Module Stdlib.Sys

System interface.

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

val argv : string array

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.

val executable_name : string

The name of the file containing the executable currently running.

external file_exists : string -> bool = "caml_sys_file_exists"

Test if a file with the given name exists.

external is_directory : string -> bool = "caml_sys_is_directory"

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.

external remove : string -> unit = "caml_sys_remove"

Remove the given file name from the file system.

external rename : string -> string -> unit = "caml_sys_rename"

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.

external getenv : string -> string = "caml_sys_getenv"

Return the value associated to a variable in the process environment. Raise Not_found if the variable is unbound.

val getenv_opt : string -> string option

Return the value associated to a variable in the process environment or None if the variable is unbound.

external command : string -> int = "caml_sys_system_command"

Execute the given shell command and return its exit code.

external time : unit -> float = "caml_sys_time" "caml_sys_time_unboxed"

Return the processor time, in seconds, used by the program since the beginning of execution.

external chdir : string -> unit = "caml_sys_chdir"

Change the current working directory of the process.

external getcwd : unit -> string = "caml_sys_getcwd"

Return the current working directory of the process.

external readdir : string -> string array = "caml_sys_read_directory"

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.

val interactive : bool Stdlib.ref

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.

val os_type : string

Operating system currently executing the OCaml program. One of

type backend_type =
| Native
| Bytecode
| Other of string

Currently, the official distribution only supports Native and Bytecode, but it can be other backends with alternative compilers, for example, javascript.

val backend_type : backend_type

Backend type currently executing the OCaml program.

val unix : bool

True if Sys.os_type = "Unix".

val win32 : bool

True if Sys.os_type = "Win32".

val cygwin : bool

True if Sys.os_type = "Cygwin".

val word_size : int

Size of one word on the machine currently executing the OCaml program, in bits: 32 or 64.

val int_size : int

Size of an int. It is 31 bits (resp. 63 bits) when using the OCaml compiler on a 32 bits (resp. 64 bits) platform. It may differ for other compilers, e.g. it is 32 bits when compiling to JavaScript.

val big_endian : bool

Whether the machine currently executing the Caml program is big-endian.

val max_string_length : int

Maximum length of strings and byte sequences.

val 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.

external runtime_variant : unit -> string = "caml_runtime_variant"

Return the name of the runtime variant the program is running on. This is normally the argument given to -runtime-variant at compile time, but for byte-code it can be changed after compilation.

external runtime_parameters : unit -> string = "caml_runtime_parameters"

Return the value of the runtime parameters, in the same format as the contents of the OCAMLRUNPARAM environment variable.

Signal handling
type signal_behavior =
| Signal_default
| Signal_ignore
| Signal_handle of int -> unit

What to do when receiving a signal:

external signal : int -> signal_behavior -> signal_behavior = "caml_install_signal_handler"

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.

val set_signal : int -> signal_behavior -> unit

Same as Sys.signal but return value is ignored.

Signal numbers for the standard POSIX signals.
val sigabrt : int

Abnormal termination

val sigalrm : int

Timeout

val sigfpe : int

Arithmetic exception

val sighup : int

Hangup on controlling terminal

val sigill : int

Invalid hardware instruction

val sigint : int

Interactive interrupt (ctrl-C)

val sigkill : int

Termination (cannot be ignored)

val sigpipe : int

Broken pipe

val sigquit : int

Interactive termination

val sigsegv : int

Invalid memory reference

val sigterm : int

Termination

val sigusr1 : int

Application-defined signal 1

val sigusr2 : int

Application-defined signal 2

val sigchld : int

Child process terminated

val sigcont : int

Continue

val sigstop : int

Stop

val sigtstp : int

Interactive stop

val sigttin : int

Terminal read from background process

val sigttou : int

Terminal write from background process

val sigvtalrm : int

Timeout in virtual time

val sigprof : int

Profiling interrupt

val sigbus : int

Bus error

val sigpoll : int

Pollable event

val sigsys : int

Bad argument to routine

val sigtrap : int

Trace/breakpoint trap

val sigurg : int

Urgent condition on socket

val sigxcpu : int

Timeout in cpu time

val sigxfsz : int

File size limit exceeded

exception Break

Exception raised on interactive interrupt if Sys.catch_break is on.

val 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.

val 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.

val enable_runtime_warnings : bool -> unit

Control whether the OCaml runtime system can emit warnings on stderr. Currently, the only supported warning is triggered when a channel created by open_* functions is finalized without being closed. Runtime warnings are enabled by default.

val runtime_warnings_enabled : unit -> bool

Return whether runtime warnings are currently enabled.

Optimization
external opaque_identity : 'a -> 'a = "%opaque"

For the purposes of optimization, opaque_identity behaves like an unknown (and thus possibly side-effecting) function.

At runtime, opaque_identity disappears altogether.

A typical use of this function is to prevent pure computations from being optimized away in benchmarking loops. For example: 


      for _round = 1 to 100_000 do
        ignore (Sys.opaque_identity (my_pure_computation ()))
      done