Read an Environment Variable using the Standard Library

Task

Operating System / Read an Environment Variable

No packages used

This recipe uses only the OCaml Standard Library.

Code
(* Both `Sys.getenv` and `Sys.getenv_opt` are functions that take the name of an environment and read its value. `Sys.getenv` returns the value directly, but raises a `Not_found` exception if the variable doesn't exist. ) let () = try let path = Sys.getenv "PATH" in Printf.printf "The path is %s\n" path with Not_found -> print_string "The path is not set.\n" ( In contrast, `Sys.getenv_opt` returns a value of type `string option`: `Some value` if the variable exists and `None` if it doesn't. *) let () = match Sys.getenv_opt "API_KEY" with | Some p -> Printf.printf "Api key is %s\n" p | None -> print_string "Api key is not set.\n"

Both Sys.getenv and Sys.getenv_opt are functions that take the name of an environment and read its value.

Sys.getenv returns the value directly, but raises a Not_found exception if the variable doesn't exist.

let () =
  try
    let path = Sys.getenv "PATH" in
    Printf.printf "The path is %s\n" path
  with Not_found ->
    print_string "The path is not set.\n"

In contrast, Sys.getenv_opt returns a value of type string option: Some value if the variable exists and None if it doesn't.

let () =
  match Sys.getenv_opt "API_KEY" with
  | Some p ->
      Printf.printf "Api key is %s\n" p
  | None ->
      print_string "Api key is not set.\n"

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