diff --git a/infer/src/IR/Io_infer.ml b/infer/src/IR/Io_infer.ml
index e2ffd4b90..c5e1242b8 100644
--- a/infer/src/IR/Io_infer.ml
+++ b/infer/src/IR/Io_infer.ml
@@ -140,8 +140,8 @@ struct
     let fd =
       Unix.openfile
         (DB.filename_to_string full_fname)
-        [Unix.O_WRONLY; Unix.O_APPEND]
-        0o777 in
+        ~mode:Unix.[O_WRONLY; O_APPEND]
+        ~perm:0o777 in
     let outc = Unix.out_channel_of_descr fd in
     let fmt = F.formatter_of_out_channel outc in
     (fd, fmt)
diff --git a/infer/src/IR/Io_infer.mli b/infer/src/IR/Io_infer.mli
index 5c723ddc8..4680454ae 100644
--- a/infer/src/IR/Io_infer.mli
+++ b/infer/src/IR/Io_infer.mli
@@ -14,11 +14,11 @@ open! Utils
 
 module Html : sig
   (** Close an Html file *)
-  val close : Unix.file_descr * Format.formatter -> unit
+  val close : Unix.File_descr.t * Format.formatter -> unit
 
   (** Create a new html file *)
   val create :
-    DB.Results_dir.path_kind -> DB.Results_dir.path -> Unix.file_descr * Format.formatter
+    DB.Results_dir.path_kind -> DB.Results_dir.path -> Unix.File_descr.t * Format.formatter
 
   (** Return true if the html file was modified since the beginning of the analysis *)
   val modified_during_analysis : SourceFile.t -> DB.Results_dir.path -> bool
@@ -27,7 +27,7 @@ module Html : sig
   val node_filename : Procname.t -> int -> string
 
   (** Open an Html file to append data *)
-  val open_out : SourceFile.t -> DB.Results_dir.path -> Unix.file_descr * Format.formatter
+  val open_out : SourceFile.t -> DB.Results_dir.path -> Unix.File_descr.t * Format.formatter
 
   (** Print an html link to the given line number of the current source file *)
   val pp_line_link :
diff --git a/infer/src/backend/PerfStats.ml b/infer/src/backend/PerfStats.ml
index 6d3be385f..abecad2e1 100644
--- a/infer/src/backend/PerfStats.ml
+++ b/infer/src/backend/PerfStats.ml
@@ -146,7 +146,7 @@ let register_report_at_exit file =
       try
         let json_stats = to_json (stats ()) in
         try
-          create_path (Filename.dirname file);
+          Unix.mkdir_p (Filename.dirname file);
           let stats_oc = open_out file in
           Yojson.Basic.pretty_to_channel stats_oc json_stats ;
           close_out stats_oc
diff --git a/infer/src/backend/infer.ml b/infer/src/backend/infer.ml
index 3b99f062d..013009ae4 100644
--- a/infer/src/backend/infer.ml
+++ b/infer/src/backend/infer.ml
@@ -76,8 +76,8 @@ let remove_results_dir () =
   rmtree Config.results_dir
 
 let create_results_dir () =
-  create_path (Config.results_dir // Config.captured_dir_name) ;
-  create_path (Config.results_dir // Config.specs_dir_name)
+  Unix.mkdir_p (Config.results_dir // Config.captured_dir_name) ;
+  Unix.mkdir_p (Config.results_dir // Config.specs_dir_name)
 
 let clean_results_dir () =
   let dirs = ["classnames"; "filelists"; "multicore"; "sources"] in
@@ -111,17 +111,16 @@ let register_perf_stats_report () =
   let stats_dir = Filename.concat Config.results_dir Config.backend_stats_dir_name in
   let stats_base = Config.perf_stats_prefix ^ ".json" in
   let stats_file = Filename.concat stats_dir stats_base in
-  create_path stats_dir;
+  Unix.mkdir_p stats_dir;
   PerfStats.register_report_at_exit stats_file
 
 
 let touch_start_file () =
   let start = Config.results_dir // Config.start_filename in
-  let file_perm = 0o0666 in
   let flags =
     Unix.O_CREAT :: Unix.O_WRONLY :: (if Config.continue_capture then [Unix.O_EXCL] else []) in
   (* create new file, or open existing file for writing to update modified timestamp *)
-  try Unix.close (Unix.openfile start flags file_perm)
+  try Unix.close (Unix.openfile ~perm:0o0666 ~mode:flags start)
   with Unix.Unix_error (Unix.EEXIST, _, _) -> ()
 
 
@@ -138,7 +137,6 @@ let run_command ~prog ~args after_wait =
 
 
 let check_xcpretty () =
-  let open! Core.Std in
   match Unix.system "xcpretty --version" with
   | Ok () -> ()
   | Error _ ->
@@ -232,7 +230,7 @@ let capture build_cmd = function
 let run_parallel_analysis () =
   let multicore_dir = Config.results_dir // Config.multicore_dir_name in
   rmtree multicore_dir ;
-  create_path multicore_dir ;
+  Unix.mkdir_p multicore_dir ;
   InferAnalyze.print_stdout_legend ();
   InferAnalyze.main (multicore_dir // "Makefile") ;
   let cwd = Unix.getcwd () in
diff --git a/infer/src/backend/mergeCapture.ml b/infer/src/backend/mergeCapture.ml
index 6ad02cffa..00118246d 100644
--- a/infer/src/backend/mergeCapture.ml
+++ b/infer/src/backend/mergeCapture.ml
@@ -83,13 +83,13 @@ let add_multilink_attr ~stats src dst =
 
 let create_link ~stats src dst =
   if link_exists dst then Unix.unlink dst;
-  Unix.symlink src dst;
+  Unix.symlink ~src ~dst;
   (* Set the accessed and modified time of the original file slightly in the past.  Due to
      the coarse precision of the timestamps, it is possible for the source and destination of a
      link to have the same modification time. When this happens, the files will be considered to
      need re-analysis every time, indefinitely. *)
   let near_past = Unix.gettimeofday () -. 1. in
-  Unix.utimes src near_past near_past;
+  Unix.utimes src ~access:near_past ~modif:near_past;
   stats.files_linked <- stats.files_linked + 1
 
 let create_multilinks () =
@@ -110,7 +110,7 @@ let rec slink ~stats ~skiplevels src dst =
   then
     begin
       if not (Sys.file_exists dst)
-      then Unix.mkdir dst 0o700;
+      then Unix.mkdir dst ~perm:0o700;
       let items = Sys.readdir src in
       Array.iter
         (fun item ->
diff --git a/infer/src/base/CommandLineOption.ml b/infer/src/base/CommandLineOption.ml
index 12a8b6152..93737cd4c 100644
--- a/infer/src/base/CommandLineOption.ml
+++ b/infer/src/base/CommandLineOption.ml
@@ -596,11 +596,11 @@ let parse ?(incomplete=false) ?(accept_unknown=false) ?config_file current_exe e
   ;
   full_speclist := add_or_suppress_help (normalize !full_desc_list)
   ;
-  let env_args = decode_env_to_argv (try Unix.getenv args_env_var with Not_found -> "") in
+  let env_args = decode_env_to_argv (try Sys.getenv args_env_var with Not_found -> "") in
   (* begin transitional support for INFERCLANG_ARGS *)
   let c_args =
     Str.split (Str.regexp_string (String.make 1 ':'))
-      (try Unix.getenv "INFERCLANG_ARGS" with Not_found -> "") in
+      (try Sys.getenv "INFERCLANG_ARGS" with Not_found -> "") in
   let env_args = c_args @ env_args in
   (* end transitional support for INFERCLANG_ARGS *)
   let exe_name = Sys.executable_name in
@@ -636,6 +636,7 @@ let parse ?(incomplete=false) ?(accept_unknown=false) ?config_file current_exe e
   in
   parse_loop ();
   if not incomplete then
-    Unix.putenv args_env_var
-      (encode_argv_to_env (prefix_before_rest (IList.tl (Array.to_list !args_to_parse)))) ;
+    Unix.putenv
+      ~key:args_env_var
+      ~data:(encode_argv_to_env (prefix_before_rest (IList.tl (Array.to_list !args_to_parse)))) ;
   curr_usage
diff --git a/infer/src/base/Config.ml b/infer/src/base/Config.ml
index 08ca4cb63..84a261942 100644
--- a/infer/src/base/Config.ml
+++ b/infer/src/base/Config.ml
@@ -400,7 +400,7 @@ let init_work_dir, is_originator =
       (* Approach is borrowed from llvm implementation of *)
       (* llvm::sys::fs::current_path (implemented in Path.inc file) *)
       try
-        let pwd = Unix.getenv "PWD" in
+        let pwd = Sys.getenv "PWD" in
         let pwd_stat = Unix.stat pwd in
         let dot_stat = Unix.stat "." in
         if pwd_stat.st_dev = dot_stat.st_dev && pwd_stat.st_ino = dot_stat.st_ino then
@@ -410,7 +410,7 @@ let init_work_dir, is_originator =
       with _ ->
         Sys.getcwd () in
     let real_cwd = realpath cwd in
-    Unix.putenv "INFER_CWD" real_cwd;
+    Unix.putenv ~key:"INFER_CWD" ~data:real_cwd;
     (real_cwd, true)
 
 (** Resolve relative paths passed as command line options, i.e., with respect to the working
@@ -1648,7 +1648,7 @@ let specs_library =
         let key_dir = cache_dir // key in
         let extract_specs dest_dir filename =
           if Filename.check_suffix filename ".jar" then
-            match (Unix.mkdir dest_dir 0o700) with
+            match (Unix.mkdir dest_dir ~perm:0o700) with
             | exception Unix.Unix_error _ ->
                 ()
             | () ->
diff --git a/infer/src/base/DB.ml b/infer/src/base/DB.ml
index 23f88ca00..bdac34a84 100644
--- a/infer/src/base/DB.ml
+++ b/infer/src/base/DB.ml
@@ -14,8 +14,6 @@ open! Utils
 
 module F = Format
 module L = Logging
-module Unix = Core.Std.Unix
-module In_channel = Core.Std.In_channel
 
 (** {2 Source Dirs} *)
 
diff --git a/infer/src/base/DB.mli b/infer/src/base/DB.mli
index 76545393c..e66338b22 100644
--- a/infer/src/base/DB.mli
+++ b/infer/src/base/DB.mli
@@ -66,7 +66,7 @@ module Results_dir : sig
   val clean_specs_dir : unit -> unit
 
   (** create a file at the given path, creating any missing directories *)
-  val create_file : path_kind -> path -> Unix.file_descr
+  val create_file : path_kind -> path -> Unix.File_descr.t
 end
 
 (** origin of a analysis artifact: current results dir, a spec library, or models *)
diff --git a/infer/src/base/Logging.ml b/infer/src/base/Logging.ml
index 368c0c550..98fa067c2 100644
--- a/infer/src/base/Logging.ml
+++ b/infer/src/base/Logging.ml
@@ -46,13 +46,13 @@ let set_log_file_identifier (current_exe : CLOpt.exe) string_opt =
       (match string_opt with
        | Some name -> name ^ "_"
        | None -> ""
-      ) ^ string_of_int (Unix.getpid ()) ^ "_" in
+      ) ^ Pid.to_string (Unix.getpid ()) ^ "_" in
     let exe_log_dir =
       let log_dir = Config.results_dir // Config.log_dir_name in
       log_dir // (log_dir_of_current_exe current_exe) in
     let fmt_chan_file name suffix = lazy (
       try
-        create_path exe_log_dir ;
+        Unix.mkdir_p exe_log_dir ;
         let file =
           (* the command-line option takes precedence if specified *)
           if name <> "" then name
diff --git a/infer/src/base/Process.ml b/infer/src/base/Process.ml
index f551cfcbd..0b2462018 100644
--- a/infer/src/base/Process.ml
+++ b/infer/src/base/Process.ml
@@ -8,9 +8,6 @@
  *)
 
 open! Utils
-
-module Pid = Core.Std.Pid
-
 module L = Logging
 module F = Format
 
@@ -43,7 +40,6 @@ let create_process_and_wait ~prog ~args =
     represents, prints a message explaining the command and its status, if in debug or stats mode.
     It also prints a dot to show progress of jobs being finished.  *)
 let print_status f pid status =
-  let open Core.Std in
   L.err "%a%s@."
     (fun fmt pid -> F.pp_print_string fmt (f pid)) pid
     (Unix.Exit_or_signal.to_string_hum status) ;
@@ -59,7 +55,6 @@ module PidMap = Map.Make (Pid)
     and all the other children and update the current jobs count.
     Use f to print the job status *)
 let rec wait_for_child f current_jobs_count jobs_map =
-  let open! Core.Std in
   let pid, status = Unix.wait `Any in
   Pervasives.decr current_jobs_count;
   Pervasives.incr waited_for_jobs;
@@ -103,7 +98,7 @@ let run_jobs_in_parallel jobs_stack gen_prog prog_to_string =
   L.out "Waited for %d jobs" !waited_for_jobs
 
 let pipeline ~producer_prog ~producer_args ~consumer_prog ~consumer_args =
-  let open Core.Std in
+  let open! Core.Std in
   let pipe_in, pipe_out = Unix.pipe () in
   match Unix.fork () with
   | `In_the_child ->
diff --git a/infer/src/base/Process.mli b/infer/src/base/Process.mli
index b07bebf81..ebb35c7e5 100644
--- a/infer/src/base/Process.mli
+++ b/infer/src/base/Process.mli
@@ -25,11 +25,11 @@ val print_error_and_exit :
     env)] where [dir_opt] is an optional directory to chdir to before executing [command] with
     [args] in [env]. [prog_to_string] is used for printing information about the job's status. *)
 val run_jobs_in_parallel :
-  'a Stack.t -> ('a -> (string option * string * string list * Core.Std.Unix.env)) -> ('a -> string)
+  'a Stack.t -> ('a -> (string option * string * string list * Unix.env)) -> ('a -> string)
   -> unit
 
 (** Pipeline producer program into consumer program *)
 val pipeline :
   producer_prog:string -> producer_args:string list ->
   consumer_prog:string -> consumer_args:string list ->
-  Core.Std.Unix.Exit_or_signal.t * Core.Std.Unix.Exit_or_signal.t
+  Unix.Exit_or_signal.t * Unix.Exit_or_signal.t
diff --git a/infer/src/base/Serialization.ml b/infer/src/base/Serialization.ml
index c0b3c6f04..9c3cac606 100644
--- a/infer/src/base/Serialization.ml
+++ b/infer/src/base/Serialization.ml
@@ -90,7 +90,7 @@ let create_serializer (key : key) : 'a serializer =
     let outc = open_out_bin fname_tmp in
     Marshal.to_channel outc (key, version, value) [];
     close_out outc;
-    Unix.rename fname_tmp fname_str in
+    Unix.rename ~src:fname_tmp ~dst:fname_str in
   (from_string, from_file, to_file)
 
 
diff --git a/infer/src/base/Utils.ml b/infer/src/base/Utils.ml
index e27f0081f..7e26f62f6 100644
--- a/infer/src/base/Utils.ml
+++ b/infer/src/base/Utils.ml
@@ -12,8 +12,11 @@
 
 module Bool = Core.Std.Bool
 module Filename = Core.Std.Filename
+module In_channel = Core.Std.In_channel
 module Int = Core.Std.Int
+module Pid = Core.Std.Pid
 module String = Core.Std.String
+module Unix = Core.Std.Unix
 
 module F = Format
 
@@ -483,7 +486,7 @@ let remove_directory_tree path =
   |> Stream.iter (fun ent ->
       match Fts.FTSENT.info ent with
       | FTS_D | FTS_DOT -> ()
-      | _ -> Core.Std.Unix.remove (Fts.FTSENT.name ent)
+      | _ -> Unix.remove (Fts.FTSENT.name ent)
     )
 
 
@@ -549,7 +552,7 @@ let create_dir dir =
     if (Unix.stat dir).Unix.st_kind != Unix.S_DIR then
       failwithf "@.ERROR: file %s exists and is not a directory@." dir
   with Unix.Unix_error _ ->
-  try Unix.mkdir dir 0o700 with
+  try Unix.mkdir dir ~perm:0o700 with
     Unix.Unix_error _ ->
       let created_concurrently = (* check if another process created it meanwhile *)
         try (Unix.stat dir).Unix.st_kind = Unix.S_DIR
@@ -557,17 +560,6 @@ let create_dir dir =
       if not created_concurrently then
         failwithf "@.ERROR: cannot create directory %s@." dir
 
-(** [create_path path] will create a directory at [path], creating all the parent directories if
-    non-existing *)
-let rec create_path path =
-  try
-    Unix.mkdir path 0o700
-  with
-  | Unix.Unix_error (Unix.EEXIST, _, _) -> ()
-  | Unix.Unix_error (Unix.ENOENT, _, _) ->
-      create_path (Filename.dirname path);
-      create_dir path
-
 let realpath_cache = Hashtbl.create 1023
 
 let realpath path =
diff --git a/infer/src/base/Utils.mli b/infer/src/base/Utils.mli
index 6f3140199..dd8d6abb8 100644
--- a/infer/src/base/Utils.mli
+++ b/infer/src/base/Utils.mli
@@ -12,8 +12,11 @@
 
 module Bool = Core.Std.Bool
 module Filename = Core.Std.Filename
+module In_channel = Core.Std.In_channel
 module Int = Core.Std.Int
+module Pid = Core.Std.Pid
 module String = Core.Std.String
+module Unix = Core.Std.Unix
 
 (** {2 Generic Utility Functions} *)
 
@@ -227,7 +230,7 @@ val write_json_to_file : string -> Yojson.Basic.json -> unit
 
 val consume_in : in_channel -> unit
 
-val with_process_in: string -> (in_channel -> 'a) -> ('a * Unix.process_status)
+val with_process_in: string -> (in_channel -> 'a) -> ('a * Unix.Exit_or_signal.t)
 
 val failwithf : ('a, Format.formatter, unit, 'b) format4 -> 'a
 
@@ -236,10 +239,6 @@ val invalid_argf : ('a, Format.formatter, unit, 'b) format4 -> 'a
 (** create a directory if it does not exist already *)
 val create_dir : string -> unit
 
-(** [create_path path] will create a directory at [path], creating all the parent directories if
-    non-existing *)
-val create_path : string -> unit
-
 (** [realpath path] returns path with all symbolic links resolved. It caches results of previous
     calls to avoid expensive system calls *)
 val realpath : string -> string
diff --git a/infer/src/base/ZipLib.ml b/infer/src/base/ZipLib.ml
index 924e2456b..7ec36eb9c 100644
--- a/infer/src/base/ZipLib.ml
+++ b/infer/src/base/ZipLib.ml
@@ -30,7 +30,7 @@ let load_from_cache serializer zip_path cache_dir zip_library =
   let extract to_path =
     if not (Sys.file_exists to_path) then
       begin
-        create_path (Filename.dirname to_path);
+        Unix.mkdir_p (Filename.dirname to_path);
         let lazy zip_channel = zip_library.zip_channel in
         let entry = Zip.find_entry zip_channel zip_path in
         Zip.copy_entry_to_file zip_channel entry to_path
diff --git a/infer/src/clang/Capture.re b/infer/src/clang/Capture.re
index 2eae2a26b..096a589e7 100644
--- a/infer/src/clang/Capture.re
+++ b/infer/src/clang/Capture.re
@@ -120,8 +120,8 @@ let run_clang clang_command read => {
   };
   /* NOTE: exceptions will propagate through without exiting here */
   switch (with_process_in clang_command read) {
-  | (res, Unix.WEXITED 0) => res
-  | (_, Unix.WEXITED n) =>
+  | (res, Ok ()) => res
+  | (_, Error (`Exit_non_zero n)) =>
     /* exit with the same error code as clang in case of compilation failure */
     exit_with_error n
   | _ => exit_with_error 1
@@ -143,11 +143,7 @@ let run_plugin_and_frontend source_path frontend clang_args => {
       String.concat
         sep::"^"
         (
-          (
-            try [Unix.getenv CLOpt.args_env_var] {
-            | Not_found => []
-            }
-          ) @ [
+          Core.Std.Option.to_list (Core.Std.Sys.getenv CLOpt.args_env_var) @ [
             "--clang-biniou-file",
             biniou_fname
           ]
diff --git a/infer/src/java/jFrontend.ml b/infer/src/java/jFrontend.ml
index 80f5eb869..0facad7c5 100644
--- a/infer/src/java/jFrontend.ml
+++ b/infer/src/java/jFrontend.ml
@@ -112,7 +112,7 @@ let cache_classname cn =
   let rec mkdir l p =
     let () =
       if not (Sys.file_exists p) then
-        Unix.mkdir p 493 in
+        Unix.mkdir p ~perm:493 in
     match l with
     | [] -> ()
     | d:: tl -> mkdir tl (Filename.concat p d) in