Ubuntu Manpage: ocaml - The OCaml interactive toplevel

name
synopsis
description
options
initialization file
environment variables
see also

NAME

       ocaml - The OCaml interactive toplevel

SYNOPSIS

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

DESCRIPTION

       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  standard
       input,  then  typechecks, compiles and evaluates them, then prints the inferred type and result value, if
       any.  End-of-file on standard input terminates ocaml(1).

       Input to the toplevel can span several lines. It begins after the # (sharp) prompt printed by the  system
       and  is  terminated  by ;; (a double-semicolon) followed by optional white space and an end of line.  The
       toplevel input consists in one or several toplevel phrases.

       If one or more object-files (ending in .cmo or .cma) are given on  the  command  line,  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.

OPTIONS

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

-absname
Show absolute filenames in error messages.

-no-absname
Do not try to 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
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.

-no-app-funct
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.

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

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

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

-noprompt
Do not display any prompt when waiting for input.

-nopromptcont
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.

-nostdlib
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.

-principal
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.

-no-principal
Do not check principality of type inference. This is the default.

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

-no-rectypes
Do no allow arbitrary recursive types during type-checking. This is the default.

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

-safer-matching
Do not use type information to optimize pattern-matching. This allows to detect match failures
even if a pattern-matching was wrongly assumed to be exhaustive. This only impacts GADT and
polymorphic variant compilation.

-short-paths
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.

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

-no-strict-sequence
Left-hand part of a sequence need not have type unit. This is the default.

-unboxed-types
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].

-no-unboxed-types
When a type is unboxable it will be boxed unless annotated with [@@ocaml.unboxed]. This is the
default.

-unsafe
Turn bound checking off on array and string accesses (the v.(i) and s.[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.

-unsafe-string
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.

-version
Print version string and exit.

-vnum Print short version number and exit.

-no-version
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 environment variable "OCAML_COLOR" is considered if -color is not provided. Its values are
auto/always/never as above.

If -color is not provided, "OCAML_COLOR" is not set and the environment variable "NO_COLOR" is
set, then color output is disabled. Otherwise, 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) holds.

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

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.

-warn-help
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.

INITIALIZATION FILE

       When ocaml(1) is invoked, it will read phrases from an initialization file before giving control  to  the
       user. The file read is the first found of:

       1.     .ocamlinit in the current directory;

       2.     XDG_CONFIG_HOME/ocaml/init.ml, if XDG_CONFIG_HOME is an absolute path;

       3.     otherwise,  on  Unix,  HOME/ocaml/init.ml  or,  on Windows, ocaml\init.ml under LocalAppData (e.g.
              C:\Users\Bactrian\AppData\Local\ocaml\init.ml);

       4.     ocaml/init.ml under any of the absolute paths in XDG_CONFIG_DIRS.  Paths  in  XDG_CONFIG_DIRS  are
              colon-delimited on Unix, and semicolon-delimited on Windows;

       5.     if  XDG_CONFIG_DIRS  contained no absolute paths, /usr/xdg/ocaml/init.ml on Unix or, ocaml\init.ml
              under  any  of   LocalAppData   (e.g.   C:\Users\Bactrian\AppData\Local),   RoamingAppData   (e.g.
              C:\Users\Bactrian\AppData\Roaming), or ProgramData (e.g. C:\ProgramData) on Windows;

       6.     HOME/.ocamlinit, if HOME is non-empty;

              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.

ENVIRONMENT VARIABLES

       OCAMLTOP_UTF_8
              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.

       XDG_CONFIG_HOME HOME XDG_CONFIG_DIRS
              See INITIALIZATION FILE above.