sys: system interface

This module provides a simple interface to the operating system.

exception Sys_error of string

Raised by some functions in the sys and io modules, when the underlying system calls fail. The argument to Sys_error is a string describing the error. The texts of the error messages are implementation-dependent, and should not be relied upon to catch specific system errors.

value command_line : string vect

The command line arguments given to the process. The first element is the command name used to invoke the program.

value interactive: bool

True if we're running under the toplevel system. False if we're running as a standalone program.

type file_perm == int
value s_irusr : file_perm
value s_iwusr : file_perm
value s_ixusr : file_perm
value s_irgrp : file_perm
value s_iwgrp : file_perm
value s_ixgrp : file_perm
value s_iroth : file_perm
value s_iwoth : file_perm
value s_ixoth : file_perm
value s_isuid : file_perm
value s_isgid : file_perm
value s_irall : file_perm
value s_iwall : file_perm
value s_ixall : file_perm

Access permissions for files. r is reading permission, w is writing permission, x is execution permission. usr means permissions for the user owning the file, grp for the group owning the file, oth for others. isuid and isgid are for set-user-id and set-group-id files, respectively. The remaining are combinations of the permissions above.

type open_flag =
    O_RDONLY                       (* open read-only *)
  | O_WRONLY                       (* open write-only *)
  | O_RDWR                         (* open for reading and writing *)
  | O_APPEND                       (* open for appending *)
  | O_CREAT                        (* create the file if nonexistent *)
  | O_TRUNC                        (* truncate the file to 0 if it exists *)
  | O_EXCL                         (* fails if the file exists *)
  | O_BINARY                       (* open in binary mode *)
  | O_TEXT                         (* open in text mode *)

The commands for open.

value exit : int -> 'a

Terminate the program and return the given status code to the operating system. In contrast with the function exit from module io, this exit function does not flush the standard output and standard error channels.

value open : string -> open_flag list -> file_perm -> int

Open a file. The second argument is the opening mode. The third argument is the permissions to use if the file must be created. The result is a file descriptor opened on the file.

value close : int -> unit

Close a file descriptor.

value remove : string -> unit

Remove the given file name from the file system.

value rename : string -> string -> unit

Rename a file. The first argument is the old name and the second is the new name.

value getenv : string -> string

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

value chdir : string -> unit

Change the current working directory of the process. Note that there is no easy way of getting the current working directory from the operating system.

value system_command : string -> int

Execute the given shell command and return its exit code.

value time : unit -> float

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

exception Break

Exception Break is raised on user interrupt if catch_break is on.

value catch_break : bool -> unit

catch_break governs whether user interrupt 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.