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Standard Library

Below is the API for the OCaml standard library. It's directly copied over from the OCaml Manual, formatted to the Reason syntax and styled accordingly. The API docs are work-in-progress; we'll be polishing these gradually!

If you're targeting JavaScript, the API docs for BuckleScript includes all of below, plus JS-specific APIs.

Module Sys

module Sys: sig .. end
System interface.

Every function in this module raises Sys_error with an informative message when the underlying system call signal an error.


let argv: array(string);
The command line arguments given to the process. The first element is the command name used to invoke the program. The following elements are the command-line arguments given to the program.
let executable_name: string;
The name of the file containing the executable currently running.
let file_exists: string => bool;
Test if a file with the given name exists.
let is_directory: string => bool;
Returns true if the given name refers to a directory, false if it refers to another kind of file. Raise Sys_error if no file exists with the given name.
Since 3.10.0
let remove: string => unit;
Remove the given file name from the file system.
let rename: (string, string) => unit;
Rename a file. The first argument is the old name and the second is the new name. If there is already another file under the new name, rename may replace it, or raise an exception, depending on your operating system.
let getenv: string => string;
Return the value associated to a variable in the process environment. Raise Not_found if the variable is unbound.
let command: string => int;
Execute the given shell command and return its exit code.
let time: unit => float;
Return the processor time, in seconds, used by the program since the beginning of execution.
let chdir: string => unit;
Change the current working directory of the process.
let getcwd: unit => string;
Return the current working directory of the process.
let readdir: string => array(string);
Return the names of all files present in the given directory. Names denoting the current directory and the parent directory ("." and ".." in Unix) are not returned. Each string in the result is a file name rather than a complete path. There is no guarantee that the name strings in the resulting array will appear in any specific order; they are not, in particular, guaranteed to appear in alphabetical order.
let interactive: Pervasives.ref(bool);
This reference is initially set to false in standalone programs and to true if the code is being executed under the interactive toplevel system ocaml.
let os_type: string;
Operating system currently executing the OCaml program. One of
  • "Unix" (for all Unix versions, including Linux and Mac OS X),
  • "Win32" (for MS-Windows, OCaml compiled with MSVC++ or Mingw),
  • "Cygwin" (for MS-Windows, OCaml compiled with Cygwin).

let unix: bool;
True if Sys.os_type = "Unix".
Since 4.01.0
let win32: bool;
True if Sys.os_type = "Win32".
Since 4.01.0
let cygwin: bool;
True if Sys.os_type = "Cygwin".
Since 4.01.0
let word_size: int;
Size of one word on the machine currently executing the OCaml program, in bits: 32 or 64.
let big_endian: bool;
Whether the machine currently executing the Caml program is big-endian.
Since 4.00.0
let max_string_length: int;
Maximum length of strings and byte sequences.
let max_array_length: int;
Maximum length of a normal array. The maximum length of a float array is max_array_length/2 on 32-bit machines and max_array_length on 64-bit machines.

Signal handling

type signal_behavior = 
| Signal_default
| Signal_ignore
| Signal_handle of (int -> unit) (*
*)
What to do when receiving a signal:
  • Signal_default: take the default behavior (usually: abort the program)
  • Signal_ignore: ignore the signal
  • Signal_handle f: call function f, giving it the signal number as argument.

let signal: (int, signal_behavior) => signal_behavior;
Set the behavior of the system on receipt of a given signal. The first argument is the signal number. Return the behavior previously associated with the signal. If the signal number is invalid (or not available on your system), an Invalid_argument exception is raised.
let set_signal: (int, signal_behavior) => unit;
Same as Sys.signal but return value is ignored.

Signal numbers for the standard POSIX signals.

let sigabrt: int;
Abnormal termination
let sigalrm: int;
Timeout
let sigfpe: int;
Arithmetic exception
let sighup: int;
Hangup on controlling terminal
let sigill: int;
Invalid hardware instruction
let sigint: int;
Interactive interrupt (ctrl-C)
let sigkill: int;
Termination (cannot be ignored)
let sigpipe: int;
Broken pipe
let sigquit: int;
Interactive termination
let sigsegv: int;
Invalid memory reference
let sigterm: int;
Termination
let sigusr1: int;
Application-defined signal 1
let sigusr2: int;
Application-defined signal 2
let sigchld: int;
Child process terminated
let sigcont: int;
Continue
let sigstop: int;
Stop
let sigtstp: int;
Interactive stop
let sigttin: int;
Terminal read from background process
let sigttou: int;
Terminal write from background process
let sigvtalrm: int;
Timeout in virtual time
let sigprof: int;
Profiling interrupt
exception Break;
Exception raised on interactive interrupt if Sys.catch_break is on.
let catch_break: bool => unit;
catch_break governs whether interactive interrupt (ctrl-C) terminates the program or raises the Break exception. Call catch_break true to enable raising Break, and catch_break false to let the system terminate the program on user interrupt.
let ocaml_version: string;
ocaml_version is the version of OCaml. It is a string of the form "major.minor[.patchlevel][+additional-info]", where major, minor, and patchlevel are integers, and additional-info is an arbitrary string. The [.patchlevel] and [+additional-info] parts may be absent.