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Chapter 28 The unix library: Unix system calls

The unix library makes many Unix system calls and system-related library functions available to OCaml programs. This chapter describes briefly the functions provided. Refer to sections 2 and 3 of the Unix manual for more details on the behavior of these functions.

Not all functions are provided by all Unix variants. If some functions are not available, they will raise Invalid_arg when called.

Programs that use the unix library must be linked as follows:

        ocamlc other options unix.cma other files
        ocamlopt other options unix.cmxa other files

For interactive use of the unix library, do:

        ocamlmktop -o mytop unix.cma
        ./mytop

or (if dynamic linking of C libraries is supported on your platform), start ocaml and type #load "unix.cma";;.

Windows: A fairly complete emulation of the Unix system calls is provided in the Windows version of OCaml. The end of this chapter gives more information on the functions that are not supported under Windows.

Windows: The Cygwin port of OCaml fully implements all functions from the Unix module. The native Win32 ports implement a subset of them. Below is a list of the functions that are not implemented, or only partially implemented, by the Win32 ports. Functions not mentioned are fully implemented and behave as described previously in this chapter.

Functions Comment

fork not implemented, use create_process or threads

wait not implemented, use waitpid

waitpid can only wait for a given PID, not any child process

getppid not implemented (meaningless under Windows)

nice not implemented

truncate, ftruncate not implemented

link implemented (since 3.02)

symlink, readlink implemented (since 4.03.0)

access execute permission X_OK cannot be tested, it just tests for read permission instead

fchmod not implemented

chown, fchown not implemented (make no sense on a DOS file system)

umask not implemented

mkfifo not implemented

kill partially implemented (since 4.00.0): only the sigkill signal is implemented

pause not implemented (no inter-process signals in Windows)

alarm not implemented

times partially implemented, will not report timings for child processes

getitimer, setitimer not implemented

getuid, geteuid, getgid, getegid always return 1

getgroups always returns [|1|] (since 2.00)

setuid, setgid, setgroups not implemented

getpwnam, getpwuid always raise Not_found

getgrnam, getgrgid always raise Not_found

type socket_domain PF_INET is fully supported; PF_INET6 is fully supported (since 4.01.0); PF_UNIX is not supported

establish_server not implemented; use threads

terminal functions (tc*) not implemented

Functions	Comment
fork	not implemented, use create_process or threads
wait	not implemented, use waitpid
waitpid	can only wait for a given PID, not any child process
getppid	not implemented (meaningless under Windows)
nice	not implemented
truncate, ftruncate	not implemented
link	implemented (since 3.02)
symlink, readlink	implemented (since 4.03.0)
access	execute permission X_OK cannot be tested, it just tests for read permission instead
fchmod	not implemented
chown, fchown	not implemented (make no sense on a DOS file system)
umask	not implemented
mkfifo	not implemented
kill	partially implemented (since 4.00.0): only the sigkill signal is implemented
pause	not implemented (no inter-process signals in Windows)
alarm	not implemented
times	partially implemented, will not report timings for child processes
getitimer, setitimer	not implemented
getuid, geteuid, getgid, getegid	always return 1
getgroups	always returns [\|1\|] (since 2.00)
setuid, setgid, setgroups	not implemented
getpwnam, getpwuid	always raise Not_found
getgrnam, getgrgid	always raise Not_found
type socket_domain	PF_INET is fully supported; PF_INET6 is fully supported (since 4.01.0); PF_UNIX is not supported
establish_server	not implemented; use threads
terminal functions (tc*)	not implemented