1OCAML(1) General Commands Manual OCAML(1)
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6 ocaml - The OCaml interactive toplevel
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10 ocaml [ options ] [ object-files ] [ script-file ]
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13 The ocaml(1) command is the toplevel system for OCaml, that permits in‐
14 teractive use of the OCaml system through a read-eval-print loop. In
15 this mode, the system repeatedly reads OCaml phrases from the input,
16 then typechecks, compiles and evaluates them, then prints the inferred
17 type and result value, if any. The system prints a # (hash) prompt be‐
18 fore reading each phrase.
19 A toplevel phrase can span several lines. It is terminated by ;; (a
21 double-semicolon). The syntax of toplevel phrases is as follows.
22 The toplevel system is started by the command ocaml(1). Phrases are
24 read on standard input, results are printed on standard output, errors
25 on standard error. End-of-file on standard input terminates ocaml(1).
26 If one or more object-files (ending in .cmo or .cma) are given, they
28 are loaded silently before starting the toplevel.
29 If a script-file is given, phrases are read silently from the file, er‐
31 rors printed on standard error. ocaml(1) exits after the execution of
32 the last phrase.
33
36 The following command-line options are recognized by ocaml(1).
37 -absname
39 Show absolute filenames in error messages.
40 -I directory
42 Add the given directory to the list of directories searched for
43 source and compiled files. By default, the current directory is
44 searched first, then the standard library directory. Directories
45 added with -I are searched after the current directory, in the
46 order in which they were given on the command line, but before
47 the standard library directory.
48 If the given directory starts with +, it is taken relative to
50 the standard library directory. For instance, -I +compiler-libs
51 adds the subdirectory compiler-libs of the standard library to
52 the search path.
53 Directories can also be added to the search path once the
55 toplevel is running with the #directory directive.
56 -init file
58 Load the given file instead of the default initialization file.
59 See the "Initialization file" section below.
60 -labels
62 Labels are not ignored in types, labels may be used in applica‐
63 tions, and labelled parameters can be given in any order. This
64 is the default.
65 -no-app-funct
67 Deactivates the applicative behaviour of functors. With this op‐
68 tion, each functor application generates new types in its result
69 and applying the same functor twice to the same argument yields
70 two incompatible structures.
71 -noassert
73 Do not compile assertion checks. Note that the special form as‐
74 sert false is always compiled because it is typed specially.
75 -noinit
77 Do not load any initialization file. See the "Initialization
78 file" section below.
79 -nolabels
81 Ignore non-optional labels in types. Labels cannot be used in
82 applications, and parameter order becomes strict.
83 -noprompt
85 Do not display any prompt when waiting for input.
86 -nopromptcont
88 Do not display the secondary prompt when waiting for continua‐
89 tion lines in multi-line inputs. This should be used e.g. when
90 running ocaml(1) in an emacs(1) window.
91 -nostdlib
93 Do not include the standard library directory in the list of di‐
94 rectories searched for source and compiled files.
95 -open module
97 Opens the given module before starting the toplevel. If several
98 -open options are given, they are processed in order, just as if
99 the statements open! module1;; ... open! moduleN;; were input.
100 -ppx command
102 After parsing, pipe the abstract syntax tree through the pre‐
103 processor command. The module Ast_mapper(3) implements the ex‐
104 ternal interface of a preprocessor.
105 -principal
107 Check information path during type-checking, to make sure that
108 all types are derived in a principal way. When using labelled
109 arguments and/or polymorphic methods, this flag is required to
110 ensure future versions of the compiler will be able to infer
111 types correctly, even if internal algorithms change. All pro‐
112 grams accepted in -principal mode are also accepted in the de‐
113 fault mode with equivalent types, but different binary signa‐
114 tures, and this may slow down type checking; yet it is a good
115 idea to use it once before publishing source code.
116 -rectypes
118 Allow arbitrary recursive types during type-checking. By de‐
119 fault, only recursive types where the recursion goes through an
120 object type are supported.
121 -safe-string
123 Enforce the separation between types string and bytes, thereby
124 making strings read-only. This is the default.
125 -short-paths
127 When a type is visible under several module-paths, use the
128 shortest one when printing the type's name in inferred inter‐
129 faces and error and warning messages.
130 -stdin Read the standard input as a script file rather than starting an
132 interactive session.
133 -strict-sequence
135 Force the left-hand part of each sequence to have type unit.
136 -unboxed-types
138 When a type is unboxable (i.e. a record with a single argument
139 or a concrete datatype with a single constructor of one argu‐
140 ment) it will be unboxed unless annotated with [@@ocaml.boxed].
141 -no-unboxed-types
143 When a type is unboxable it will be boxed unless annotated with
144 [@@ocaml.unboxed]. This is the default.
145 -unsafe
147 Turn bound checking off on array and string accesses (the
148 v.(i)ands.[i] constructs). Programs compiled with -unsafe are
149 therefore slightly faster, but unsafe: anything can happen if
150 the program accesses an array or string outside of its bounds.
151 -unsafe-string
153 Identify the types string and bytes, thereby making strings
154 writable. This is intended for compatibility with old source
155 code and should not be used with new software.
156 -version
158 Print version string and exit.
159 -vnum Print short version number and exit.
161 -no-version
163 Do not print the version banner at startup.
164 -w warning-list
166 Enable or disable warnings according to the argument warning-
167 list. See ocamlc(1) for the syntax of the warning-list argu‐
168 ment.
169 -warn-error warning-list
171 Mark as fatal the warnings described by the argument warn‐
172 ing-list. Note that a warning is not triggered (and does not
173 trigger an error) if it is disabled by the -w option. See
174 ocamlc(1) for the syntax of the warning-list argument.
175 -color mode
177 Enable or disable colors in compiler messages (especially warn‐
178 ings and errors). The following modes are supported:
179 auto use heuristics to enable colors only if the output supports
181 them (an ANSI-compatible tty terminal);
182 always enable colors unconditionally;
184 never disable color output.
186 The environment variable "OCAML_COLOR" is considered if -color
188 is not provided. Its values are auto/always/never as above.
189 If -color is not provided, "OCAML_COLOR" is not set and the en‐
191 vironment variable "NO_COLOR" is set, then color output is dis‐
192 abled. Otherwise, the default setting is auto, and the current
193 heuristic checks that the "TERM" environment variable exists and
194 is not empty or "dumb", and that isatty(stderr) holds.
195 -error-style mode
198 Control the way error messages and warnings are printed. The
199 following modes are supported:
200 short only print the error and its location;
202 contextual like "short", but also display the source code snip‐
204 pet corresponding to the location of the error.
205 The default setting is contextual.
207 The environment variable "OCAML_ERROR_STYLE" is considered if
209 -error-style is not provided. Its values are short/contextual as
210 above.
211 -warn-help
214 Show the description of all available warning numbers.
215 - file Use file as a script file name, even when it starts with a hy‐
217 phen (-).
218 -help or --help
220 Display a short usage summary and exit.
221
224 When ocaml(1) is invoked, it will read phrases from an initialization
225 file before giving control to the user. The default file is .ocamlinit
226 in the current directory if it exists, otherwise XDG_CON‐
227 FIG_HOME/ocaml/init.ml according to the XDG base directory specifica‐
228 tion lookup if it exists (on Windows this is skipped), otherwise .ocam‐
229 linit in the user's home directory ( HOME variable). You can specify a
230 different initialization file by using the -init file option, and dis‐
231 able initialization files by using the -noinit option.
232 Note that you can also use the #use directive to read phrases from a
234 file.
235
238 OCAMLTOP_UTF_8
239 When printing string values, non-ascii bytes (>0x7E) are printed
240 as decimal escape sequence if OCAMLTOP_UTF_8 is set to false.
241 Otherwise they are printed unescaped.
242 TERM When printing error messages, the toplevel system attempts to
244 underline visually the location of the error. It consults the
245 TERM variable to determines the type of output terminal and look
246 up its capabilities in the terminal database.
247 XDG_CONFIG_HOME HOME
249 .ocamlinit lookup procedure (see above).
250
252 ocamlc(1), ocamlopt(1), ocamlrun(1).
253 The OCaml user's manual, chapter "The toplevel system".
254 OCAML(1)