### Agent.start/2 example

Source: https://elixir.hexdocs.pm/Agent.html

IEx example showing how to start an agent with an initial state and retrieve it using Agent.get/2.

```elixir
iex> {:ok, pid} = Agent.start(fn -> 42 end)
iex> Agent.get(pid, fn state -> state end)
42
```

--------------------------------

### Agent.start_link/2 example

Source: https://elixir.hexdocs.pm/Agent.html

IEx example showing successful start and retrieval, and a failure case where the function raises an error.

```elixir
iex> {:ok, pid} = Agent.start_link(fn -> 42 end)
iex> Agent.get(pid, fn state -> state end)
42

iex> {:error, {exception, _stacktrace}} = Agent.start(fn -> raise "oops" end)
iex> exception
%RuntimeError{message: "oops"}
```

--------------------------------

### Agent stop/3 example

Source: https://elixir.hexdocs.pm/Agent.html

IEx example showing how to start an agent and stop it, returning :ok.

```elixir
iex> {:ok, pid} = Agent.start_link(fn -> 42 end)
iex> Agent.stop(pid)
:ok
```

--------------------------------

### Node.start example

Source: https://elixir.hexdocs.pm/Node.md

Example of starting a distributed node with Node.start/2, using the :shortnames name domain and hidden: true. Returns {:ok, pid} on success.

```elixir
{:ok, pid} = Node.start(:example, name_domain: :shortnames, hidden: true)
```

--------------------------------

### Start a single DynamicSupervisor

Source: https://elixir.hexdocs.pm/PartitionSupervisor.md

Baseline setup: starts one DynamicSupervisor named MyApp.DynamicSupervisor under a Supervisor with :one_for_one strategy.

```elixir
children = [
  {DynamicSupervisor, name: MyApp.DynamicSupervisor}
]

Supervisor.start_link(children, strategy: :one_for_one)
```

--------------------------------

### Range.size/1 examples

Source: https://elixir.hexdocs.pm/Range.html

Examples of using Range.size/1 to get the number of elements in ranges with various steps. Note that ranges with a step that does not align with the start and end can produce zero or reduced sizes.

```elixir
iex> Range.size(1..10)
10
iex> Range.size(1..10//2)
5
iex> Range.size(1..10//3)
4
iex> Range.size(1..10//-1)
0

iex> Range.size(10..1//-1)
10
iex> Range.size(10..1//-2)
5
iex> Range.size(10..1//-3)
4
iex> Range.size(10..1//1)
0
```

--------------------------------

### start_link examples

Source: https://elixir.hexdocs.pm/Agent.md

IEx examples showing successful start_link and error handling when the function raises.

```elixir
iex> {:ok, pid} = Agent.start_link(fn -> 42 end)
iex> Agent.get(pid, fn state -> state end)
42
```

```elixir
iex> {:error, {exception, _stacktrace}} = Agent.start(fn -> raise "oops" end)
iex> exception
%RuntimeError{message: "oops"}
```

--------------------------------

### Date.day_of_week/2 usage examples

Source: https://elixir.hexdocs.pm/Date.html

Examples of calling Date.day_of_week/2 with various dates and starting weekdays, demonstrating the default Monday start and the :sunday option.

```elixir
# 2016-10-31 is a Monday and by default Monday is the first day of the week
iex> Date.day_of_week(~D[2016-10-31])
1
iex> Date.day_of_week(~D[2016-11-01])
2
iex> Date.day_of_week(~N[2016-11-01 01:23:45])
2
iex> Date.day_of_week(~D[-0015-10-30])
3

# 2016-10-31 is a Monday but, as we start the week on Sunday, now it returns 2
iex> Date.day_of_week(~D[2016-10-31], :sunday)
2
iex> Date.day_of_week(~D[2016-11-01], :sunday)
3
iex> Date.day_of_week(~N[2016-11-01 01:23:45], :sunday)
3
iex> Date.day_of_week(~D[-0015-10-30], :sunday)
4
```

--------------------------------

### iterate example

Source: https://elixir.hexdocs.pm/Stream.md

Example showing iterate doubling values starting from 1.

```elixir
iex> Stream.iterate(1, &(&1 * 2)) |> Enum.take(5)
[1, 2, 4, 8, 16]
```

--------------------------------

### mkdir! examples

Source: https://elixir.hexdocs.pm/File.md

Examples showing mkdir! returning :ok for a successful creation and raising a File.Error when a parent directory is missing.

```elixir
File.mkdir!("test/unit")
#=> :ok
```

```elixir
File.mkdir!("non/existing")
** (File.Error) could not make directory "non/existing": no such file or directory
```

--------------------------------

### Process.demonitor/2 example

Source: https://elixir.hexdocs.pm/Process.md

Example showing how to create a monitor and then demonitor it, returning true.

```elixir
pid = spawn(fn -> 1 + 2 end)
ref = Process.monitor(pid)
Process.demonitor(ref)
#=> true
```

--------------------------------

### URI.default_port/1 examples

Source: https://elixir.hexdocs.pm/URI.html

Examples of getting default ports for known and unknown schemes.

```elixir
iex> URI.default_port("ftp")
21

iex> URI.default_port("ponzi")
nil
```

--------------------------------

### Example config/runtime.exs for :my_app

Source: https://elixir.hexdocs.pm/Application.html

Example configuration file for an OTP application :my_app, defining database configurations and a list of repositories.

```elixir
config :my_app, Databases.RepoOne,
  # A database configuration
  ip: "localhost",
  port: 5433

config :my_app, Databases.RepoTwo,
  # Another database configuration (for the same OTP app)
  ip: "localhost",
  port: 20_717

config :my_app, my_app_databases: [Databases.RepoOne, Databases.RepoTwo]
```

--------------------------------

### String.slice/3 with negative start

Source: https://elixir.hexdocs.pm/String.html

Examples of String.slice/3 with negative start positions. The start is normalized against the string length and clamped to 0.

```elixir
iex> String.slice("elixir", -4, 4)
"ixir"

iex> String.slice("elixir", -10, 3)
"eli"
```

--------------------------------

### iodata_length/1 example

Source: https://elixir.hexdocs.pm/IO.html

Example showing how to get the length of IO data using iodata_length/1.

```elixir
iex> IO.iodata_length([1, 2 | <<3, 4>>])
4
```

--------------------------------

### Start an application with Application.start/1

Source: https://elixir.hexdocs.pm/Application.html

Starts the application :ex_unit, returning :ok. Starting automatically loads the application if not already loaded and checks that dependencies are started.

```elixir
Application.start(:ex_unit)
#=> :ok
```

--------------------------------

### Enum.drop_while/2 example

Source: https://elixir.hexdocs.pm/Enum.md

Example showing Enum.drop_while/2 dropping elements less than 3 from the start of the list.

```elixir
iex> Enum.drop_while([1, 2, 3, 2, 1], fn x -> x < 3 end)
[3, 2, 1]
```

--------------------------------

### Port.open example with cat command

Source: https://elixir.hexdocs.pm/Port.md

Example showing how to open a port to spawn the 'cat' program, send data, receive responses, and close the port. Demonstrates message passing and the use of the :binary option.

```elixir
iex> port = Port.open({:spawn, "cat"}, [:binary])
iex> send(port, {self(), {:command, "hello"}})
iex> send(port, {self(), {:command, "world"}})
iex> flush()
{#Port<0.1444>, {:data, "hello"}}
{#Port<0.1444>, {:data, "world"}}
iex> send(port, {self(), :close})
:ok
iex> flush()
{#Port<0.1444>, :closed}
:ok
```

--------------------------------

### utc_now/0 examples

Source: https://elixir.hexdocs.pm/NaiveDateTime.md

Examples of getting the current naive datetime in UTC, with and without truncation to seconds.

```elixir
iex> naive_datetime = NaiveDateTime.utc_now()
iex> naive_datetime.year >= 2016
true
```

```elixir
iex> naive_datetime = NaiveDateTime.utc_now(:second)
iex> naive_datetime.microsecond
{0, 0}
```

--------------------------------

### File.mkdir_p!/1 examples

Source: https://elixir.hexdocs.pm/File.html

Examples showing successful creation and a raised File.Error when the directory cannot be created.

```elixir
File.mkdir_p!("non/existing/parents")
#=> :ok

File.mkdir_p!("/usr/sbin/temp")
** (File.Error) could not make directory (with -p) "/usr/sbin/temp": not owner
```

--------------------------------

### init/2 example

Source: https://elixir.hexdocs.pm/Supervisor.html

Example of using Supervisor.init/2 in a module-based supervisor's init/1 callback with a single child and :one_for_one strategy.

```elixir
def init(_init_arg) do
  children = [
    {Counter, 0}
  ]

  Supervisor.init(children, strategy: :one_for_one)
end
```

--------------------------------

### NaiveDateTime.local_now/1 example

Source: https://elixir.hexdocs.pm/NaiveDateTime.html

Example of using local_now/1 to get the current local time and checking its year.

```elixir
iex> naive_datetime = NaiveDateTime.local_now()
iex> naive_datetime.year >= 2019
true
```

--------------------------------

### binary_slice/3 examples: basic slicing, negative start, zero size, and out-of-range start

Source: https://elixir.hexdocs.pm/Kernel.html

These iex examples demonstrate binary_slice/3 behavior: basic slicing with clipping when start+size exceeds the binary size, negative start normalization and clamping, zero size returning an empty binary, and start beyond the binary size returning an empty binary.

```elixir
iex> binary_slice("elixir", 0, 6)
"elixir"
iex> binary_slice("elixir", 0, 5)
"elixi"
iex> binary_slice("elixir", 1, 4)
"lixi"
iex> binary_slice("elixir", 0, 10)
"elixir"
```

```elixir
iex> binary_slice("elixir", -3, 10)
"xir"
iex> binary_slice("elixir", -10, 10)
"elixir"
```

```elixir
iex> binary_slice("elixir", 1, 0)
""
```

```elixir
iex> binary_slice("elixir", 10, 10)
""
```

--------------------------------

### Enum.reduce/3 examples

Source: https://elixir.hexdocs.pm/Enum.md

Examples of using Enum.reduce/3 with a list and a map. The first example sums a list starting from 0; the second sums the values of a map.

```elixir
iex> Enum.reduce([1, 2, 3], 0, fn x, acc -> x + acc end)
6
```

```elixir
iex> Enum.reduce(%{a: 2, b: 3, c: 4}, 0, fn {_key, val}, acc -> acc + val end)
9
```

--------------------------------

### format/2 example

Source: https://elixir.hexdocs.pm/Inspect.Algebra.html

Example showing how to format a document with a width of 30 and 10, producing "hello world" and "hello\nworld" respectively.

```elixir
iex> doc = Inspect.Algebra.glue("hello", " ", "world")
iex> doc = Inspect.Algebra.group(doc)
iex> doc |> Inspect.Algebra.format(30) |> IO.iodata_to_binary()
"hello world"
iex> doc |> Inspect.Algebra.format(10) |> IO.iodata_to_binary()
"hello\nworld"
```

--------------------------------

### with_index with offset example

Source: https://elixir.hexdocs.pm/Stream.md

Example showing Stream.with_index/2 with an integer offset, starting indexing from the given offset.

```elixir
iex> stream = Stream.with_index([1, 2, 3], 3)
iex> Enum.to_list(stream)
[{1, 3}, {2, 4}, {3, 5}]
```

--------------------------------

### Start DynamicSupervisor and add child

Source: https://elixir.hexdocs.pm/dynamic-supervisor.md

Demonstrates starting a DynamicSupervisor with strategy :one_for_one and adding a child process (KV.Bucket) using DynamicSupervisor.start_child. Shows basic usage in IEx.

```elixir
iex> {:ok, sup_pid} = DynamicSupervisor.start_link(strategy: :one_for_one)
iex> DynamicSupervisor.start_child(sup_pid, {KV.Bucket, name: :another_list})
iex> KV.Bucket.put(:another_list, "milk", 1)
:ok
iex> KV.Bucket.get(:another_list, "milk")
1
```

--------------------------------

### Macro.Env.expand_alias/4 error example

Source: https://elixir.hexdocs.pm/Macro.Env.html

Interactive example showing that :error is returned when there is no alias or the alias starts with Elixir.

```elixir
iex> alias List, as: MyList
iex> Macro.Env.expand_alias(__ENV__, [], [:Elixir, MyList])
:error
iex> Macro.Env.expand_alias(__ENV__, [], [:AnotherList])
:error

```

--------------------------------

### Start an application manually with Application.ensure_all_started/1

Source: https://elixir.hexdocs.pm/Application.html

Starts an application and all its dependencies. Returns {:ok, pid} or {:ok, pid, state} on success.

```elixir
{:ok, _} = Application.ensure_all_started(:some_app)
```

--------------------------------

### System.build_info/0 example output

Source: https://elixir.hexdocs.pm/System.md

Example output of System.build_info/0 in an IEx session, showing the returned map with build, date, otp_release, revision, and version fields.

```elixir
iex> System.build_info()
%{
  build: "1.9.0-dev (772a00a0c) (compiled with Erlang/OTP 21)",
  date: "2018-12-24T01:09:21Z",
  otp_release: "21",
  revision: "772a00a0c",
  version: "1.9.0-dev"
}
```

--------------------------------

### spawn/3 examples with :monitor and :link options

Source: https://elixir.hexdocs.pm/Process.md

Examples of Process.spawn/3 with :monitor and :link options. The :monitor option returns a tuple with PID and reference, while :link returns just the PID.

```elixir
Process.spawn(fn -> 1 + 2 end, [:monitor])
#=> {#PID<0.93.0>, #Reference<0.18808174.1939079169.202418>}
Process.spawn(fn -> 1 + 2 end, [:link])
#=> #PID<0.95.0>
```

--------------------------------

### module_info/1 example with URI

Source: https://elixir.hexdocs.pm/Module.html

Example showing how to use module_info/1 to get the module itself and check if a function is exported.

```elixir
iex> URI.module_info(:module)
URI
iex> {:decode_www_form, 1} in URI.module_info(:exports)
true
```

--------------------------------

### lstat examples

Source: https://elixir.hexdocs.pm/File.md

Examples of using File.lstat to get file information, showing symlink and error cases.

```elixir
File.lstat("link_to_hello")
#=> {:ok, %File.Stat{type: :symlink, ...}}
```

```elixir
File.lstat("non_existing.txt", time: :posix)
#=> {:error, :enoent}
```

--------------------------------

### Examples for Access.get/3

Source: https://elixir.hexdocs.pm/Access.html

IEx session examples demonstrating Access.get/3 with maps and keyword lists, including default values.

```elixir
iex> Access.get(%{name: "john"}, :name, "default name")
"john"
iex> Access.get(%{name: "john"}, :age, 25)
25

iex> Access.get([ordered: true], :timeout)
nil
```

--------------------------------

### get/3 examples

Source: https://elixir.hexdocs.pm/Keyword.html

IEx examples for get/3, demonstrating retrieval of existing and missing keys, default values, and behavior with duplicate keys.

```elixir
iex> Keyword.get([], :a)
nil
iex> Keyword.get([a: 1], :a)
1
iex> Keyword.get([a: 1], :b)
nil
iex> Keyword.get([a: 1], :b, 3)
3
```

```elixir
iex> Keyword.get([a: 1, a: 2], :a, 3)
1
iex> Keyword.get([a: 1, a: 2], :b, 3)
3
```

--------------------------------

### NaiveDateTime.utc_now/1 examples

Source: https://elixir.hexdocs.pm/NaiveDateTime.html

Examples of getting the current UTC naive datetime and truncating it to seconds. The second example shows that the microsecond field becomes {0, 0}.

```elixir
iex> naive_datetime = NaiveDateTime.utc_now()
iex> naive_datetime.year >= 2016
true

iex> naive_datetime = NaiveDateTime.utc_now(:second)
iex> naive_datetime.microsecond
{0, 0}
```

--------------------------------

### Code.require_file/2 example - first require

Source: https://elixir.hexdocs.pm/Code.html

Example showing that when the file has not been required, Code.require_file/2 returns a list of modules. The example uses List.first/1 to get the first module.

```elixir
modules = Code.require_file("eex_test.exs", "../eex/test")
List.first(modules)
#=> {EExTest.Compiled, <<70, 79, 82, 49, ...>>}
```

--------------------------------

### Start PartitionSupervisor with DynamicSupervisor

Source: https://elixir.hexdocs.pm/DynamicSupervisor.html

Shows how to start a PartitionSupervisor that will start a DynamicSupervisor for each core.

```elixir
children = [
  {PartitionSupervisor,
   child_spec: DynamicSupervisor,
   name: MyApp.DynamicSupervisors}
]
```

--------------------------------

### append_path/2 examples

Source: https://elixir.hexdocs.pm/URI.html

Examples of using URI.append_path/2, including a successful case and an error case when the path does not start with a slash.

```elixir
iex> URI.append_path(URI.parse("http://example.com/foo/?x=1"), "/my-path") |> URI.to_string()
"http://example.com/foo/my-path?x=1"
```

```elixir
iex> URI.append_path(URI.parse("http://example.com"), "my-path")
** (ArgumentError) path must start with "/", got: "my-path"
```

--------------------------------

### System.cmd/3 basic example

Source: https://elixir.hexdocs.pm/System.md

Runs the echo command with the argument "hello" and returns the output and exit status.

```elixir
iex> System.cmd("echo", ["hello"])
{"hello\n", 0}
```

--------------------------------

### String.slice/3 with start beyond length

Source: https://elixir.hexdocs.pm/String.html

Example showing that when start is greater than the string length, an empty string is returned.

```elixir
iex> String.slice("elixir", 10, 1500)
""
```

--------------------------------

### init/1 example

Source: https://elixir.hexdocs.pm/DynamicSupervisor.html

Example of using DynamicSupervisor.init/1 in a module-based supervisor's init/1 callback, setting max_children to 1000.

```elixir
def init(_arg) do
  DynamicSupervisor.init(max_children: 1000)
end
```

--------------------------------

### File.open/2 example

Source: https://elixir.hexdocs.pm/File.html

Example showing how to open a gzip-compressed file for reading and read a line.

```elixir
{:ok, file} = File.open("foo.tar.gz", [:read, :compressed])
IO.read(file, :line)
File.close(file)
```

--------------------------------

### get_and_update_in/2 macro example

Source: https://elixir.hexdocs.pm/Kernel.html

Example of using get_and_update_in/2 with a bracket path to get and update a nested value in a map.

```elixir
get_and_update_in(opts[:foo][:bar], &{&1, &1 + 1})
```

--------------------------------

### elem/3 examples

Source: https://elixir.hexdocs.pm/Kernel.html

Examples of using elem/3 to get elements from a tuple, including error cases for invalid indices.

```elixir
iex> tuple = {:foo, :bar, 3}
iex> elem(tuple, 1)
:bar

elem({}, 0)
** (ArgumentError) argument error

elem({:foo, :bar}, 2)
** (ArgumentError) argument error
```

--------------------------------

### Example of reading configuration with get_env/3

Source: https://elixir.hexdocs.pm/Application.html

Example showing how to retrieve a database configuration using Application.get_env/3 and access the :ip key.

```elixir
config = Application.get_env(:my_app, Databases.RepoOne)
config[:ip]
```

--------------------------------

### start_link/1

Source: https://elixir.hexdocs.pm/PartitionSupervisor.html

Starts a partition supervisor with the given options.

```APIDOC
## start_link(opts)

### Description
Starts a partition supervisor with the given options.

### Function
start_link(opts)

### Parameters
- **opts** (start_link_option()) - The options to start the supervisor.

### Returns
{:ok, pid} or {:error, reason}.
```

--------------------------------

### Function.info/2 examples with named function

Source: https://elixir.hexdocs.pm/Function.md

Examples of using Function.info/2 with a named function to get :name and :pid information.

```elixir
iex> fun = &String.length/1
iex> Function.info(fun, :name)
{:name, :length}
iex> Function.info(fun, :pid)
{:pid, :undefined}
```

--------------------------------

### Function.info/2 examples with anonymous function

Source: https://elixir.hexdocs.pm/Function.md

Examples of using Function.info/2 with an anonymous function to get :arity and :type information.

```elixir
iex> f = fn x -> x end
iex> Function.info(f, :arity)
{:arity, 1}
iex> Function.info(f, :type)
{:type, :local}
```

--------------------------------

### KV module with DynamicSupervisor and Registry

Source: https://elixir.hexdocs.pm/dynamic-supervisor.md

Complete module example showing how to start a DynamicSupervisor in the application supervision tree, create buckets dynamically, and look them up using a Registry.

```elixir
defmodule KV do
  use Application

  @impl true
  def start(_type, _args) do
    children = [
      {Registry, name: KV, keys: :unique},
      {DynamicSupervisor, name: KV.BucketSupervisor, strategy: :one_for_one}
    ]

    Supervisor.start_link(children, strategy: :one_for_one)
  end

  @doc """
  Creates a bucket with the given name.
  """
  def create_bucket(name) do
    DynamicSupervisor.start_child(KV.BucketSupervisor, {KV.Bucket, name: via(name)})
  end

  @doc """
  Looks up the given bucket.
  """
  def lookup_bucket(name) do
    GenServer.whereis(via(name))
  end

  defp via(name), do: {:via, Registry, {KV, name}}
end
```

--------------------------------

### fetch/2 examples

Source: https://elixir.hexdocs.pm/Access.html

Examples showing Access.fetch/2 returning {:ok, "meg"} for an existing key and :error for a missing key.

```elixir
iex> Access.fetch(%{name: "meg", age: 26}, :name)
{:ok, "meg"}

iex> Access.fetch([ordered: true, on_timeout: :exit], :timeout)
:error
```

--------------------------------

### File.mkdir_p/1 examples

Source: https://elixir.hexdocs.pm/File.html

Examples showing successful creation of nested directories and a failure due to permissions (eperm).

```elixir
File.mkdir_p("non/existing/parents")
#=> :ok

File.mkdir_p("/usr/sbin/temp")
#=> {:error, :eperm}
```

--------------------------------

### System.restart/0 example

Source: https://elixir.hexdocs.pm/System.html

Example call to System.restart/0, which smoothly takes down all applications, unloads code, closes ports, and starts all applications again.

```elixir
System.restart()
```

--------------------------------

### Start release node with NODES, PORT, and RELEASE_NODE

Source: https://elixir.hexdocs.pm/releases.html

Starts the release with the node name 'foo' and port 4040. Requires adjusting @computer-name to the actual computer name.

```shell
$ NODES="foo@computer-name,bar@computer-name" PORT=4040 RELEASE_NODE="foo" bin/kv start_iex
```

```shell
$ NODES="foo@computer-name,bar@computer-name" PORT=4041 RELEASE_NODE="bar" bin/kv start_iex
```

--------------------------------

### overridables_in/1 example

Source: https://elixir.hexdocs.pm/Module.html

Example showing how to use Module.overridables_in/1 to get sorted overridable definitions. The module must not be compiled yet.

```elixir
defmodule Example do
  def foo, do: 1
  def bar, do: 2

  defoverridable foo: 0, bar: 0
  def foo, do: 3

  [bar: 0, foo: 0] = Module.overridables_in(__MODULE__) |> Enum.sort()
end
```

--------------------------------

### mkdir examples

Source: https://elixir.hexdocs.pm/File.md

Examples showing mkdir returning :ok for a successful creation and {:error, :enoent} when a parent directory is missing.

```elixir
File.mkdir("test/unit")
#=> :ok
```

```elixir
File.mkdir("non/existing")
#=> {:error, :enoent}
```

--------------------------------

### URI.parse/1 protocol-relative URL example

Source: https://elixir.hexdocs.pm/URI.html

Example of URI.parse/1 with a protocol-relative URL (starting with //), showing scheme nil and port nil.

```elixir
iex> URI.parse("//elixir-lang.org/")
%URI{
  authority: "elixir-lang.org",
  fragment: nil,
  host: "elixir-lang.org",
  path: "/",
  port: nil,
  query: nil,
  scheme: nil,
  userinfo: nil
}
```

--------------------------------

### Example command sequence and output

Source: https://elixir.hexdocs.pm/docs-tests-and-with.html

Shows the expected interaction with the server: commands like CREATE, PUT, GET, DELETE and their responses. Used as the specification for the parser to implement.

```text
CREATE shopping
OK

PUT shopping milk 1
OK

PUT shopping eggs 3
OK

GET shopping milk
1
OK

DELETE shopping eggs
OK
```