Provided by: ocaml-man_5.2.0-3_all 
NAME
Unix - Interface to the Unix system.
Module
Module Unix
Documentation
Module Unix
: sig end
Interface to the Unix system.
To use the labeled version of this module, add module Unix = UnixLabels in your implementation.
Note: all the functions of this module (except Unix.error_message and Unix.handle_unix_error ) are liable
to raise the Unix.Unix_error exception whenever the underlying system call signals an error.
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.
UnixLabels.Unix_error and Unix.Unix_error are the same, and catching one will catch the other.
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.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''. The returned
array is empty if the process has special privileges.
val unsafe_environment : unit -> string array
Return the process environment, as an array of strings with the format ``variable=value''. Unlike
Unix.environment , this function returns a populated array even if the process has special privileges.
See the documentation for Unix.unsafe_getenv for more details.
Since 4.06 (4.12 in UnixLabels)
val getenv : string -> string
Return the value associated to a variable in the process environment, unless the process has special
privileges.
Raises Not_found if the variable is unbound or the process has special privileges.
This function is identical to Sys.getenv .
val unsafe_getenv : string -> string
Return the value associated to a variable in the process environment.
Unlike Unix.getenv , this function returns the value even if the process has special privileges. It is
considered unsafe because the programmer of a setuid or setgid program must be careful to avoid using
maliciously crafted environment variables in the search path for executables, the locations for temporary
files or logs, and the like.
Since 4.06
Raises Not_found if the variable is unbound.
val putenv : string -> string -> unit
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.
On Windows: only WEXITED is used (as there are no inter-process signals) but with specific return codes
to indicate special termination causes. Look for NTSTATUS values in the Windows documentation to decode
such error return codes. In particular, STATUS_ACCESS_VIOLATION error code is the 32-bit 0xC0000005 : as
Int32.of_int 0xC0000005 is -1073741819 , WEXITED -1073741819 is the Windows equivalent of WSIGNALED
Sys.sigsegv .
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 current process
environment. Note that the first argument, args.(0) , is by convention the filename of the program being
executed, just like Sys.argv.(0) . These execv* functions never return: on success, the current program
is replaced by the new one.
On Windows: the CRT simply spawns a new process and exits the current one. This will have unwanted
consequences if e.g. another process is waiting on the current one. Using Unix.create_process or one of
the open_process_* functions instead is recommended.
Raises Unix_error on failure
val execve : string -> string array -> string array -> 'a
Same as Unix.execv , except that the third argument provides the environment to the program 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. It fails if the OCaml process is multi-core (any domain has been spawned). In addition,
if any thread from the Thread module has been spawned, then the child process might be in a corrupted
state.
Raises Invalid_argument on Windows. Use Unix.create_process or threads instead.
Raises Failure if any domain has been spawned.
val wait : unit -> int * process_status
Wait until one of the children processes die, and return its pid and termination status.
Raises Invalid_argument on Windows. Use Unix.waitpid instead.
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, and whether it should report stopped children.
On Windows: can only wait for a given PID, not any child process.
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 (or the command interpreter cmd.exe on Windows) and therefore can
contain redirections, quotes, variables, etc. To properly quote whitespace and shell special characters
occurring in file names or command arguments, the use of Filename.quote_command is recommended. The
result WEXITED 127 indicates that the shell couldn't be executed.
val _exit : int -> 'a
Terminate the calling process immediately, returning the given status code to the operating system:
usually 0 to indicate no errors, and a small positive integer to indicate failure. Unlike exit ,
Unix._exit performs no finalization whatsoever: functions registered with at_exit are not called,
input/output channels are not flushed, and the C run-time system is not finalized either.
The typical use of Unix._exit is after a Unix.fork operation, when the child process runs into a fatal
error and must exit. In this case, it is preferable to not perform any finalization action in the child
process, as these actions could interfere with similar actions performed by the parent process. For
example, output channels should not be flushed by the child process, as the parent process may flush them
again later, resulting in duplicate output.
Since 4.12
val getpid : unit -> int
Return the pid of the process.
val getppid : unit -> int
Return the pid of the parent process.
Raises Invalid_argument on Windows (because it is meaningless)
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.
Raises Invalid_argument on Windows
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
*)
| O_CLOEXEC (* Set the close-on-exec flag on the descriptor returned by Unix.openfile . See
Unix.set_close_on_exec for more information.
*)
| O_KEEPEXEC (* Clear the close-on-exec flag. This is currently the default.
*)
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 (see Unix.umask ). Return a file descriptor on the named file.
val close : file_descr -> unit
Close a file descriptor.
val fsync : file_descr -> unit
Flush file buffers to disk.
Since 4.08 (4.12 in UnixLabels)
val read : file_descr -> bytes -> int -> int -> int
read fd buf pos len reads len bytes from descriptor fd , storing them in byte sequence buf , starting at
position pos in buf . Return the number of bytes actually read.
val read_bigarray : file_descr -> ('a, Bigarray.int8_unsigned_elt, Bigarray.c_layout) Bigarray.Array1.t
-> int -> int -> int
Same as Unix.read , but read the data into a bigarray.
Since 5.2
val write : file_descr -> bytes -> int -> int -> int
write fd buf pos len writes len bytes to descriptor fd , taking them from byte sequence buf , starting at
position pos in buff . Return the number of bytes actually written. write repeats the writing operation
until all bytes have been written or an error occurs.
val write_bigarray : file_descr -> ('a, Bigarray.int8_unsigned_elt, Bigarray.c_layout) Bigarray.Array1.t
-> int -> int -> int
Same as Unix.write , but take the data from a bigarray.
Since 5.2
val single_write : file_descr -> bytes -> int -> int -> int
Same as Unix.write , but attempts to write only once. Thus, if an error occurs, single_write guarantees
that no data has been written.
val write_substring : file_descr -> string -> int -> int -> int
Same as Unix.write , but take the data from a string instead of a byte sequence.
Since 4.02
val single_write_substring : file_descr -> string -> int -> int -> int
Same as Unix.single_write , but take the data from a string instead of a byte sequence.
Since 4.02
val single_write_bigarray : file_descr -> ('a, Bigarray.int8_unsigned_elt, Bigarray.c_layout)
Bigarray.Array1.t -> int -> int -> int
Same as Unix.single_write , but take the data from a bigarray.
Since 5.2
Interfacing with the standard input/output library
val in_channel_of_descr : file_descr -> 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. Text mode is supported only if the descriptor
refers to a file or pipe, but is not supported if it refers to a socket.
On Windows: set_binary_mode_in always fails on channels created with this function.
Beware that input channels are buffered, so more characters may have been read from the descriptor than
those accessed using channel functions. Channels also keep a copy of the current position in the file.
Closing the channel ic returned by in_channel_of_descr fd using close_in ic also closes the underlying
descriptor fd . It is incorrect to close both the channel ic and the descriptor fd .
If several channels are created on the same descriptor, one of the channels must be closed, but not the
others. Consider for example a descriptor s connected to a socket and two channels ic =
in_channel_of_descr s and oc = out_channel_of_descr s . The recommended closing protocol is to perform
close_out oc , which flushes buffered output to the socket then closes the socket. The ic channel must
not be closed and will be collected by the GC eventually.
val out_channel_of_descr : file_descr -> 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. Text mode is supported only if the descriptor
refers to a file or pipe, but is not supported if it refers to a socket.
On Windows: set_binary_mode_out always fails on channels created with this function.
Beware that output channels are buffered, so you may have to call flush to ensure that all data has been
sent to the descriptor. Channels also keep a copy of the current position in the file.
Closing the channel oc returned by out_channel_of_descr fd using close_out oc also closes the underlying
descriptor fd . It is incorrect to close both the channel ic and the descriptor fd .
See Unix.in_channel_of_descr for a discussion of the closing protocol when several channels are created
on the same descriptor.
val descr_of_in_channel : in_channel -> file_descr
Return the descriptor corresponding to an input channel.
val descr_of_out_channel : 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, and return the resulting offset (from the beginning of
the file).
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 ID (if special file)
*)
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.LargeFile.lseek (for positioning a file descriptor), Unix.LargeFile.truncate and
Unix.LargeFile.ftruncate (for changing the size of a file), and Unix.LargeFile.stat ,
Unix.LargeFile.lstat and Unix.LargeFile.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 .
Mapping files into memory
val map_file : file_descr -> ?pos:int64 -> ('a, 'b) Bigarray.kind -> 'c Bigarray.layout -> bool -> int
array -> ('a, 'b, 'c) Bigarray.Genarray.t
Memory mapping of a file as a Bigarray. map_file fd kind layout shared dims returns a Bigarray of kind
kind , layout layout , and dimensions as specified in dims . The data contained in this Bigarray are the
contents of the file referred to by the file descriptor fd (as opened previously with Unix.openfile , for
example). The optional pos parameter is the byte offset in the file of the data being mapped; it
defaults to 0 (map from the beginning of the file).
If shared is true , all modifications performed on the array are reflected in the file. This requires
that fd be opened with write permissions. If shared is false , modifications performed on the array are
done in memory only, using copy-on-write of the modified pages; the underlying file is not affected.
Unix.map_file is much more efficient than reading the whole file in a Bigarray, modifying that Bigarray,
and writing it afterwards.
To adjust automatically the dimensions of the Bigarray to the actual size of the file, the major
dimension (that is, the first dimension for an array with C layout, and the last dimension for an array
with Fortran layout) can be given as -1 . Unix.map_file then determines the major dimension from the
size of the file. The file must contain an integral number of sub-arrays as determined by the non-major
dimensions, otherwise Failure is raised.
If all dimensions of the Bigarray are given, the file size is matched against the size of the Bigarray.
If the file is larger than the Bigarray, only the initial portion of the file is mapped to the Bigarray.
If the file is smaller than the big array, the file is automatically grown to the size of the Bigarray.
This requires write permissions on fd .
Array accesses are bounds-checked, but the bounds are determined by the initial call to map_file .
Therefore, you should make sure no other process modifies the mapped file while you're accessing it, or a
SIGBUS signal may be raised. This happens, for instance, if the file is shrunk.
Invalid_argument or Failure may be raised in cases where argument validation fails.
Since 4.06
Operations on file names
val unlink : string -> unit
Removes the named file.
If the named file is a directory, raises:
- EPERM on POSIX compliant system
- EISDIR on Linux >= 2.1.132
- EACCESS on Windows
val rename : string -> string -> unit
rename src dst changes the name of a file from src to dst , moving it between directories if needed. If
dst already exists, its contents will be replaced with those of src . Depending on the operating system,
the metadata (permissions, owner, etc) of dst can either be preserved or be replaced by those of src .
val link : ?follow:bool -> string -> string -> unit
link ?follow src dst creates a hard link named dst to the file named src .
Raises ENOSYS On Unix if ~follow:_ is requested, but linkat is unavailable.
Raises ENOSYS On Windows if ~follow:false is requested.
val realpath : string -> string
realpath p is an absolute pathname for p obtained by resolving all extra / characters, relative path
segments and symbolic links.
Since 4.13
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.
Raises Invalid_argument on Windows
val chown : string -> int -> int -> unit
Change the owner uid and owner gid of the named file.
Raises Invalid_argument on Windows
val fchown : file_descr -> int -> int -> unit
Change the owner uid and owner gid of an opened file.
Raises Invalid_argument on Windows
val umask : file_perm -> file_perm
Set the process's file mode creation mask, and return the previous mask.
Raises Invalid_argument on Windows
val access : string -> access_permission list -> unit
Check that the process has the given permissions over the named file.
On Windows: execute permission X_OK cannot be tested, just tests for read permission instead.
Raises Unix_error otherwise.
Operations on file descriptors
val dup : ?cloexec:bool -> file_descr -> file_descr
Return a new file descriptor referencing the same file as the given descriptor. See
Unix.set_close_on_exec for documentation on the cloexec optional argument.
val dup2 : ?cloexec:bool -> file_descr -> file_descr -> unit
dup2 src dst duplicates src to dst , closing dst if already opened. See Unix.set_close_on_exec for
documentation on the cloexec optional argument.
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 temporarily 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 ,
create_process and open_process functions.
It is often a security hole to leak file descriptors opened on, say, a private file to an external
program: the program, then, gets access to the private file and can do bad things with it. Hence, it is
highly recommended to set all file descriptors ``close-on-exec'', except in the very few cases where a
file descriptor actually needs to be transmitted to another program.
The best way to set a file descriptor ``close-on-exec'' is to create it in this state. To this end, the
openfile function has O_CLOEXEC and O_KEEPEXEC flags to enforce ``close-on-exec'' mode or
``keep-on-exec'' mode, respectively. All other operations in the Unix module that create file
descriptors have an optional argument ?cloexec:bool to indicate whether the file descriptor should be
created in ``close-on-exec'' mode (by writing ~cloexec:true ) or in ``keep-on-exec'' mode (by writing
~cloexec:false ). For historical reasons, the default file descriptor creation mode is ``keep-on-exec'',
if no cloexec optional argument is given. This is not a safe default, hence it is highly recommended to
pass explicit cloexec arguments to operations that create file descriptors.
The cloexec optional arguments and the O_KEEPEXEC flag were introduced in OCaml 4.05. Earlier, the
common practice was to create file descriptors in the default, ``keep-on-exec'' mode, then call
set_close_on_exec on those freshly-created file descriptors. This is not as safe as creating the file
descriptor in ``close-on-exec'' mode because, in multithreaded programs, a window of vulnerability exists
between the time when the file descriptor is created and the time set_close_on_exec completes. If
another thread spawns another program during this window, the descriptor will leak, as it is still in the
``keep-on-exec'' mode.
Regarding the atomicity guarantees given by ~cloexec:true or by the use of the O_CLOEXEC flag: on all
platforms it is guaranteed that a concurrently-executing Caml thread cannot leak the descriptor by
starting a new process. On Linux, this guarantee extends to concurrently-executing C threads. As of Feb
2017, other operating systems lack the necessary system calls and still expose a window of vulnerability
during which a C thread can see the newly-created file descriptor in ``keep-on-exec'' mode.
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 (see Unix.umask ).
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.
Raises Invalid_argument on Windows
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 : ?cloexec:bool -> 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. See Unix.set_close_on_exec for
documentation on the cloexec optional argument.
val mkfifo : string -> file_perm -> unit
Create a named pipe with the given permissions (see Unix.umask ).
Raises Invalid_argument on Windows
High-level process and redirection management
val create_process : string -> string array -> file_descr -> file_descr -> file_descr -> int
create_process prog args stdin stdout stderr creates a new process that executes the program in file prog
, with arguments args . Note that the first argument, args.(0) , is by convention the filename of the
program being executed, just like Sys.argv.(0) . 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 stdin , stdout and stderr . Passing e.g. Unix.stdout for
stdout prevents the redirection and causes the new process to have the same standard output as the
current process. The executable 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 stdin stdout stderr works as Unix.create_process , except that the extra
argument env specifies the environment passed to the program.
val open_process_in : string -> 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 (or cmd.exe on Windows), cf. Unix.system
. The Filename.quote_command function can be used to quote the command and its arguments as appropriate
for the shell being used. If the command does not need to be run through the shell,
Unix.open_process_args_in can be used as a more robust and more efficient alternative to
Unix.open_process_in .
val open_process_out : string -> 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 flush at the right times to ensure correct
synchronization. If the command does not need to be run through the shell, Unix.open_process_args_out
can be used instead of Unix.open_process_out .
val open_process : string -> in_channel * 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 connected to the output of the
command, and the output channel to the input of the command. If the command does not need to be run
through the shell, Unix.open_process_args can be used instead of Unix.open_process .
val open_process_full : string -> string array -> in_channel * out_channel * 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. If the command does not need to be run through the shell,
Unix.open_process_args_full can be used instead of Unix.open_process_full .
val open_process_args : string -> string array -> in_channel * out_channel
open_process_args prog args runs the program prog with arguments args . Note that the first argument,
args.(0) , is by convention the filename of the program being executed, just like Sys.argv.(0) . The new
process executes concurrently with the current process. The standard input and output of the new process
are redirected to pipes, which can be respectively read and written via the returned channels. The input
channel is connected to the output of the program, and the output channel to the input of the program.
Warning: writes on output channels are buffered, hence be careful to call flush at the right times to
ensure correct synchronization.
The executable file prog is searched for in the path. This behaviour changed in 4.12; previously prog was
looked up only in the current directory.
The new process has the same environment as the current process.
Since 4.08
val open_process_args_in : string -> string array -> in_channel
Same as Unix.open_process_args , but redirects only the standard output of the new process.
Since 4.08
val open_process_args_out : string -> string array -> out_channel
Same as Unix.open_process_args , but redirects only the standard input of the new process.
Since 4.08
val open_process_args_full : string -> string array -> string array -> in_channel * out_channel *
in_channel
Similar to Unix.open_process_args , but the third argument specifies the environment passed to the new
process. The result is a triple of channels connected respectively to the standard output, standard
input, and standard error of the program.
Since 4.08
val process_in_pid : in_channel -> int
Return the pid of a process opened via Unix.open_process_args_in or the pid of the shell opened via
Unix.open_process_in .
Since 4.08 (4.12 in UnixLabels)
val process_out_pid : out_channel -> int
Return the pid of a process opened via Unix.open_process_args_out or the pid of the shell opened via
Unix.open_process_out .
Since 4.08 (4.12 in UnixLabels)
val process_pid : in_channel * out_channel -> int
Return the pid of a process opened via Unix.open_process_args or the pid of the shell opened via
Unix.open_process_args .
Since 4.08 (4.12 in UnixLabels)
val process_full_pid : in_channel * out_channel * in_channel -> int
Return the pid of a process opened via Unix.open_process_args_full or the pid of the shell opened via
Unix.open_process_full .
Since 4.08 (4.12 in UnixLabels)
val close_process_in : in_channel -> process_status
Close channels opened by Unix.open_process_in , wait for the associated command to terminate, and return
its termination status.
val close_process_out : out_channel -> process_status
Close channels opened by Unix.open_process_out , wait for the associated command to terminate, and return
its termination status.
val close_process : in_channel * 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 : in_channel * out_channel * in_channel -> process_status
Close channels opened by Unix.open_process_full , wait for the associated command to terminate, and
return its termination status.
Symbolic links
val symlink : ?to_dir:bool -> string -> string -> unit
symlink ?to_dir src dst creates the file dst as a symbolic link to the file src . On Windows, ~to_dir
indicates if the symbolic link points to a directory or a file; if omitted, symlink examines src using
stat and picks appropriately, if src does not exist then false is assumed (for this reason, it is
recommended that the ~to_dir parameter be specified in new code). On Unix, ~to_dir is ignored.
Windows symbolic links are available in Windows Vista onwards. There are some important differences
between Windows symlinks and their POSIX counterparts.
Windows symbolic links come in two flavours: directory and regular, which designate whether the symbolic
link points to a directory or a file. The type must be correct - a directory symlink which actually
points to a file cannot be selected with chdir and a file symlink which actually points to a directory
cannot be read or written (note that Cygwin's emulation layer ignores this distinction).
When symbolic links are created to existing targets, this distinction doesn't matter and symlink will
automatically create the correct kind of symbolic link. The distinction matters when a symbolic link is
created to a non-existent target.
The other caveat is that by default symbolic links are a privileged operation. Administrators will always
need to be running elevated (or with UAC disabled) and by default normal user accounts need to be granted
the SeCreateSymbolicLinkPrivilege via Local Security Policy (secpol.msc) or via Active Directory.
Unix.has_symlink can be used to check that a process is able to create symbolic links.
val has_symlink : unit -> bool
Returns true if the user is able to create symbolic links. On Windows, this indicates that the user not
only has the SeCreateSymbolicLinkPrivilege but is also running elevated, if necessary. On other
platforms, this is simply indicates that the symlink system call is available.
Since 4.03
val readlink : string -> string
Read the contents of a symbolic 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 exceptional 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 mode len 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 len bytes forward if len is positive, len
bytes backwards if len is negative, or to the end of the file if len 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.
What happens when a process tries to lock a region of a file that is already locked by the same process
depends on the OS. On POSIX-compliant systems, the second lock operation succeeds and may "promote" the
older lock from read lock to write lock. On Windows, the second lock operation will block or fail.
Signals
Note: installation of signal handlers is performed via the functions Sys.signal and Sys.set_signal .
val kill : int -> int -> unit
kill pid signal sends signal number signal to the process with id pid .
On Windows: only the Sys.sigkill signal is emulated.
type sigprocmask_command =
| SIG_SETMASK
| SIG_BLOCK
| SIG_UNBLOCK
val sigprocmask : sigprocmask_command -> int list -> int list
sigprocmask mode sigs changes the set of blocked signals. If mode is SIG_SETMASK , blocked signals are
set to those in the list sigs . If mode is SIG_BLOCK , the signals in sigs are added to the set of
blocked signals. If mode is SIG_UNBLOCK , the signals in sigs are removed from the set of blocked
signals. sigprocmask returns the set of previously blocked signals.
When the systhreads version of the Thread module is loaded, this function redirects to Thread.sigmask .
I.e., sigprocmask only changes the mask of the current thread.
Raises Invalid_argument on Windows (no inter-process signals on Windows)
val sigpending : unit -> int list
Return the set of blocked signals that are currently pending.
Raises Invalid_argument on Windows (no inter-process signals on Windows)
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.
Raises Invalid_argument on Windows (no inter-process signals on Windows)
val pause : unit -> unit
Wait until a non-ignored, non-blocked signal is delivered.
Raises Invalid_argument on Windows (no inter-process signals on Windows)
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. To perform the inverse conversion, set the TZ environment variable
to "UTC", use Unix.mktime , and then restore the original value of TZ.
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. The function performing the inverse conversion is Unix.mktime .
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 October 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.
Raises Invalid_argument on Windows
val sleep : int -> unit
Stop execution for the given number of seconds.
val sleepf : float -> unit
Stop execution for the given number of seconds. Like sleep , but fractions of seconds are supported.
Since 4.03 (4.12 in UnixLabels)
val times : unit -> process_times
Return the execution times of the process.
On Windows: partially implemented, will not report timings for child processes.
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. If both times are 0.0 , the access and last
modification times are both set to 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.
Raises Invalid_argument on Windows
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
disables the timer. Setting s.it_interval to zero causes the timer to be disabled after its next
expiration.
Raises Invalid_argument on Windows
User id, group id
val getuid : unit -> int
Return the user id of the user executing the process.
On Windows: always returns 1 .
val geteuid : unit -> int
Return the effective user id under which the process runs.
On Windows: always returns 1 .
val setuid : int -> unit
Set the real user id and effective user id for the process.
Raises Invalid_argument on Windows
val getgid : unit -> int
Return the group id of the user executing the process.
On Windows: always returns 1 .
val getegid : unit -> int
Return the effective group id under which the process runs.
On Windows: always returns 1 .
val setgid : int -> unit
Set the real group id and effective group id for the process.
Raises Invalid_argument on Windows
val getgroups : unit -> int array
Return the list of groups to which the user executing the process belongs.
On Windows: always returns [|1|] .
val setgroups : int array -> unit
setgroups groups sets the supplementary group IDs for the calling process. Appropriate privileges are
required.
Raises Invalid_argument on Windows
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.
Raises Invalid_argument on Windows
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.
Raises Not_found if no such entry exists, or always on Windows.
val getgrnam : string -> group_entry
Find an entry in group with the given name.
Raises Not_found if no such entry exists, or always on Windows.
val getpwuid : int -> passwd_entry
Find an entry in passwd with the given user id.
Raises Not_found if no such entry exists, or always on Windows.
val getgrgid : int -> group_entry
Find an entry in group with the given group id.
Raises Not_found if no such entry exists, or always on Windows.
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 representation. 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.
Raises 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 ).
val is_inet6_addr : inet_addr -> bool
Whether the given inet_addr is an IPv6 address.
Since 4.12
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 ).
On Windows: PF_UNIX supported since 4.14.0 on Windows 10 1803 and later.
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. SOCK_SEQPACKET is included for
completeness, but is rarely supported by the OS, and needs system calls that are not available in this
library.
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 : ?cloexec:bool -> 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. See Unix.set_close_on_exec for
documentation on the cloexec optional argument.
val domain_of_sockaddr : sockaddr -> socket_domain
Return the socket domain adequate for the given socket address.
val socketpair : ?cloexec:bool -> socket_domain -> socket_type -> int -> file_descr * file_descr
Create a pair of unnamed sockets, connected together. See Unix.set_close_on_exec for documentation on
the cloexec optional argument.
val accept : ?cloexec:bool -> 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. See Unix.set_close_on_exec for documentation
on the cloexec optional argument.
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 -> bytes -> int -> int -> msg_flag list -> int
Receive data from a connected socket.
val recvfrom : file_descr -> bytes -> int -> int -> msg_flag list -> int * sockaddr
Receive data from an unconnected socket.
val send : file_descr -> bytes -> int -> int -> msg_flag list -> int
Send data over a connected socket.
val send_substring : file_descr -> string -> int -> int -> msg_flag list -> int
Same as send , but take the data from a string instead of a byte sequence.
Since 4.02
val sendto : file_descr -> bytes -> int -> int -> msg_flag list -> sockaddr -> int
Send data over an unconnected socket.
val sendto_substring : file_descr -> string -> int -> int -> msg_flag list -> sockaddr -> int
Same as sendto , but take the data from a string instead of a byte sequence.
Since 4.02
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
*)
| SO_REUSEPORT (* Allow reuse of address and port bindings.
Since 4.12.
*)
The socket options that can be consulted with Unix.getsockopt and modified with Unix.setsockopt . 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 (* .B "Deprecated." Use Unix.getsockopt_error instead.
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 meaning ``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 -> in_channel * out_channel
Connect to a server at the given address. Return a pair of buffered channels connected to the server.
Remember to call flush on the output channel at the right times to ensure correct synchronization.
The two channels returned by open_connection share a descriptor to a socket. Therefore, when the
connection is over, you should call close_out on the output channel, which will also close the underlying
socket. Do not call close_in on the input channel; it will be collected by the GC eventually.
val shutdown_connection : 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. This does not close the socket and
the channels used by the connection. See Unix.open_connection for how to close them once the connection
is over.
val establish_server : (in_channel -> out_channel -> unit) -> sockaddr -> 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.
The two channels given to the function share a descriptor to a socket. The function does not need to
close the channels, since this occurs automatically when the function returns. If the function prefers
explicit closing, it should close the output channel using close_out and leave the input channel
unclosed, for reasons explained in Unix.in_channel_of_descr .
Raises Invalid_argument on Windows. Use threads instead.
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.
Raises Not_found if no such entry exists.
val gethostbyaddr : inet_addr -> host_entry
Find an entry in hosts with the given address.
Raises Not_found if no such entry exists.
val getprotobyname : string -> protocol_entry
Find an entry in protocols with the given name.
Raises Not_found if no such entry exists.
val getprotobynumber : int -> protocol_entry
Find an entry in protocols with the given protocol number.
Raises Not_found if no such entry exists.
val getservbyname : string -> string -> service_entry
Find an entry in services with the given name.
Raises Not_found if no such entry exists.
val getservbyport : int -> string -> service_entry
Find an entry in services with the given service number.
Raises Not_found if no such entry exists.
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.
Raises 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.
Raises Invalid_argument on Windows
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 argument indicates
when the status change takes place: immediately ( TCSANOW ), when all pending 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.
Raises Invalid_argument on Windows
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).
Raises Invalid_argument on Windows
val tcdrain : file_descr -> unit
Waits until all output written on the given file descriptor has been transmitted.
Raises Invalid_argument on Windows
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.
Raises Invalid_argument on Windows
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, depending on the
second argument: TCOOFF suspends output, TCOON restarts output, TCIOFF transmits a STOP character to
suspend input, and TCION transmits a START character to restart input.
Raises Invalid_argument on Windows
val setsid : unit -> int
Put the calling process in a new session and detach it from its controlling terminal.
Raises Invalid_argument on Windows