std.file.env#

.env files: one KEY=value line per setting, as Docker, Compose, and most web frameworks read them.

mars

takepkg std.file;
takepkg std.file.env;

func m{
    settings = env.read(file.here(".env"));
    out(settings.get("PORT"));
}

text

# .env
PORT=8080
NAME="My App"   # shown in the title
export DEBUG=true

Function	Result
`read(path)`, `parse(text)`	A map from name to value
`write(path, values)`, `format(values)`	A map as `KEY=value` lines

Reading#

Blank lines and # comments are skipped, and export before a key is allowed.
An unquoted value runs to the end of the line, or to a # after a space: URL=http://host/#top keeps its #.
A double-quoted value may span lines and takes \n, \t, \", and \\ escapes; a single-quoted one is taken exactly as written.
Every value is a string: PORT=8080 gives "8080"; convert with int().
$NAME is not expanded; it stays $NAME.
A key given twice keeps its first position and its last value.

Mistakes raise SyntaxError with the line, and the file when there is one:

text

SyntaxError: .env: env line 4: expected KEY=value
SyntaxError: env line 1: "1BAD" is not a variable name: letters, digits, and _, not starting with a digit

Writing#

Plain words are written as they are. Other values are single-quoted, which every reader takes exactly, so $ and # stay literal; a value holding a single quote or a line break is double-quoted with escapes instead. Either way it reads back the same. Numbers and booleans are written as out prints them.

Keys must be names: letters, digits, and _, not starting with a digit.

std.file.env reads and writes files; it does not change the program's environment. To read the environment itself, use std.os.

The wrapper is written in Marslang (std/file/env.mars) over the native package std/rs/config.rs.