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| IEx |
IEx (Interactive Elixir Mode)
iex is interactive Elixir. It is a command-line interface to Elixir or your Elixir application.
iex is 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.
Getting started
With Elixir installed, you should be able to simply run iex from your shell and find something like the following:
$ iex
Erlang/OTP 21 [erts-10.1.1] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [hipe] [dtrace]
Interactive Elixir (1.7.3) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)>
Now you can evaluate any valid Elixir statement followed by pressing ENTER and the result will be displayed on the next line.
iex(1) 1 + 1
2
Tab completion
iex features tab completion. Aside from saving keystrokes, it allows you to see which functions and submodules are available.
For example, type DaTAB. It should expand to Date. Now press TAB again and you'll see two options: Date and DateTime as both modules start with Date.
Now let's say you want to use a function in the Date module but can't remember the name or arity. Type a . after the module name, press TAB and you'll see all available functions in the module.
iex(3)> Date.
Range add/2 compare/2
convert!/2 convert/2 day_of_week/1
days_in_month/1 diff/2 from_erl!/1
from_erl!/2 from_erl/1 from_erl/2
from_iso8601!/1 from_iso8601!/2 from_iso8601/1
from_iso8601/2 leap_year?/1 months_in_year/1
new/3 new/4 range/2
to_erl/1 to_iso8601/1 to_iso8601/2
to_string/1 utc_today/0 utc_today/1
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.
Exiting
To exit iex, press CTRL+C to bring up the break menu. You can press a, ENTER or just press CTRL+C a second time to exit.
Cancelling statement evaluation
If you're writing a complex statement and make a mistake, you may be tempted to press CTRL+C 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.
iex allows a magic comment of #iex:break to be typed any time, followed by ENTER to abort statement evaluation.
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 ENTER:
iex(1)> %{ user: "tom, roles: ["admin", "manager"] }
...(1)> #iex:break
** (TokenMissingError) iex:1: incomplete expression
iex(1)>
Loading your Mix application
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.
$ iex -S mix