates a Port from string
.
Examples
iex> port("0.4")
#Port<0.4>
Creates a Port from two non-negative integers.
Examples
iex> port(0, 8080)
#Port<0.8080>
iex> port(0, 443)
#Port<0.443>
Prints the current working directory.
Recompiles and reloads the given module
or modules
.
Please note that all the modules defined in the same file as
modules
are recompiled and reloaded. If you want to reload
multiple modules, it is best to reload them at the same time,
such as in r [Foo, Bar]
. This is important to avoid false
warnings, since the module is only reloaded in memory and its
latest information is not persisted to disk. See the "In-memory
reloading" section below.
This function is meant to be used for development and debugging purposes. Do not depend on it in production code.
In-memory reloading
When we reload the module in IEx, we recompile the module source
code, updating its contents in memory. The original .beam
file
in disk, probably the one where the first definition of the module
came from, does not change at all.
Since docs, typespecs, and exports information are loaded from the .beam file, they are not reloaded when you invoke this function.
Recompiles the current Mix project.
This helper only works when IEx is started with a Mix
project, for example, iex -S mix
. Note this function
simply recompiles Elixir modules, without reloading
configuration, recompiling dependencies, or restarting
applications.
Therefore, any long running process may crash on recompilation, as changed modules will be temporarily removed and recompiled, without going through the proper code change callback.
If you want to reload a single module, consider using
r(ModuleName)
instead.
This function is meant to be used for development and debugging purposes. Do not depend on it in production code.
Options
:force
- whentrue
, forces the application to recompile
Creates a Reference from string
.
Examples
iex> ref("0.1.2.3")
#Reference<0.1.2.3>
Creates a Reference from its 4 non-negative integers components.
Examples
iex> ref(0, 1, 2, 3)
#Reference<0.1.2.3>
Removes all breakpoints and instrumentation from all modules.
Removes all breakpoints and instrumentation from module
.
Sets the number of pending stops in the breakpoint
with the given id
to zero.
Returns :ok
if there is such breakpoint ID. :not_found
otherwise.
Note the module remains "instrumented" on reset. If you would
like to effectively remove all breakpoints and instrumentation
code from a module, use remove_breaks/1
instead.
Sets the number of pending stops in the given module, function and arity to zero.
If the module is not instrumented or if the given function
does not have a breakpoint, it is a no-op and it returns
:not_found
. Otherwise it returns :ok
.
Note the module remains "instrumented" on reset. If you would
like to effectively remove all breakpoints and instrumentation
code from a module, use remove_breaks/1
instead.
Respawns the current shell by starting a new shell process.
Prints VM/runtime information such as versions, memory usage and statistics.
Additional topics are available via runtime_info/1
.
For more metrics, info, and debugging facilities, see the Recon project.
Just like runtime_info/0
, except accepts topic or a list of topics.
For example, topic :applications
will list the applications loaded.
Prints the types for the given module or for the given function/arity pair.
Examples
iex> t(Enum)
@type t() :: Enumerable.t()
@type acc() :: any()
@type element() :: any()
@type index() :: integer()
@type default() :: any()
iex> t(Enum.t/0)
@type t() :: Enumerable.t()
iex> t(Enum.t)
@type t() :: Enumerable.t()
Calls use/2
with the given arguments, but only if the module is available.
This lets you use the module in .iex.exs
files (including ~/.iex.exs
) without
getting compile errors if you open a console where the module is not available.
Example
# In ~/.iex.exs
use_if_available(Phoenix.HTML)
Returns the value of the n
th expression in the history.
n
can be a negative value: if it is, the corresponding expression value
relative to the current one is returned. For example, v(-2)
returns the
value of the expression evaluated before the last evaluated expression. In
particular, v(-1)
returns the result of the last evaluated expression and
v()
does the same.
Examples
iex(1)> "hello" <> " world"
"hello world"
iex(2)> 40 + 2
42
iex(3)> v(-2)
"hello world"
iex(4)> v(2)
42
iex(5)> v()
42
Prints the current location and stacktrace in a pry session.
It expects a radius
which chooses how many lines before and after
the current line we should print. By default the radius
is of two
lines:
Location: lib/iex/lib/iex/helpers.ex:79
77:
78: def recompile do
79: require IEx; IEx.pry()
80: if mix_started?() do
81: config = Mix.Project.config
(IEx.Helpers) lib/iex/lib/iex/helpers.ex:78: IEx.Helpers.recompile/0
This command only works inside a pry session started manually
via IEx.pry/0
or a breakpoint set via IEx.break!/4
. Calling
this function during a regular IEx
session will print an error.
Keep in mind the whereami/1
location may not exist when prying
precompiled source code, such as Elixir itself.