How do I save IEx history?

I don't know if things changed at some point, but I found the above did not work. After looking at the man page for iex, I noticed that it needed to be

export ELIXIR_ERL_OPTIONS="-kernel shell_history enabled"

(note the additional ELIXIR). Perhaps the original solution was cogent was relevant for erl (I found it worked for that), but iex added the qualifier? Since the original question was for iex though, figured it should be updated.

For Erlang/OTP 20

This is built-in (from https://hexdocs.pm/iex/IEx.html#module-shell-history)

From Erlang/OTP 20, it is possible to get shell history by passing some flags that enable it in the VM. This can be done on a per-need basis when starting IEx:

iex --erl "-kernel shell_history enabled"

If you would rather enable it on your system as a whole, you can use the ERL_AFLAGS environment variable and make sure that it is set accordingly on your terminal/shell configuration.

On Linux [and macOS]:

export ERL_AFLAGS="-kernel shell_history enabled"

On Windows:

set ERL_AFLAGS "-kernel shell_history enabled"

To show where the history file is located, run the following code from erl (Mac OS example value shown):

1> filename:basedir(user_cache, "erlang-history")
"/Users/your.username/Library/Caches/erlang-history"

To set the file to a different location, use the shell_history_path /path/to/history-file option from the erlang docs (compatible with Elixir/iex):

export ERL_AFLAGS="-kernel shell_history_path '\"$HOME/.erlang-history\"'"

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For Erlang/OTP 19 and below

Try using https://github.com/ferd/erlang-history

> git clone https://github.com/ferd/erlang-history.git
> cd erlang-history
> sudo make install    # may not need sudo depending on installation

I'm using the oh-my-zsh, so I put on the vim ~/.zshrc:

# Enable history in IEX through Erlang(OTP)
export ERL_AFLAGS="-kernel shell_history enabled"

then source ~/.zshrc and now always load. Thank's @loeschg.