OCAML(1)                    General Commands Manual                   OCAML(1)

       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 session.

              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

              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 software.

              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

       -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.

              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 .ocamlinit in the
       user's home directory. 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

              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.

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