Elixir:
Writing to standard error

How to:

In Elixir, you can use IO module functions such as IO.puts/2 and IO.warn/2 to write messages to standard error:

# Writing a simple message to stderr
IO.puts(:stderr, "Error: Something went wrong!")

# Using IO.warn, which is more semantic for warnings/errors
IO.warn("Warning: You are about to exceed the limit!")

Sample output in the terminal for IO.puts/2:

Error: Something went wrong!

For IO.warn/2, the output would be similar, but IO.warn/2 is specifically designed for warnings and might include additional formatting or behavior in future Elixir versions.

Using Third-Party Libraries

While Elixir’s standard library is usually sufficient for handling standard error output, you might find libraries like Logger useful for more complex applications or for configuring different log levels and outputs.

Example using Logger to output an error message:

require Logger

# Configure Logger to output to stderr
Logger.configure_backend(:console, device: :stderr)

# Writing an error message
Logger.error("Error: Failed to connect to the database.")

This setup directs the Logger’s output specifically to stderr, which is useful for separating error logging from standard log messages.