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       ocaml - The OCaml interactive toplevel


       ocaml [ options ] [ object-files ] [ script-file ]


       The ocaml(1) command is the toplevel system for OCaml, that permits interactive use of the
       OCaml system through a read-eval-print loop. In this mode,  the  system  repeatedly  reads
       OCaml  phrases  from  the input, then typechecks, compiles and evaluates them, then prints
       the inferred type and result value, if any. The system prints a  #  (hash)  prompt  before
       reading each phrase.

       A toplevel phrase can span several lines. It is terminated by ;; (a double-semicolon). The
       syntax of toplevel phrases is as follows.

       The toplevel system is started by the command ocaml(1).   Phrases  are  read  on  standard
       input,  results  are  printed on standard output, errors on standard error. End-of-file on
       standard input terminates ocaml(1).

       If one or more object-files (ending in .cmo or .cma) are given, they are  loaded  silently
       before starting the toplevel.

       If  a  script-file  is  given,  phrases are read silently from the file, errors printed on
       standard error.  ocaml(1) exits after the execution of the last phrase.


       The following command-line options are recognized by ocaml(1).

              Show absolute filenames in error messages.

       -I directory
              Add the given directory to the list of directories searched for source and compiled
              files.  By  default,  the  current  directory  is searched first, then the standard
              library directory. Directories  added  with  -I  are  searched  after  the  current
              directory,  in  the  order in which they were given on the command line, but before
              the standard library directory.

              If the given directory starts with +, it is taken relative to the standard  library
              directory.  For  instance, -I +compiler-libs adds the subdirectory compiler-libs of
              the standard library to the search path.

              Directories can also be added to the search path once the toplevel is running  with
              the #directory directive.

       -init file
              Load  the  given  file  instead  of  the  default  initialization  file.   See  the
              "Initialization file" section below.

              Labels are not ignored in types, labels may be used in applications,  and  labelled
              parameters can be given in any order.  This is the default.

              Deactivates  the  applicative behaviour of functors. With this option, each functor
              application generates new types in its result and applying the same  functor  twice
              to the same argument yields two incompatible structures.

              Do not compile assertion checks.  Note that the special form assert false is always
              compiled because it is typed specially.

              Do not load any initialization file.  See the "Initialization file" section below.

              Ignore non-optional labels in types. Labels cannot be  used  in  applications,  and
              parameter order becomes strict.

              Do not display any prompt when waiting for input.

              Do  not  display the secondary prompt when waiting for continuation lines in multi-
              line inputs.  This should be used e.g. when running ocaml(1) in an emacs(1) window.

              Do not include the standard library directory in the list of  directories  searched
              for source and compiled files.

       -open module
              Opens  the  given module before starting the toplevel. If several -open options are
              given, they are processed in order, just as if the statements open!  module1;;  ...
              open! moduleN;; were input.

       -ppx command
              After parsing, pipe the abstract syntax tree through the preprocessor command.  The
              module Ast_mapper(3) implements the external interface of a preprocessor.

              Check information path during type-checking,  to  make  sure  that  all  types  are
              derived  in  a  principal  way.   When  using labelled arguments and/or polymorphic
              methods, this flag is required to ensure future versions of the  compiler  will  be
              able  to  infer  types correctly, even if internal algorithms change.  All programs
              accepted in -principal mode are also accepted in the default mode  with  equivalent
              types,  but  different binary signatures, and this may slow down type checking; yet
              it is a good idea to use it once before publishing source code.

              Allow arbitrary recursive types during type-checking.  By default,  only  recursive
              types where the recursion goes through an object type are supported.

              Enforce the separation between types string and bytes, thereby making strings read-
              only. This is the default.

              When a type is visible under  several  module-paths,  use  the  shortest  one  when
              printing the type's name in inferred interfaces and error and warning messages.

       -stdin Read  the  standard  input  as  a  script  file rather than starting an interactive

              Force the left-hand part of each sequence to have type unit.

              When a type is unboxable (i.e. a record  with  a  single  argument  or  a  concrete
              datatype  with  a  single  constructor  of  one argument) it will be unboxed unless
              annotated with [@@ocaml.boxed].

              When a type is unboxable  it will be boxed unless annotated with [@@ocaml.unboxed].
              This is the default.

              Turn   bound   checking  off  on  array  and  string  accesses  (the  v.(i)ands.[i]
              constructs). Programs compiled with -unsafe  are  therefore  slightly  faster,  but
              unsafe:  anything  can happen if the program accesses an array or string outside of
              its bounds.

              Identify the types string and bytes, thereby  making  strings  writable.   This  is
              intended  for  compatibility  with  old source code and should not be used with new

              Print version string and exit.

       -vnum  Print short version number and exit.

              Do not print the version banner at startup.

       -w warning-list
              Enable or disable warnings according to the argument warning-list.   See  ocamlc(1)
              for the syntax of the warning-list argument.

       -warn-error warning-list
              Mark  as  fatal  the  warnings described by the argument warning-list.  Note that a
              warning is not triggered (and does not trigger an error) if it is disabled  by  the
              -w option.  See ocamlc(1) for the syntax of the warning-list argument.

       -color mode
              Enable  or  disable  colors  in compiler messages (especially warnings and errors).
              The following modes are supported:

              auto use heuristics to enable colors only if the output  supports  them  (an  ANSI-
              compatible tty terminal);

              always enable colors unconditionally;

              never disable color output.

              The  default  setting  is  auto,  and  the current heuristic checks that the "TERM"
              environment variable exists and is not empty or  "dumb",  and  that  isatty(stderr)

              The environment variable "OCAML_COLOR" is considered if -color is not provided. Its
              values are auto/always/never as above.

       -error-style mode
              Control the way error messages and warnings are printed.  The following  modes  are

              short only print the error and its location;

              contextual  like "short", but also display the source code snippet corresponding to
              the location of the error.

              The default setting is contextual.

              The environment variable "OCAML_ERROR_STYLE" is considered if -error-style  is  not
              provided. Its values are short/contextual as above.

              Show the description of all available warning numbers.

       - file Use file as a script file name, even when it starts with a hyphen (-).

       -help or --help
              Display a short usage summary and exit.


       When  ocaml(1)  is invoked, it will read phrases from an initialization file before giving
       control to the user. The default file is .ocamlinit in the current directory if it exists,
       otherwise  XDG_CONFIG_HOME/ocaml/ according to the XDG base directory specification
       lookup if it exists (on Windows this is skipped), otherwise .ocamlinit in the user's  home
       directory  ( HOME variable).  You can specify a different initialization file by using the
       -init file option, and disable initialization files by using the -noinit option.

       Note that you can also use the #use directive to read phrases from a file.


              When printing string values, non-ascii bytes (>0x7E) are printed as decimal  escape
              sequence if OCAMLTOP_UTF_8 is set to false. Otherwise they are printed unescaped.

       TERM   When  printing  error  messages, the toplevel system attempts to underline visually
              the location of the error. It consults the TERM variable to determines the type  of
              output terminal and look up its capabilities in the terminal database.

              .ocamlinit lookup procedure (see above).


       ocamlc(1), ocamlopt(1), ocamlrun(1).
       The OCaml user's manual, chapter "The toplevel system".