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Module Sys: system interface

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 arguments given to the program. 
val file_exists: string -> bool
Test if a file with the given name exists. 
val remove: string -> unit
Remove the given file name from the file system. 
val rename : string -> string -> unit
Rename a file. The first argument is the old name and the second is the new name. 
val getenv: string -> string
Return the value associated to a variable in the process environment. Raise Not_found if the variable is unbound. 
val command: string -> int
Execute the given shell command and return its exit code. 
val chdir: string -> unit
Change the current working directory of the process. 
val getcwd: unit -> string
Return the current working directory of the process. 
val interactive: bool ref
This reference is initially set to false in standalone programs and to true if the code is being executed under the interactive toplevel csltop. 
val os_type: string
Operating system currently executing the Caml program. One of "Unix", "Win32", or "MacOS". 
val word_size: int
Size of one word on the machine currently executing the Caml program, in bits: 32 or 64. 
val max_string_length: int
Maximum length of a string. 
val max_array_length: int
Maximum length of an array.

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
Signal_ignore: ignore the signal
Signal_handle f: call function f, giving it the signal number as argument. 
val signal: int -> signal_behavior -> unit
Set the behavior of the system on receipt of a given signal. The first argument is the signal number. 
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 *)
Signal numbers for the standard POSIX signals. 
exception Break
Exception raised on interactive interrupt if 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.
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