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Unix(3) 				  OCaml library 				  Unix(3)

NAME
       Unix - Interface to the Unix system

Module
       Module	Unix

Documentation
       Module Unix
	: sig end

       Interface to the Unix system

       === Error report ===

       type error =
	| E2BIG  (* Argument list too long *)
	| EACCES  (* Permission denied *)
	| EAGAIN  (* Resource temporarily unavailable; try again *)
	| EBADF  (* Bad file descriptor *)
	| EBUSY  (* Resource unavailable *)
	| ECHILD  (* No child process *)
	| EDEADLK  (* Resource deadlock would occur *)
	| EDOM	(* Domain error for math functions, etc. *)
	| EEXIST  (* File exists *)
	| EFAULT  (* Bad address *)
	| EFBIG  (* File too large *)
	| EINTR  (* Function interrupted by signal *)
	| EINVAL  (* Invalid argument *)
	| EIO  (* Hardware I/O error *)
	| EISDIR  (* Is a directory *)
	| EMFILE  (* Too many open files by the process *)
	| EMLINK  (* Too many links *)
	| ENAMETOOLONG	(* Filename too long *)
	| ENFILE  (* Too many open files in the system *)
	| ENODEV  (* No such device *)
	| ENOENT  (* No such file or directory *)
	| ENOEXEC  (* Not an executable file *)
	| ENOLCK  (* No locks available *)
	| ENOMEM  (* Not enough memory *)
	| ENOSPC  (* No space left on device *)
	| ENOSYS  (* Function not supported *)
	| ENOTDIR  (* Not a directory *)
	| ENOTEMPTY  (* Directory not empty *)
	| ENOTTY  (* Inappropriate I/O control operation *)
	| ENXIO  (* No such device or address *)
	| EPERM  (* Operation not permitted *)
	| EPIPE  (* Broken pipe *)
	| ERANGE  (* Result too large *)
	| EROFS  (* Read-only file system *)
	| ESPIPE  (* Invalid seek e.g. on a pipe *)
	| ESRCH  (* No such process *)
	| EXDEV  (* Invalid link *)
	| EWOULDBLOCK  (* Operation would block *)
	| EINPROGRESS  (* Operation now in progress *)
	| EALREADY  (* Operation already in progress *)
	| ENOTSOCK  (* Socket operation on non-socket *)
	| EDESTADDRREQ	(* Destination address required *)
	| EMSGSIZE  (* Message too long *)
	| EPROTOTYPE  (* Protocol wrong type for socket *)
	| ENOPROTOOPT  (* Protocol not available *)
	| EPROTONOSUPPORT  (* Protocol not supported *)
	| ESOCKTNOSUPPORT  (* Socket type not supported *)
	| EOPNOTSUPP  (* Operation not supported on socket *)
	| EPFNOSUPPORT	(* Protocol family not supported *)
	| EAFNOSUPPORT	(* Address family not supported by protocol family *)
	| EADDRINUSE  (* Address already in use *)
	| EADDRNOTAVAIL  (* Can't assign requested address *)
	| ENETDOWN  (* Network is down *)
	| ENETUNREACH  (* Network is unreachable *)
	| ENETRESET  (* Network dropped connection on reset *)
	| ECONNABORTED	(* Software caused connection abort *)
	| ECONNRESET  (* Connection reset by peer *)
	| ENOBUFS  (* No buffer space available *)
	| EISCONN  (* Socket is already connected *)
	| ENOTCONN  (* Socket is not connected *)
	| ESHUTDOWN  (* Can't send after socket shutdown *)
	| ETOOMANYREFS	(* Too many references: can't splice *)
	| ETIMEDOUT  (* Connection timed out *)
	| ECONNREFUSED	(* Connection refused *)
	| EHOSTDOWN  (* Host is down *)
	| EHOSTUNREACH	(* No route to host *)
	| ELOOP  (* Too many levels of symbolic links *)
	| EOVERFLOW  (* File size or position not representable *)
	| EUNKNOWNERR of int  (* Unknown error *)

       The  type of error codes.  Errors defined in the POSIX standard and additional errors from
       UNIX98 and BSD.	All other errors are mapped to EUNKNOWNERR.

       exception Unix_error of error * string * string

       Raised by the system calls below when an error is encountered.  The first component is the
       error  code;  the second component is the function name; the third component is the string
       parameter to the function, if it has one, or the empty string otherwise.

       val error_message : error -> string

       Return a string describing the given error code.

       val handle_unix_error : ('a -> 'b) -> 'a -> 'b

       handle_unix_error f x applies f to x and returns the result.  If the exception  Unix_error
       is raised, it prints a message describing the error and exits with code 2.

       === Access to the process environment ===

       val environment : unit -> string array

       Return the process environment, as an array of strings with the format ``variable=value''.

       val getenv : string -> string

       Return  the  value associated to a variable in the process environment. Raise Not_found if
       the variable is unbound.  (This function is identical to Sys.getenv .)

       val putenv : string -> string -> unit

       Unix.putenv name value sets the value associated to a variable in the process environment.
       name is the name of the environment variable, and value its new associated value.

       === Process handling ===

       type process_status =
	| WEXITED of int  (* The process terminated normally by exit ; the argument is the return
       code. *)
	| WSIGNALED of int  (* The process was killed by a signal; the	argument  is  the  signal
       number. *)
	|  WSTOPPED  of  int   (* The process was stopped by a signal; the argument is the signal
       number. *)

       The termination status of a process.  See module Sys for the definitions of  the  standard
       signal numbers.	Note that they are not the numbers used by the OS.

       type wait_flag =
	|  WNOHANG   (*  do not block if no child has died yet, but immediately return with a pid
       equal to 0. *)
	| WUNTRACED  (* report also the children that receive stop signals. *)

       Flags for Unix.waitpid .

       val execv : string -> string array -> 'a

       execv prog args execute the program in file prog , with the arguments args , and the  cur-
       rent  process  environment.   These execv* functions never return: on success, the current
       program is replaced by the new one; on failure, a Unix.Unix_error exception is raised.

       val execve : string -> string array -> string array -> 'a

       Same as Unix.execv , except that the third argument provides the environment to	the  pro-
       gram executed.

       val execvp : string -> string array -> 'a

       Same as Unix.execv , except that the program is searched in the path.

       val execvpe : string -> string array -> string array -> 'a

       Same as Unix.execve , except that the program is searched in the path.

       val fork : unit -> int

       Fork  a new process. The returned integer is 0 for the child process, the pid of the child
       process for the parent process.

       val wait : unit -> int * process_status

       Wait until one of the children processes die, and return its pid and termination status.

       val waitpid : wait_flag list -> int -> int * process_status

       Same as Unix.wait , but waits for the child process whose pid is given.	A pid of -1 means
       wait  for any child.  A pid of 0 means wait for any child in the same process group as the
       current process.  Negative pid arguments represent process groups.  The	list  of  options
       indicates  whether  waitpid  should  return  immediately  without  waiting, or also report
       stopped children.

       val system : string -> process_status

       Execute the given command, wait until it terminates, and return	its  termination  status.
       The  string  is	interpreted  by the shell /bin/sh and therefore can contain redirections,
       quotes, variables, etc. The result WEXITED 127 indicates that the shell couldn't  be  exe-
       cuted.

       val getpid : unit -> int

       Return the pid of the process.

       val getppid : unit -> int

       Return the pid of the parent process.

       val nice : int -> int

       Change  the process priority. The integer argument is added to the ``nice'' value. (Higher
       values of the ``nice'' value mean lower priorities.) Return the new nice value.

       === Basic file input/output ===

       type file_descr

       The abstract type of file descriptors.

       val stdin : file_descr

       File descriptor for standard input.

       val stdout : file_descr

       File descriptor for standard output.

       val stderr : file_descr

       File descriptor for standard error.

       type open_flag =
	| O_RDONLY  (* Open for reading *)
	| O_WRONLY  (* Open for writing *)
	| O_RDWR  (* Open for reading and writing *)
	| O_NONBLOCK  (* Open in non-blocking mode *)
	| O_APPEND  (* Open for append *)
	| O_CREAT  (* Create if nonexistent *)
	| O_TRUNC  (* Truncate to 0 length if existing *)
	| O_EXCL  (* Fail if existing *)
	| O_NOCTTY  (* Don't make this dev a controlling tty *)
	| O_DSYNC  (* Writes complete as `Synchronised I/O data integrity completion' *)
	| O_SYNC  (* Writes complete as `Synchronised I/O file integrity completion' *)
	| O_RSYNC  (* Reads complete as writes (depending on O_SYNC/O_DSYNC) *)
	| O_SHARE_DELETE  (* Windows only: allow the file to be deleted while still open *)

       The flags to Unix.openfile .

       type file_perm = int

       The type of file access rights, e.g.  0o640 is read and write for user,	read  for  group,
       none for others

       val openfile : string -> open_flag list -> file_perm -> file_descr

       Open the named file with the given flags. Third argument is the permissions to give to the
       file if it is created. Return a file descriptor on the named file.

       val close : file_descr -> unit

       Close a file descriptor.

       val read : file_descr -> string -> int -> int -> int

       read fd buff ofs len reads len characters from descriptor fd , storing them in string buff
       , starting at position ofs in string buff . Return the number of characters actually read.

       val write : file_descr -> string -> int -> int -> int

       write  fd  buff	ofs  len writes len characters to descriptor fd , taking them from string
       buff , starting at position ofs in string buff . Return the number of characters  actually
       written.  write repeats the writing operation until all characters have been written or an
       error occurs.

       val single_write : file_descr -> string -> int -> int -> int

       Same as write , but attempts to write only once.  Thus, if an error  occurs,  single_write
       guarantees that no data has been written.

       === Interfacing with the standard input/output library ===

       val in_channel_of_descr : file_descr -> Pervasives.in_channel

       Create  an  input  channel reading from the given descriptor.  The channel is initially in
       binary mode; use set_binary_mode_in ic false if text mode is desired.

       val out_channel_of_descr : file_descr -> Pervasives.out_channel

       Create an output channel writing on the given descriptor.  The  channel	is  initially  in
       binary mode; use set_binary_mode_out oc false if text mode is desired.

       val descr_of_in_channel : Pervasives.in_channel -> file_descr

       Return the descriptor corresponding to an input channel.

       val descr_of_out_channel : Pervasives.out_channel -> file_descr

       Return the descriptor corresponding to an output channel.

       === Seeking and truncating ===

       type seek_command =
	| SEEK_SET  (* indicates positions relative to the beginning of the file *)
	| SEEK_CUR  (* indicates positions relative to the current position *)
	| SEEK_END  (* indicates positions relative to the end of the file *)

       Positioning modes for Unix.lseek .

       val lseek : file_descr -> int -> seek_command -> int

       Set the current position for a file descriptor

       val truncate : string -> int -> unit

       Truncates the named file to the given size.

       val ftruncate : file_descr -> int -> unit

       Truncates the file corresponding to the given descriptor to the given size.

       === File status ===

       type file_kind =
	| S_REG  (* Regular file *)
	| S_DIR  (* Directory *)
	| S_CHR  (* Character device *)
	| S_BLK  (* Block device *)
	| S_LNK  (* Symbolic link *)
	| S_FIFO  (* Named pipe *)
	| S_SOCK  (* Socket *)

       type stats = {
	st_dev : int ;	(* Device number *)
	st_ino : int ;	(* Inode number *)
	st_kind : file_kind ;  (* Kind of the file *)
	st_perm : file_perm ;  (* Access rights *)
	st_nlink : int ;  (* Number of links *)
	st_uid : int ;	(* User id of the owner *)
	st_gid : int ;	(* Group ID of the file's group *)
	st_rdev : int ;  (* Device minor number *)
	st_size : int ;  (* Size in bytes *)
	st_atime : float ;  (* Last access time *)
	st_mtime : float ;  (* Last modification time *)
	st_ctime : float ;  (* Last status change time *)
	}

       The information returned by the Unix.stat calls.

       val stat : string -> stats

       Return the information for the named file.

       val lstat : string -> stats

       Same  as  Unix.stat  , but in case the file is a symbolic link, return the information for
       the link itself.

       val fstat : file_descr -> stats

       Return the information for the file associated with the given descriptor.

       val isatty : file_descr -> bool

       Return true if the given file descriptor refers to a terminal  or  console  window,  false
       otherwise.

       === File operations on large files ===

       module LargeFile : sig end

       File operations on large files.	This sub-module provides 64-bit variants of the functions
       Unix.lseek (for positioning a file  descriptor),  Unix.truncate	and  Unix.ftruncate  (for
       changing  the  size  of	a file), and Unix.stat , Unix.lstat and Unix.fstat (for obtaining
       information on files).  These alternate functions represent positions and sizes by  64-bit
       integers (type int64 ) instead of regular integers (type int ), thus allowing operating on
       files whose sizes are greater than max_int .

       === Operations on file names ===

       val unlink : string -> unit

       Removes the named file

       val rename : string -> string -> unit

       rename old new changes the name of a file from old to new .

       val link : string -> string -> unit

       link source dest creates a hard link named dest to the file named source .

       === File permissions and ownership ===

       type access_permission =
	| R_OK	(* Read permission *)
	| W_OK	(* Write permission *)
	| X_OK	(* Execution permission *)
	| F_OK	(* File exists *)

       Flags for the Unix.access call.

       val chmod : string -> file_perm -> unit

       Change the permissions of the named file.

       val fchmod : file_descr -> file_perm -> unit

       Change the permissions of an opened file.

       val chown : string -> int -> int -> unit

       Change the owner uid and owner gid of the named file.

       val fchown : file_descr -> int -> int -> unit

       Change the owner uid and owner gid of an opened file.

       val umask : int -> int

       Set the process's file mode creation mask, and return the previous mask.

       val access : string -> access_permission list -> unit

       Check that the process has the given permissions over the  named  file.	Raise  Unix_error
       otherwise.

       === Operations on file descriptors ===

       val dup : file_descr -> file_descr

       Return a new file descriptor referencing the same file as the given descriptor.

       val dup2 : file_descr -> file_descr -> unit

       dup2 fd1 fd2 duplicates fd1 to fd2 , closing fd2 if already opened.

       val set_nonblock : file_descr -> unit

       Set the ``non-blocking'' flag on the given descriptor.  When the non-blocking flag is set,
       reading on a descriptor on which there is temporarily no data available raises the  EAGAIN
       or EWOULDBLOCK error instead of blocking; writing on a descriptor on which there is tempo-
       rarily no room for writing also raises EAGAIN or EWOULDBLOCK .

       val clear_nonblock : file_descr -> unit

       Clear the ``non-blocking'' flag on the given descriptor.  See Unix.set_nonblock .

       val set_close_on_exec : file_descr -> unit

       Set  the  ``close-on-exec''  flag  on  the  given  descriptor.	A  descriptor  with   the
       close-on-exec flag is automatically closed when the current process starts another program
       with one of the exec functions.

       val clear_close_on_exec : file_descr -> unit

       Clear the ``close-on-exec'' flag on the given descriptor.  See Unix.set_close_on_exec .

       === Directories ===

       val mkdir : string -> file_perm -> unit

       Create a directory with the given permissions.

       val rmdir : string -> unit

       Remove an empty directory.

       val chdir : string -> unit

       Change the process working directory.

       val getcwd : unit -> string

       Return the name of the current working directory.

       val chroot : string -> unit

       Change the process root directory.

       type dir_handle

       The type of descriptors over opened directories.

       val opendir : string -> dir_handle

       Open a descriptor on a directory

       val readdir : dir_handle -> string

       Return the next entry in a directory.

       Raises End_of_file when the end of the directory has been reached.

       val rewinddir : dir_handle -> unit

       Reposition the descriptor to the beginning of the directory

       val closedir : dir_handle -> unit

       Close a directory descriptor.

       === Pipes and redirections ===

       val pipe : unit -> file_descr * file_descr

       Create a pipe. The first component of the result is opened for reading, that's the exit to
       the pipe. The second component is opened for writing, that's the entrance to the pipe.

       val mkfifo : string -> file_perm -> unit

       Create a named pipe with the given permissions.

       === High-level process and redirection management ===

       val  create_process  : string -> string array -> file_descr -> file_descr -> file_descr ->
       int

       create_process prog args new_stdin new_stdout new_stderr forks a new process that executes
       the  program  in  file prog , with arguments args . The pid of the new process is returned
       immediately; the new process executes concurrently with the current process.  The standard
       input and outputs of the new process are connected to the descriptors new_stdin , new_std-
       out and new_stderr .  Passing e.g.  stdout for new_stdout  prevents  the  redirection  and
       causes  the new process to have the same standard output as the current process.  The exe-
       cutable file prog is searched in the path.  The new process has the  same  environment  as
       the current process.

       val  create_process_env	:  string  ->  string  array  ->  string  array  -> file_descr ->
       file_descr -> file_descr -> int

       create_process_env prog args  env  new_stdin  new_stdout  new_stderr  works  as	Unix.cre-
       ate_process  ,  except that the extra argument env specifies the environment passed to the
       program.

       val open_process_in : string -> Pervasives.in_channel

       High-level pipe and process management. This function runs the given command  in  parallel
       with  the  program.  The standard output of the command is redirected to a pipe, which can
       be read via the returned input channel.	The command is interpreted by the  shell  /bin/sh
       (cf.  system ).

       val open_process_out : string -> Pervasives.out_channel

       Same  as  Unix.open_process_in , but redirect the standard input of the command to a pipe.
       Data written to the returned output channel is sent to the standard input of the  command.
       Warning: writes on output channels are buffered, hence be careful to call Pervasives.flush
       at the right times to ensure correct synchronization.

       val open_process : string -> Pervasives.in_channel * Pervasives.out_channel

       Same as Unix.open_process_out , but redirects both the standard input and standard  output
       of the command to pipes connected to the two returned channels.	The input channel is con-
       nected to the output of the command, and the output channel to the input of the command.

       val  open_process_full  :  string  ->  string  array  ->  Pervasives.in_channel	*  Perva-
       sives.out_channel * Pervasives.in_channel

       Similar to Unix.open_process , but the second argument specifies the environment passed to
       the command.  The result is a triple of channels connected respectively	to  the  standard
       output, standard input, and standard error of the command.

       val close_process_in : Pervasives.in_channel -> process_status

       Close  channels opened by Unix.open_process_in , wait for the associated command to termi-
       nate, and return its termination status.

       val close_process_out : Pervasives.out_channel -> process_status

       Close channels opened by Unix.open_process_out , wait for the associated command to termi-
       nate, and return its termination status.

       val close_process : Pervasives.in_channel * Pervasives.out_channel -> process_status

       Close channels opened by Unix.open_process , wait for the associated command to terminate,
       and return its termination status.

       val  close_process_full	:  Pervasives.in_channel  *   Pervasives.out_channel   *   Perva-
       sives.in_channel -> process_status

       Close  channels opened by Unix.open_process_full , wait for the associated command to ter-
       minate, and return its termination status.

       === Symbolic links ===

       val symlink : string -> string -> unit

       symlink source dest creates the file dest as a symbolic link to the file source .

       val readlink : string -> string

       Read the contents of a link.

       === Polling ===

       val select : file_descr list -> file_descr list -> file_descr list -> float ->  file_descr
       list * file_descr list * file_descr list

       Wait  until  some input/output operations become possible on some channels. The three list
       arguments are, respectively, a set of descriptors to check for reading  (first  argument),
       for writing (second argument), or for exceptional conditions (third argument).  The fourth
       argument is the maximal timeout, in seconds; a negative fourth argument means  no  timeout
       (unbounded  wait).   The  result is composed of three sets of descriptors: those ready for
       reading (first component), ready for writing (second component), and over which an  excep-
       tional condition is pending (third component).

       === Locking ===

       type lock_command =
	| F_ULOCK  (* Unlock a region *)
	| F_LOCK  (* Lock a region for writing, and block if already locked *)
	| F_TLOCK  (* Lock a region for writing, or fail if already locked *)
	| F_TEST  (* Test a region for other process locks *)
	| F_RLOCK  (* Lock a region for reading, and block if already locked *)
	| F_TRLOCK  (* Lock a region for reading, or fail if already locked *)

       Commands for Unix.lockf .

       val lockf : file_descr -> lock_command -> int -> unit

       lockf  fd cmd size puts a lock on a region of the file opened as fd . The region starts at
       the current read/write position for fd (as set by Unix.lseek ),	and  extends  size  bytes
       forward	if  size  is positive, size bytes backwards if size is negative, or to the end of
       the file if size is zero.  A write lock prevents any other process from acquiring  a  read
       or  write  lock	on  the  region.  A read lock prevents any other process from acquiring a
       write lock on the region, but lets other processes acquire read locks on it.

       The F_LOCK and F_TLOCK commands attempts to put a write lock on the specified region.  The
       F_RLOCK and F_TRLOCK commands attempts to put a read lock on the specified region.  If one
       or several locks put by another process prevent the current  process  from  acquiring  the
       lock,  F_LOCK  and F_RLOCK block until these locks are removed, while F_TLOCK and F_TRLOCK
       fail immediately with an exception.   The  F_ULOCK  removes  whatever  locks  the  current
       process	has  on  the specified region.	Finally, the F_TEST command tests whether a write
       lock can be acquired on the specified region, without actually putting a lock.  It returns
       immediately if successful, or fails otherwise.

       ===  Signals Note: installation of signal handlers is performed via the functions Sys.sig-
       nal and Sys.set_signal. ===

       val kill : int -> int -> unit

       kill pid sig sends signal number sig to the process with id pid .

       type sigprocmask_command =
	| SIG_SETMASK
	| SIG_BLOCK
	| SIG_UNBLOCK

       val sigprocmask : sigprocmask_command -> int list -> int list

       sigprocmask cmd sigs changes the set of blocked signals.  If cmd is SIG_SETMASK ,  blocked
       signals are set to those in the list sigs .  If cmd is SIG_BLOCK , the signals in sigs are
       added to the set of blocked signals.  If cmd is SIG_UNBLOCK ,  the  signals  in	sigs  are
       removed	from  the  set	of  blocked  signals.	sigprocmask returns the set of previously
       blocked signals.

       val sigpending : unit -> int list

       Return the set of blocked signals that are currently pending.

       val sigsuspend : int list -> unit

       sigsuspend sigs atomically sets the blocked signals to sigs and waits for  a  non-ignored,
       non-blocked  signal  to	be  delivered.	On return, the blocked signals are reset to their
       initial value.

       val pause : unit -> unit

       Wait until a non-ignored, non-blocked signal is delivered.

       === Time functions ===

       type process_times = {
	tms_utime : float ;  (* User time for the process *)
	tms_stime : float ;  (* System time for the process *)
	tms_cutime : float ;  (* User time for the children processes *)
	tms_cstime : float ;  (* System time for the children processes *)
	}

       The execution times (CPU times) of a process.

       type tm = {
	tm_sec : int ;	(* Seconds 0..60 *)
	tm_min : int ;	(* Minutes 0..59 *)
	tm_hour : int ;  (* Hours 0..23 *)
	tm_mday : int ;  (* Day of month 1..31 *)
	tm_mon : int ;	(* Month of year 0..11 *)
	tm_year : int ;  (* Year - 1900 *)
	tm_wday : int ;  (* Day of week (Sunday is 0) *)
	tm_yday : int ;  (* Day of year 0..365 *)
	tm_isdst : bool ;  (* Daylight time savings in effect *)
	}

       The type representing wallclock time and calendar date.

       val time : unit -> float

       Return the current time since 00:00:00 GMT, Jan. 1, 1970, in seconds.

       val gettimeofday : unit -> float

       Same as Unix.time , but with resolution better than 1 second.

       val gmtime : float -> tm

       Convert a time in seconds, as returned by Unix.time , into a date and a time. Assumes  UTC
       (Coordinated Universal Time), also known as GMT.

       val localtime : float -> tm

       Convert	a time in seconds, as returned by Unix.time , into a date and a time. Assumes the
       local time zone.

       val mktime : tm -> float * tm

       Convert a date and time, specified by the tm argument, into a time in seconds, as returned
       by  Unix.time .	The tm_isdst , tm_wday and tm_yday fields of tm are ignored.  Also return
       a normalized copy of the given tm record, with the tm_wday , tm_yday , and tm_isdst fields
       recomputed from the other fields, and the other fields normalized (so that, e.g., 40 Octo-
       ber is changed into 9 November).  The tm argument is interpreted in the local time zone.

       val alarm : int -> int

       Schedule a SIGALRM signal after the given number of seconds.

       val sleep : int -> unit

       Stop execution for the given number of seconds.

       val times : unit -> process_times

       Return the execution times of the process.

       val utimes : string -> float -> float -> unit

       Set the last access time (second arg) and last modification time (third arg) for  a  file.
       Times  are  expressed in seconds from 00:00:00 GMT, Jan. 1, 1970.  A time of 0.0 is inter-
       preted as the current time.

       type interval_timer =
	| ITIMER_REAL  (* decrements in real time, and sends the signal SIGALRM when expired. *)
	| ITIMER_VIRTUAL  (* decrements  in  process  virtual  time,  and  sends  SIGVTALRM  when
       expired. *)
	|  ITIMER_PROF	 (*  (for profiling) decrements both when the process is running and when
       the system is running on behalf of the process; it sends SIGPROF when expired. *)

       The three kinds of interval timers.

       type interval_timer_status = {
	it_interval : float ;  (* Period *)
	it_value : float ;  (* Current value of the timer *)
	}

       The type describing the status of an interval timer

       val getitimer : interval_timer -> interval_timer_status

       Return the current status of the given interval timer.

       val setitimer : interval_timer -> interval_timer_status -> interval_timer_status

       setitimer t s sets the interval timer t and returns its previous status. The s argument is
       interpreted as follows: s.it_value , if nonzero, is the time to the next timer expiration;
       s.it_interval , if nonzero, specifies a value to be used in reloading  it_value	when  the
       timer  expires.	 Setting  s.it_value to zero disable the timer.  Setting s.it_interval to
       zero causes the timer to be disabled after its next expiration.

       === User id, group id ===

       val getuid : unit -> int

       Return the user id of the user executing the process.

       val geteuid : unit -> int

       Return the effective user id under which the process runs.

       val setuid : int -> unit

       Set the real user id and effective user id for the process.

       val getgid : unit -> int

       Return the group id of the user executing the process.

       val getegid : unit -> int

       Return the effective group id under which the process runs.

       val setgid : int -> unit

       Set the real group id and effective group id for the process.

       val getgroups : unit -> int array

       Return the list of groups to which the user executing the process belongs.

       val setgroups : int array -> unit

       setgroups groups sets the supplementary group IDs for  the  calling  process.  Appropriate
       privileges are required.

       val initgroups : string -> int -> unit

       initgroups  user  group	initializes  the  group access list by reading the group database
       /etc/group and using all groups of which user is a member. The additional group	group  is
       also added to the list.

       type passwd_entry = {
	pw_name : string ;
	pw_passwd : string ;
	pw_uid : int ;
	pw_gid : int ;
	pw_gecos : string ;
	pw_dir : string ;
	pw_shell : string ;
	}

       Structure of entries in the passwd database.

       type group_entry = {
	gr_name : string ;
	gr_passwd : string ;
	gr_gid : int ;
	gr_mem : string array ;
	}

       Structure of entries in the groups database.

       val getlogin : unit -> string

       Return the login name of the user executing the process.

       val getpwnam : string -> passwd_entry

       Find an entry in passwd with the given name, or raise Not_found .

       val getgrnam : string -> group_entry

       Find an entry in group with the given name, or raise Not_found .

       val getpwuid : int -> passwd_entry

       Find an entry in passwd with the given user id, or raise Not_found .

       val getgrgid : int -> group_entry

       Find an entry in group with the given group id, or raise Not_found .

       === Internet addresses ===

       type inet_addr

       The abstract type of Internet addresses.

       val inet_addr_of_string : string -> inet_addr

       Conversion from the printable representation of an Internet address to its internal repre-
       sentation.   The  argument  string  consists  of  4  numbers  separated	 by   periods	(
       XXX.YYY.ZZZ.TTT	)  for	IPv4  addresses, and up to 8 numbers separated by colons for IPv6
       addresses.  Raise Failure when given a string that does not match these formats.

       val string_of_inet_addr : inet_addr -> string

       Return	the   printable   representation   of	the   given   Internet	 address.     See
       Unix.inet_addr_of_string for a description of the printable representation.

       val inet_addr_any : inet_addr

       A  special  IPv4 address, for use only with bind , representing all the Internet addresses
       that the host machine possesses.

       val inet_addr_loopback : inet_addr

       A special IPv4 address representing the host machine ( 127.0.0.1 ).

       val inet6_addr_any : inet_addr

       A special IPv6 address, for use only with bind , representing all the  Internet	addresses
       that the host machine possesses.

       val inet6_addr_loopback : inet_addr

       A special IPv6 address representing the host machine ( ::1 ).

       === Sockets ===

       type socket_domain =
	| PF_UNIX  (* Unix domain *)
	| PF_INET  (* Internet domain (IPv4) *)
	| PF_INET6  (* Internet domain (IPv6) *)

       The type of socket domains.  Not all platforms support IPv6 sockets (type PF_INET6 ).

       type socket_type =
	| SOCK_STREAM  (* Stream socket *)
	| SOCK_DGRAM  (* Datagram socket *)
	| SOCK_RAW  (* Raw socket *)
	| SOCK_SEQPACKET  (* Sequenced packets socket *)

       The type of socket kinds, specifying the semantics of communications.

       type sockaddr =
	| ADDR_UNIX of string
	|  ADDR_INET  of  inet_addr  * int  (* The type of socket addresses.  ADDR_UNIX name is a
       socket  address	in  the  Unix  domain;	name  is  a  file  name  in  the   file   system.
       ADDR_INET(addr,port)  is  a  socket  address  in the Internet domain; addr is the Internet
       address of the machine, and port is the port number. *)

       val socket : socket_domain -> socket_type -> int -> file_descr

       Create a new socket in the given domain, and with the given kind. The  third  argument  is
       the protocol type; 0 selects the default protocol for that kind of sockets.

       val domain_of_sockaddr : sockaddr -> socket_domain

       Return the socket domain adequate for the given socket address.

       val socketpair : socket_domain -> socket_type -> int -> file_descr * file_descr

       Create a pair of unnamed sockets, connected together.

       val accept : file_descr -> file_descr * sockaddr

       Accept  connections  on the given socket. The returned descriptor is a socket connected to
       the client; the returned address is the address of the connecting client.

       val bind : file_descr -> sockaddr -> unit

       Bind a socket to an address.

       val connect : file_descr -> sockaddr -> unit

       Connect a socket to an address.

       val listen : file_descr -> int -> unit

       Set up a socket for receiving connection requests. The integer  argument  is  the  maximal
       number of pending requests.

       type shutdown_command =
	| SHUTDOWN_RECEIVE  (* Close for receiving *)
	| SHUTDOWN_SEND  (* Close for sending *)
	| SHUTDOWN_ALL	(* Close both *)

       The type of commands for shutdown .

       val shutdown : file_descr -> shutdown_command -> unit

       Shutdown  a socket connection.  SHUTDOWN_SEND as second argument causes reads on the other
       end of the connection to return an end-of-file condition.  SHUTDOWN_RECEIVE causes  writes
       on the other end of the connection to return a closed pipe condition ( SIGPIPE signal).

       val getsockname : file_descr -> sockaddr

       Return the address of the given socket.

       val getpeername : file_descr -> sockaddr

       Return the address of the host connected to the given socket.

       type msg_flag =
	| MSG_OOB
	| MSG_DONTROUTE
	| MSG_PEEK  (* The flags for Unix.recv , Unix.recvfrom , Unix.send and Unix.sendto . *)

       val recv : file_descr -> string -> int -> int -> msg_flag list -> int

       Receive data from a connected socket.

       val recvfrom : file_descr -> string -> int -> int -> msg_flag list -> int * sockaddr

       Receive data from an unconnected socket.

       val send : file_descr -> string -> int -> int -> msg_flag list -> int

       Send data over a connected socket.

       val sendto : file_descr -> string -> int -> int -> msg_flag list -> sockaddr -> int

       Send data over an unconnected socket.

       === Socket options ===

       type socket_bool_option =
	| SO_DEBUG  (* Record debugging information *)
	| SO_BROADCAST	(* Permit sending of broadcast messages *)
	| SO_REUSEADDR	(* Allow reuse of local addresses for bind *)
	| SO_KEEPALIVE	(* Keep connection active *)
	| SO_DONTROUTE	(* Bypass the standard routing algorithms *)
	| SO_OOBINLINE	(* Leave out-of-band data in line *)
	| SO_ACCEPTCONN  (* Report whether socket listening is enabled *)
	| TCP_NODELAY  (* Control the Nagle algorithm for TCP sockets *)
	| IPV6_ONLY  (* Forbid binding an IPv6 socket to an IPv4 address *)

       The  socket options that can be consulted with Unix.getsockopt and modified with Unix.set-
       sockopt .  These options have a boolean ( true / false ) value.

       type socket_int_option =
	| SO_SNDBUF  (* Size of send buffer *)
	| SO_RCVBUF  (* Size of received buffer *)
	| SO_ERROR  (* Deprecated.  Use Unix.getsockopt_error instead. *)
	| SO_TYPE  (* Report the socket type *)
	| SO_RCVLOWAT  (* Minimum number of bytes to process for input operations *)
	| SO_SNDLOWAT  (* Minimum number of bytes to process for output operations *)

       The socket options that can  be	consulted  with  Unix.getsockopt_int  and  modified  with
       Unix.setsockopt_int .  These options have an integer value.

       type socket_optint_option =
	|  SO_LINGER   (* Whether to linger on closed connections that have data present, and for
       how long (in seconds) *)

       The socket options that can be consulted with  Unix.getsockopt_optint  and  modified  with
       Unix.setsockopt_optint  .  These options have a value of type int option , with None mean-
       ing ``disabled''.

       type socket_float_option =
	| SO_RCVTIMEO  (* Timeout for input operations *)
	| SO_SNDTIMEO  (* Timeout for output operations *)

       The socket options that can be consulted  with  Unix.getsockopt_float  and  modified  with
       Unix.setsockopt_float  .  These options have a floating-point value representing a time in
       seconds.  The value 0 means infinite timeout.

       val getsockopt : file_descr -> socket_bool_option -> bool

       Return the current status of a boolean-valued option in the given socket.

       val setsockopt : file_descr -> socket_bool_option -> bool -> unit

       Set or clear a boolean-valued option in the given socket.

       val getsockopt_int : file_descr -> socket_int_option -> int

       Same as Unix.getsockopt for an integer-valued socket option.

       val setsockopt_int : file_descr -> socket_int_option -> int -> unit

       Same as Unix.setsockopt for an integer-valued socket option.

       val getsockopt_optint : file_descr -> socket_optint_option -> int option

       Same as Unix.getsockopt for a socket option whose value is an int option .

       val setsockopt_optint : file_descr -> socket_optint_option -> int option -> unit

       Same as Unix.setsockopt for a socket option whose value is an int option .

       val getsockopt_float : file_descr -> socket_float_option -> float

       Same as Unix.getsockopt for a socket option whose value is a floating-point number.

       val setsockopt_float : file_descr -> socket_float_option -> float -> unit

       Same as Unix.setsockopt for a socket option whose value is a floating-point number.

       val getsockopt_error : file_descr -> error option

       Return the error condition associated with the given socket, and clear it.

       === High-level network connection functions ===

       val open_connection : sockaddr -> Pervasives.in_channel * Pervasives.out_channel

       Connect to a server at the given address.  Return a pair of buffered channels connected to
       the server.  Remember to call Pervasives.flush on the output channel at the right times to
       ensure correct synchronization.

       val shutdown_connection : Pervasives.in_channel -> unit

       ``Shut down'' a connection established with Unix.open_connection ; that	is,  transmit  an
       end-of-file condition to the server reading on the other side of the connection.

       val  establish_server : (Pervasives.in_channel -> Pervasives.out_channel -> unit) -> sock-
       addr -> unit

       Establish a server on the given address.  The function given as first argument  is  called
       for  each  connection with two buffered channels connected to the client. A new process is
       created for each connection. The function Unix.establish_server never returns normally.

       === Host and protocol databases ===

       type host_entry = {
	h_name : string ;
	h_aliases : string array ;
	h_addrtype : socket_domain ;
	h_addr_list : inet_addr array ;
	}

       Structure of entries in the hosts database.

       type protocol_entry = {
	p_name : string ;
	p_aliases : string array ;
	p_proto : int ;
	}

       Structure of entries in the protocols database.

       type service_entry = {
	s_name : string ;
	s_aliases : string array ;
	s_port : int ;
	s_proto : string ;
	}

       Structure of entries in the services database.

       val gethostname : unit -> string

       Return the name of the local host.

       val gethostbyname : string -> host_entry

       Find an entry in hosts with the given name, or raise Not_found .

       val gethostbyaddr : inet_addr -> host_entry

       Find an entry in hosts with the given address, or raise Not_found .

       val getprotobyname : string -> protocol_entry

       Find an entry in protocols with the given name, or raise Not_found .

       val getprotobynumber : int -> protocol_entry

       Find an entry in protocols with the given protocol number, or raise Not_found .

       val getservbyname : string -> string -> service_entry

       Find an entry in services with the given name, or raise Not_found .

       val getservbyport : int -> string -> service_entry

       Find an entry in services with the given service number, or raise Not_found .

       type addr_info = {
	ai_family : socket_domain ;  (* Socket domain *)
	ai_socktype : socket_type ;  (* Socket type *)
	ai_protocol : int ;  (* Socket protocol number *)
	ai_addr : sockaddr ;  (* Address *)
	ai_canonname : string ;  (* Canonical host name *)
	}

       Address information returned by Unix.getaddrinfo .

       type getaddrinfo_option =
	| AI_FAMILY of socket_domain  (* Impose the given socket domain *)
	| AI_SOCKTYPE of socket_type  (* Impose the given socket type *)
	| AI_PROTOCOL of int  (* Impose the given protocol *)
	| AI_NUMERICHOST  (* Do not call name resolver, expect numeric IP address *)
	| AI_CANONNAME	(* Fill the ai_canonname field of the result *)
	| AI_PASSIVE  (* Set address to ``any'' address for use with Unix.bind
	*)

       Options to Unix.getaddrinfo .

       val getaddrinfo : string -> string -> getaddrinfo_option list -> addr_info list

       getaddrinfo host service opts returns a list of Unix.addr_info records  describing  socket
       parameters  and addresses suitable for communicating with the given host and service.  The
       empty list is returned if the host or  service  names  are  unknown,  or  the  constraints
       expressed in opts cannot be satisfied.

       host  is  either  a  host name or the string representation of an IP address.  host can be
       given as the empty string; in this case, the ``any'' address or the  ``loopback''  address
       are  used,  depending whether opts contains AI_PASSIVE .  service is either a service name
       or the string representation of a port number.  service can be given as the empty  string;
       in  this  case,	the port field of the returned addresses is set to 0.  opts is a possibly
       empty list of options that allows the caller to force a	particular  socket  domain  (e.g.
       IPv6 only or IPv4 only) or a particular socket type (e.g. TCP only or UDP only).

       type name_info = {
	ni_hostname : string ;	(* Name or IP address of host *)
	ni_service : string ;
	}

       Name of service or port number

       === Host and service information returned by Unix.getnameinfo. ===

       type getnameinfo_option =
	| NI_NOFQDN  (* Do not qualify local host names *)
	| NI_NUMERICHOST  (* Always return host as IP address *)
	| NI_NAMEREQD  (* Fail if host name cannot be determined *)
	| NI_NUMERICSERV  (* Always return service as port number *)
	| NI_DGRAM  (* Consider the service as UDP-based instead of the default TCP *)

       Options to Unix.getnameinfo .

       val getnameinfo : sockaddr -> getnameinfo_option list -> name_info

       getnameinfo  addr  opts returns the host name and service name corresponding to the socket
       address addr .  opts is a possibly empty list of options that governs how these names  are
       obtained.  Raise Not_found if an error occurs.

       === Terminal interface ===

       ===  The following functions implement the POSIX standard terminal interface. They provide
       control over asynchronous communication ports and pseudo-terminals. Refer to  the  termios
       man page for a complete description. ===

       type terminal_io = {

       mutable c_ignbrk : bool ;  (* Ignore the break condition. *)

       mutable c_brkint : bool ;  (* Signal interrupt on break condition. *)

       mutable c_ignpar : bool ;  (* Ignore characters with parity errors. *)

       mutable c_parmrk : bool ;  (* Mark parity errors. *)

       mutable c_inpck : bool ;  (* Enable parity check on input. *)

       mutable c_istrip : bool ;  (* Strip 8th bit on input characters. *)

       mutable c_inlcr : bool ;  (* Map NL to CR on input. *)

       mutable c_igncr : bool ;  (* Ignore CR on input. *)

       mutable c_icrnl : bool ;  (* Map CR to NL on input. *)

       mutable c_ixon : bool ;	(* Recognize XON/XOFF characters on input. *)

       mutable c_ixoff : bool ;  (* Emit XON/XOFF chars to control input flow. *)

       mutable c_opost : bool ;  (* Enable output processing. *)

       mutable c_obaud : int ;	(* Output baud rate (0 means close connection). *)

       mutable c_ibaud : int ;	(* Input baud rate. *)

       mutable c_csize : int ;	(* Number of bits per character (5-8). *)

       mutable c_cstopb : int ;  (* Number of stop bits (1-2). *)

       mutable c_cread : bool ;  (* Reception is enabled. *)

       mutable c_parenb : bool ;  (* Enable parity generation and detection. *)

       mutable c_parodd : bool ;  (* Specify odd parity instead of even. *)

       mutable c_hupcl : bool ;  (* Hang up on last close. *)

       mutable c_clocal : bool ;  (* Ignore modem status lines. *)

       mutable c_isig : bool ;	(* Generate signal on INTR, QUIT, SUSP. *)

       mutable c_icanon : bool ;  (* Enable canonical processing (line buffering and editing) *)

       mutable c_noflsh : bool ;  (* Disable flush after INTR, QUIT, SUSP. *)

       mutable c_echo : bool ;	(* Echo input characters. *)

       mutable c_echoe : bool ;  (* Echo ERASE (to erase previous character). *)

       mutable c_echok : bool ;  (* Echo KILL (to erase the current line). *)

       mutable c_echonl : bool ;  (* Echo NL even if c_echo is not set. *)

       mutable c_vintr : char ;  (* Interrupt character (usually ctrl-C). *)

       mutable c_vquit : char ;  (* Quit character (usually ctrl-\). *)

       mutable c_verase : char ;  (* Erase character (usually DEL or ctrl-H). *)

       mutable c_vkill : char ;  (* Kill line character (usually ctrl-U). *)

       mutable c_veof : char ;	(* End-of-file character (usually ctrl-D). *)

       mutable c_veol : char ;	(* Alternate end-of-line char. (usually none). *)

       mutable c_vmin : int ;  (* Minimum number of characters to read before the read request is
       satisfied. *)

       mutable c_vtime : int ;	(* Maximum read wait (in 0.1s units). *)

       mutable c_vstart : char ;  (* Start character (usually ctrl-Q). *)

       mutable c_vstop : char ;  (* Stop character (usually ctrl-S). *)
	}

       val tcgetattr : file_descr -> terminal_io

       Return the status of the terminal referred to by the given file descriptor.

       type setattr_when =
	| TCSANOW
	| TCSADRAIN
	| TCSAFLUSH

       val tcsetattr : file_descr -> setattr_when -> terminal_io -> unit

       Set the status of the terminal referred to by the given file descriptor. The second  argu-
       ment indicates when the status change takes place: immediately ( TCSANOW ), when all pend-
       ing output has been transmitted ( TCSADRAIN ), or after flushing all input that	has  been
       received  but  not  read ( TCSAFLUSH ).	TCSADRAIN is recommended when changing the output
       parameters; TCSAFLUSH , when changing the input parameters.

       val tcsendbreak : file_descr -> int -> unit

       Send a break condition on the given file descriptor.  The second argument is the  duration
       of the break, in 0.1s units; 0 means standard duration (0.25s).

       val tcdrain : file_descr -> unit

       Waits until all output written on the given file descriptor has been transmitted.

       type flush_queue =
	| TCIFLUSH
	| TCOFLUSH
	| TCIOFLUSH

       val tcflush : file_descr -> flush_queue -> unit

       Discard	data  written  on  the	given  file  descriptor  but not yet transmitted, or data
       received but not yet read,  depending  on  the  second  argument:  TCIFLUSH  flushes  data
       received  but  not  read, TCOFLUSH flushes data written but not transmitted, and TCIOFLUSH
       flushes both.

       type flow_action =
	| TCOOFF
	| TCOON
	| TCIOFF
	| TCION

       val tcflow : file_descr -> flow_action -> unit

       Suspend or restart reception or transmission of data on the given file descriptor, depend-
       ing  on	the second argument: TCOOFF suspends output, TCOON restarts output, TCIOFF trans-
       mits a STOP character to suspend input, and TCION transmits a START character  to  restart
       input.

       val setsid : unit -> int

       Put the calling process in a new session and detach it from its controlling terminal.

OCamldoc				    2014-06-09					  Unix(3)
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