\chapter{The unix library: Unix system calls}
%HEVEA\cutname{libunix.html}
\label{c:unix}

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.

\ifouthtml
\begin{linklist}
\libdocitem{Unix}{Unix system calls}
\libdocitem{UnixLabels}{Labeled Unix system calls}
\end{linklist}
\fi

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:
\begin{alltt}
        ocamlc \var{other options} -I +unix unix.cma \var{other files}
        ocamlopt \var{other options}  -I +unix unix.cmxa \var{other files}
\end{alltt}
For interactive use of the "unix" library, do:
\begin{alltt}
        ocamlmktop -o mytop -I +unix unix.cma
        ./mytop
\end{alltt}
or (if dynamic linking of C libraries is supported on your platform),
start "ocaml" and type

\begin{caml_example*}{toplevel}
#directory "+unix";;
#load "unix.cma";;
\end{caml_example*}

\begin{latexonly}
\begin{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.
\end{windows}

\begin{linklist}
\libdocitem{Unix}{Unix system calls}
\end{linklist}

\section{UnixLabels}{Module \texttt{UnixLabels}: labelized version of the interface}
\index{UnixLabels (module)@\verb~UnixLabels~ (module)}%

This module is identical to "Unix"~(\ref{Unix}), and only differs by
the addition of labels. You may see these labels directly by looking
at "unixLabels.mli", or by using the "ocamlbrowser" tool.
\newpage
\end{latexonly}

\begin{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.
\end{windows}

\begin{tableau}{|l|p{8cm}|}{Functions}{Comment}
\entree{"fork"}{not implemented, use "create_process" or threads}
\entree{"wait"}{not implemented, use "waitpid"}
\entree{"waitpid"}{can only wait for a given PID, not any child process}
\entree{"getppid"}{not implemented (meaningless under Windows)}
\entree{"nice"}{not implemented}
\entree{"truncate", "ftruncate"}{implemented (since 4.10.0)}
\entree{"link"}{implemented (since 3.02)}
\entree{"fchmod"}{not implemented}
\entree{"chown", "fchown"}{not implemented (make no sense on a DOS
file system)}
\entree{"umask"}{not implemented}
\entree{"access"}{execute permission "X_OK" cannot be tested,
  it just tests for read permission instead}
\entree{"chroot"}{not implemented}
\entree{"mkfifo"}{not implemented}
\entree{"symlink", "readlink"}{implemented (since 4.03.0)}
\entree{"kill"}{partially implemented (since 4.00.0): only the "sigkill" signal
is implemented}
\entree{"sigprocmask", "sigpending", "sigsuspend"}{not implemented (no inter-process signals on Windows}
\entree{"pause"}{not implemented (no inter-process signals in Windows)}
\entree{"alarm"}{not implemented}
\entree{"times"}{partially implemented, will not report timings for child
processes}
\entree{"getitimer", "setitimer"}{not implemented}
\entree{"getuid", "geteuid", "getgid", "getegid"}{always return 1}
\entree{"setuid", "setgid", "setgroups", "initgroups"}{not implemented}
\entree{"getgroups"}{always returns "[|1|]" (since 2.00)}
\entree{"getpwnam", "getpwuid"}{always raise "Not_found"}
\entree{"getgrnam", "getgrgid"}{always raise "Not_found"}
\entree{type "socket_domain"}{"PF_INET" is fully supported;
"PF_INET6" is fully supported (since 4.01.0); "PF_UNIX" is supported since 4.14.0, but only works on Windows 10 1803 and later.}
\entree{"establish_server"}{not implemented; use threads}
\entree{terminal functions ("tc*")}{not implemented}
\entree{"setsid"}{not implemented}
\end{tableau}