OCAML(1) General Commands Manual OCAML(1)
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 in-
teractive 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 be-
fore 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, er-
rors 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.
-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 applica-
tions, and labelled parameters can be given in any order. This
is the default.
-no-app-funct
Deactivates the applicative behaviour of functors. With this op-
tion, 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 as-
sert 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 continua-
tion 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 di-
rectories 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 pre-
processor command. The module Ast_mapper(3) implements the ex-
ternal 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 pro-
grams accepted in -principal mode are also accepted in the de-
fault mode with equivalent types, but different binary signa-
tures, and this may slow down type checking; yet it is a good
idea to use it once before publishing source code.
-rectypes
Allow arbitrary recursive types during type-checking. By de-
fault, only recursive types where the recursion goes through an
object type are supported.
-safe-string
Enforce the separation between types string and bytes, thereby
making strings read-only. This is the default.
-short-paths
When a type is visible under several module-paths, use the
shortest one when printing the type's name in inferred inter-
faces 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.
-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 argu-
ment) 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)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.
-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 argu-
ment.
-warn-error warning-list
Mark as fatal the warnings described by the argument warn-
ing-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 warn-
ings 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) holds.
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 supported:
short only print the error and its location;
contextual like "short", but also display the source code snip-
pet 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 hy-
phen (-).
-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 default file is .ocamlinit
in the current directory if it exists, otherwise XDG_CON-
FIG_HOME/ocaml/init.ml according to the XDG base directory specifica-
tion lookup if it exists (on Windows this is skipped), otherwise .ocam-
linit in the user's home directory ( HOME variable). You can specify a
different initialization file by using the -init file option, and dis-
able 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
.ocamlinit lookup procedure (see above).
SEE ALSO
ocamlc(1), ocamlopt(1), ocamlrun(1).
The OCaml user's manual, chapter "The toplevel system".
OCAML(1)
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