Source file timedesc_tzlocal.ml

let local () : string list =
  (* Approached copied from Python package tzlocal:
     https://github.com/regebro/tzlocal
  *)
  match Sys.getenv_opt "TZ" with
  | Some name -> [ name ]
  | None -> (
      if CCIO.File.exists "/system/bin/getprop" then (
        (* if we are under Termux on Android *)
        let ic = Unix.open_process_in "getprop" in
        let name = CCIO.read_all ic in
        close_in ic;
        [ name ])
      else
        (* Look for distribution specific configs *)
        let try1 =
          List.fold_left
            (fun tz file ->
              match tz with
              | Some tz -> Some tz
              | None -> (
                  try
                    CCIO.with_in ~flags:[ Open_rdonly ] file (fun ic ->
                        let lines = CCIO.read_lines_l ic in
                        match lines with
                        | [] -> None
                        | x :: _ ->
                            if CCString.sub x 0 5 = "TZif2" then None
                            else
                              List.fold_left
                                (fun tz line ->
                                  match tz with
                                  | Some tz -> Some tz
                                  | None ->
                                      let name =
                                        line
                                        |> String.split_on_char ' '
                                        |> List.hd
                                        |> String.split_on_char '#'
                                        |> List.hd
                                      in
                                      Some name)
                                None lines)
                  with _ -> None))
            None
            [ "/etc/timezone"; "/var/db/zoneinfo" ]
        in
        match try1 with
        | Some name -> [ name ]
        | None -> (
            (* CentOS has a ZONE setting in /etc/sysconfig/clock,
               OpenSUSE has a TIMEZONE setting in /etc/sysconfig/clock and
               Gentoo has a TIMEZONE setting in /etc/conf.d/clock
               We look through these files for a timezone
            *)
            let try2 =
              List.fold_left
                (fun tz file ->
                  match tz with
                  | Some tz -> Some tz
                  | None -> (
                      try
                        CCIO.with_in ~flags:[ Open_rdonly ] file (fun ic ->
                            let lines = CCIO.read_lines_l ic in
                            List.fold_left
                              (fun tz line ->
                                match tz with
                                | Some tz -> Some tz
                                | None -> (
                                    let name =
                                      try
                                        Some
                                          (Scanf.sscanf line {| ZONE = "%[^"]"|}
                                             CCFun.id)
                                      with _ -> (
                                        try
                                          Some
                                            (Scanf.sscanf line
                                               {| TIMEZONE = "%[^"]"|} CCFun.id)
                                        with _ -> None)
                                    in
                                    match name with
                                    | None -> None
                                    | Some s ->
                                        Some
                                          (CCString.replace ~sub:" " ~by:"_" s)))
                              None lines)
                      with _ -> None))
                None
                [ "/etc/sysconfig/clock"; "/etc/conf.d/clock" ]
            in
            match try2 with
            | Some name -> [ name ]
            | None ->
                (* systemd distributions use symlinks that include the zone name *)
                let try3 =
                  let file = "/etc/localtime" in
                  if FileUtil.(test Is_link file) then
                    let real_path = FileUtil.readlink file in
                    let parts = String.split_on_char '/' real_path in
                    let combinations, _ =
                      List.fold_left
                        (fun (acc, parts) _ -> (parts :: acc, List.tl parts))
                        ([], parts) parts
                    in
                    List.map (String.concat "/") combinations
                  else []
                in
                try3))