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shellelixirescapingnewlinebackslash

System.get_env in elixir and new line (\n)

~ ❯ export TEST_KEY='hello\nworld' && iex

iex(1)> System.get_env("TEST_KEY")
"hello\\nworld"

When running System.get_env/1 on a string with \n it inserts an extra backslash, any way of preventing this behaviour?

Solution

  • It does not insert anything, it fairly reads the environment variable and, because backslashes are to be escaped in double-quotes, prints it as you see.

    What you think is “new line” is nothing but the escape sequence. Here is an excerpts from e. g. echo man:

      -e     enable interpretation of backslash escapes
  -E     disable interpretation of backslash escapes

    The default behaviour in raw shell:

    ❯ echo -E 'hello\nworld'
hello\nworld

    The fact, that you see a new line there in echo by default, or whatever is a side effect by the interpreter, whoever this interpreter is. The value itself contains a backslash and n ASCII symbols, and no magic besides.

    That said, if one wants to have new lines in place of \n sequence in the value, one must apply the escaping themselves.

    "TEST_KEY"
|> System.get_env()
|> to_string() # to NOT raise on absent value, redundant
|> String.replace("\\n", "\n")