IO.puts vs IO.inspect

Question

It seems to me that IO.puts and IO.inspect are both used to print to the console. What is the difference between them?

Answer 1

Adding to the previous answer, IO.inspect can print an arbitrary elixir term, with an optional keyword list containing a label: and values for initializing an Inspect.Opts struct:

@spec inspect(item, Keyword.t) :: item when item: var

IO.puts requires the argument to be either a string, or a struct that implements the String.Chars protocol:

@spec puts(device, chardata | String.Chars.t) :: :ok

Answer 2

Reading through the Elixir docs, it looks like IO.puts/2 is simply going to write and append a newline.

IO.inspect/2 will do the same thing, but it also returns the first value unchanged (so it's chainable), enables pretty printing/decoration and other formatting options.

• https://hexdocs.pm/elixir/IO.html#inspect/2
• https://hexdocs.pm/elixir/IO.html#print/2

Friendly reminder that hexdocs can be really awesome. I was able to easily find the answer to your question and learn the differences myself. I highly encourage you to read through modules you normally use to discover other functions you might not know about that you could be benefitting from.