Read environment variables

Addresses #15

README.md

@@ -7,6 +7,7 @@ Examples showing how to do many things in Gleam!
 - [Data structures](#data-structures)
 - [File system](#file-system)
 - [Formats](#formats)
+- [Operating system](#operating-system)
 
 ## Algorithms
 
@@ -31,3 +32,7 @@ Examples showing how to do many things in Gleam!
 - [Rendering HTML](./universal/test/formats/rendering_html.gleam)
 - [Rendering JSON](./universal/test/formats/rendering_json.gleam)
 - [Rendering XML](./universal/test/formats/rendering_xml.gleam)
+
+## Operating system
+
+- [Read environment variables](./universal/test/operating_system/read_environment_variables.gleam)

universal/gleam.toml

@@ -21,6 +21,7 @@ gleam_json = ">= 1.0.1 and < 2.0.0"
 lustre = ">= 4.4.4 and < 5.0.0"
 gleam_crypto = ">= 1.3.0 and < 2.0.0"
 tom = ">= 1.1.0 and < 2.0.0"
+envoy = ">= 1.0.1 and < 2.0.0"
 
 [dev-dependencies]
 gleeunit = ">= 1.0.0 and < 2.0.0"

universal/manifest.toml

@@ -2,6 +2,7 @@
 # You typically do not need to edit this file
 
 packages = [
+  { name = "envoy", version = "1.0.1", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "envoy", source = "hex", outer_checksum = "CFAACCCFC47654F7E8B75E614746ED924C65BD08B1DE21101548AC314A8B6A41" },
   { name = "filepath", version = "1.0.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "filepath", source = "hex", outer_checksum = "EFB6FF65C98B2A16378ABC3EE2B14124168C0CE5201553DE652E2644DCFDB594" },
   { name = "gleam_crypto", version = "1.3.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_crypto", source = "hex", outer_checksum = "ADD058DEDE8F0341F1ADE3AAC492A224F15700829D9A3A3F9ADF370F875C51B7" },
   { name = "gleam_erlang", version = "0.26.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_erlang", source = "hex", outer_checksum = "3DF72F95F4716883FA51396FB0C550ED3D55195B541568CAF09745984FD37AD1" },
@@ -17,6 +18,7 @@ packages = [
 ]
 
 [requirements]
+envoy = { version = ">= 1.0.1 and < 2.0.0" }
 gleam_crypto = { version = ">= 1.3.0 and < 2.0.0" }
 gleam_json = { version = ">= 1.0.1 and < 2.0.0" }
 gleam_stdlib = { version = ">= 0.34.0 and < 2.0.0" }

universal/test/operating_system/read_environment_variables.gleam

@@ -0,0 +1,36 @@
+//// # Read environment variables
+//// 
+//// The envoy package is used to work with environment variables. This package
+//// works on both Erlang and JavaScript targets.
+//// 
+//// ## Dependencies
+//// 
+//// - https://hex.pm/packages/envoy
+
+import envoy
+import gleam/dict
+
+pub fn main_test() {
+  // The `unset` function can be used to unset environment variables. We are
+  // using it first here to reset the PORT environment variable to a known
+  // state.
+  envoy.unset("PORT")
+
+  // We've used `let assert` to crash if any of these functions fail. In a real
+  // application or library you'd want to handle the results properly.
+
+  // The `get` function gets environment variables by name. It returns an error
+  // if the environment variable is not set.
+  let assert Error(Nil) = envoy.get("PORT")
+
+  // The `set` function sets environment variables.
+  envoy.set("PORT", "8080")
+
+  // The `get` function returns `Ok` if the environment variable is set.
+  let assert Ok("8080") = envoy.get("PORT")
+
+  // The `all` function can be used to get a Dict of all set environment
+  // variables.
+  let environment_variables = envoy.all()
+  let assert Ok("8080") = dict.get(environment_variables, "PORT")
+}