Catalin Constantin Mititiuc
449a41aa85
Update the dracula theme styles to make 'console' highlighting more legible
45 lines
1.5 KiB
Markdown
45 lines
1.5 KiB
Markdown
---
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title: "Open An IEx Shell From An Elixir Script"
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blurb: "We can run an Elixir script with either the `elixir` or the
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`iex` command. Both will execute the code, but the second command
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opens an interactive IEx shell afterward. What if, we won't know until runtime
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whether we want a shell or not? How can we start an IEx session even when we
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use `elixir`, instead of `iex`, to run our script?"
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...
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I recently had occasion to want to start an IEx session from an Elixir script. Here's how I was able to do it.
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## Method 1
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Here's a quick test script:
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<p class="code-filename-label">`run.exs`</p>
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```elixir
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:shell.start_interactive({IEx, :start, []})
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System.no_halt(true)
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```
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`System.no_halt(true)` is needed so that the interactive session doesn't die when the process running the script ends. You could also use the `elixir` command with the `--no-halt` option instead to achieve the same effect.
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When we run this script with just `elixir` (instead of `iex`), we should still see an interactive IEx session start.
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```console
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$ elixir run.exs
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Erlang/OTP 26 [erts-14.1] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [jit:ns]
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Interactive Elixir (1.15.6) - press Ctrl+C to exit (type h() ENTER for help)
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iex(1)>
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```
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## Method 2
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While researching, I found another way that works, but it's even more obscure than the above method.
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```elixir
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:user_drv.start_shell(%{initial_shell: {IEx, :start, []}})
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```
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I can't find documentation for `user_drv`, I had to browse the [code](https://github.com/erlang/otp/blob/master/lib/kernel/src/user_drv.erl) directly.
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