Exec command from OCaml

OCaml

Just run the command:

Sys.command "ls"

To capture the output of the command:

#load "unix.cma"
 
let syscall cmd =
  let ic, oc = Unix.open_process cmd in
  let buf = Buffer.create 16 in
  (try
     while true do
       Buffer.add_channel buf ic 1
     done
   with End_of_file -> ());
  let _ = Unix.close_process (ic, oc) in
  (Buffer.contents buf)
 
let listing = syscall "ls" ;;

a more complete version which also returns the contents from stderr, and checks the exit-status, and where the environment can be specified:

let check_exit_status = function
  | Unix.WEXITED 0 -> ()
  | Unix.WEXITED r -> Printf.eprintf "warning: the process terminated with exit code (%d)\n%!" r
  | Unix.WSIGNALED n -> Printf.eprintf "warning: the process was killed by a signal (number: %d)\n%!" n
  | Unix.WSTOPPED n -> Printf.eprintf "warning: the process was stopped by a signal (number: %d)\n%!" n
;;
 
let syscall ?(env=[| |]) cmd =
  let ic, oc, ec = Unix.open_process_full cmd env in
  let buf1 = Buffer.create 96
  and buf2 = Buffer.create 48 in
  (try
     while true do Buffer.add_channel buf1 ic 1 done
   with End_of_file -> ());
  (try
     while true do Buffer.add_channel buf2 ec 1 done
   with End_of_file -> ());
  let exit_status = Unix.close_process_full (ic, oc, ec) in
  check_exit_status exit_status;
  (Buffer.contents buf1,
   Buffer.contents buf2)

val syscall : ?env:string array -> string -> string * string

http://rosettacode.org/wiki/Execute_a_system_command#OCaml