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
14 interactive 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
18 before 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,
31 errors printed on standard error. ocaml(1) exits after the execution
32 of 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
68 option, each functor application generates new types in its
69 result and applying the same functor twice to the same argument
70 yields two incompatible structures.
71 -noassert
73 Do not compile assertion checks. Note that the special form
74 assert 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
94 directories 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
104 external 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
113 default 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
119 default, only recursive types where the recursion goes through
120 an 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 default setting is auto, and the current heuristic checks
188 that the "TERM" environment variable exists and is not empty or
189 "dumb", and that isatty(stderr) holds.
190 The environment variable "OCAML_COLOR" is considered if -color
192 is not provided. Its values are auto/always/never as above.
193 -error-style mode
196 Control the way error messages and warnings are printed. The
197 following modes are supported:
198 short only print the error and its location;
200 contextual like "short", but also display the source code snip‐
202 pet corresponding to the location of the error.
203 The default setting is contextual.
205 The environment variable "OCAML_ERROR_STYLE" is considered if
207 -error-style is not provided. Its values are short/contextual as
208 above.
209 -warn-help
212 Show the description of all available warning numbers.
213 - file Use file as a script file name, even when it starts with a
215 hyphen (-).
216 -help or --help
218 Display a short usage summary and exit.
219
222 When ocaml(1) is invoked, it will read phrases from an initialization
223 file before giving control to the user. The default file is .ocamlinit
224 in the current directory if it exists, otherwise XDG_CON‐
225 FIG_HOME/ocaml/init.ml according to the XDG base directory specifica‐
226 tion lookup if it exists (on Windows this is skipped), otherwise .ocam‐
227 linit in the user's home directory ( HOME variable). You can specify a
228 different initialization file by using the -init file option, and dis‐
229 able initialization files by using the -noinit option.
230 Note that you can also use the #use directive to read phrases from a
232 file.
233
236 OCAMLTOP_UTF_8
237 When printing string values, non-ascii bytes (>0x7E) are printed
238 as decimal escape sequence if OCAMLTOP_UTF_8 is set to false.
239 Otherwise they are printed unescaped.
240 TERM When printing error messages, the toplevel system attempts to
242 underline visually the location of the error. It consults the
243 TERM variable to determines the type of output terminal and look
244 up its capabilities in the terminal database.
245 XDG_CONFIG_HOME HOME
247 .ocamlinit lookup procedure (see above).
248
250 ocamlc(1), ocamlopt(1), ocamlrun(1).
251 The OCaml user's manual, chapter "The toplevel system".
252 OCAML(1)