ffenv

func Parse ¶

func Parse(r io.Reader, set func(name, value string) error) error

Parse is a parser for .env files.

Each line in the .env file is tokenized on the first `=` character. The first token is interpreted as the env var representation of the flag name, and the second token is interpreted as the value. Both tokens are trimmed of leading and trailing whitespace. If the value is "double quoted", control characters like `\n` are expanded. Lines beginning with `#` are interpreted as comments. End-of-line comments are not supported.

Parse options related to environment variables, like [ff.WithEnvVarPrefix], [ff.WithEnvVarShortNames], and [ff.WithEnvVarCaseSensitive], also apply to .env files. For example, WithEnvVarPrefix("MYPROG") means that the keys in an .env file must begin with MYPROG_.

If for any reason any key in an .env file matches multiple flags, parse will return [ff.ErrDuplicateFlag]. This can happen if you have flags with names that differ only in capitalization, e.g. `-v` and `-V`. If you want to support setting these flags from an .env file, either use discrete long names, or [ff.WithEnvVarCaseSensitive].

Using the .env config file parser doesn't automatically enable parsing of actual environment variables. To do so, callers must still explicitly provide e.g. [ff.WithEnvVars] or [ff.WithEnvVarPrefix].