86 lines
3.5 KiB
Markdown
86 lines
3.5 KiB
Markdown
---
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title: IEx
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---
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## IEx (Interactive Elixir Mode)
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`iex` is *interactive Elixir*. It is a command-line interface to Elixir or your Elixir application.
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`iex` is [REPL][REPL] that allows you to evaluate any statement with immediate feedback. There's no need for compiling any code or putting your code into a script file.
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### Getting started
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With Elixir installed, you should be able to simply run `iex` from your shell and find something like the following:
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```shell
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$ iex
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Erlang/OTP 21 [erts-10.1.1] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [hipe] [dtrace]
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Interactive Elixir (1.7.3) - press Ctrl+C to exit (type h() ENTER for help)
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iex(1)>
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```
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Now you can evaluate any valid Elixir statement followed by pressing <kbd>ENTER</kbd> and the result will be displayed on the next line.
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```shell
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iex(1) 1 + 1
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2
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```
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### Tab completion
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`iex` features tab completion. Aside from saving keystrokes, it allows you to see which functions and submodules are available.
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For example, type <kbd>Da</kbd><kbd>TAB</kbd>. It should expand to `Date`. Now press <kbd>TAB<kbd> again and you'll see two options: `Date` and `DateTime` as both modules start with `Date`.
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Now let's say you want to use a function in the `Date` module but can't remember the name or arity. Type a <kbd>.</kbd> after the module name, press <kbd>TAB</kbd> and you'll see all available functions in the module.
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```shell
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iex(3)> Date.
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Range add/2 compare/2
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convert!/2 convert/2 day_of_week/1
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days_in_month/1 diff/2 from_erl!/1
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from_erl!/2 from_erl/1 from_erl/2
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from_iso8601!/1 from_iso8601!/2 from_iso8601/1
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from_iso8601/2 leap_year?/1 months_in_year/1
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new/3 new/4 range/2
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to_erl/1 to_iso8601/1 to_iso8601/2
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to_string/1 utc_today/0 utc_today/1
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```
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You'll notice that `Range` at the top of the list. This is a submodule of `Date`. You can continue tab completion with submodules or functions.
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### Exiting
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To exit `iex`, press <kbd>CTRL</kbd>+<kbd>C</kbd> to bring up the break menu. You can press <kbd>a</kbd>, <kbd>ENTER</kbd> or just press <kbd>CTRL</kbd>+<kbd>C</kbd> a second time to exit.
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### Cancelling statement evaluation
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If you're writing a complex statement and make a mistake, you may be tempted to press <kbd>CTRL</kbd>+<kbd>C</kbd> to cancel statement evaluation as you would in a standard shell. Unfortunately that won't work in `iex` as it just brings up the break menu.
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`iex` allows a magic comment of `#iex:break` to be typed any time, followed by <kbd>ENTER</kbd> to abort statement evaluation.
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Let's take this example where you are constructing a map and forgot a quote partway through. You pressed enter to evaluate and get stuck at a statement continuation prompt and you want to abort. Just type `#iex:break` followed by <kbd>ENTER</kbd>:
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```shell
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iex(1)> %{ user: "tom, roles: ["admin", "manager"] }
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...(1)> #iex:break
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** (TokenMissingError) iex:1: incomplete expression
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iex(1)>
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```
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### Loading your Mix application
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`iex` can load a script during startup. A common use for this is loading your `mix.exs` script so that your `iex` session contains your whole application and its dependencies loaded and ready to work with.
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```shell
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$ iex -S mix
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```
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#### More Information:
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* [Official Elixir Documentation](https://elixir-lang.org/getting-started/introduction.html#interactive-mode)
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[REPL]: https://en.wikipedia.org/wiki/Read%E2%80%93eval%E2%80%93print_loop
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