1 files changed, 45 insertions, 0 deletions
diff --git a/src/gleam/os.gleam b/src/gleam/os.gleam
new file mode 100644
index 0000000..c5a8c5a
--- /dev/null
+++ b/src/gleam/os.gleam
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+//// Function to interact with the host operating system.
+
+import gleam/list
+import gleam/string
+
+// Internal type for erlang interop.
+external type CharList
+
+external fn os_getenv() -> List(CharList) =
+  "os" "getenv"
+
+external fn os_putenv(key: CharList, value: CharList) -> Bool =
+  "os" "putenv"
+
+external fn os_unsetenv(key: CharList) -> Bool =
+  "os" "unsetenv"
+
+external fn char_list_to_string(CharList) -> String =
+  "erlang" "list_to_binary"
+
+external fn string_to_char_list(String) -> CharList =
+  "erlang" "binary_to_list"
+
+/// Return all environment variables set on the system.
+pub fn get_env() -> List(tuple(String, String)) {
+  list.map(
+    os_getenv(),
+    fn(char_list) {
+      assert Ok(value) = string.split_once(char_list_to_string(char_list), "=")
+      value
+    },
+  )
+}
+
+/// Set an environment variable.
+pub fn put_env(key: String, value: String) -> Nil {
+  let True = os_putenv(string_to_char_list(key), string_to_char_list(value))
+  Nil
+}
+
+/// Delete an environment variable.
+pub fn delete_env(key: String) -> Nil {
+  let True = os_unsetenv(string_to_char_list(key))
+  Nil
+}