Up

module Lwt_unix

: sig

Cooperative system calls

This modules maps system calls, like those of the standard library's Unix module, to cooperative ones, which will not block the program.

The semantics of all operations is the following: if the action (for example reading from a file descriptor) can be performed immediately, it is done and returns immediately, otherwise it returns a sleeping thread which is woken up when the operation completes.

Most operations on sockets and pipes (on Windows it is only sockets) are cancelable, meaning you can cancel them with Lwt.cancel. For example if you want to read something from a file descriptor with a timeout, you can cancel the action after the timeout and the reading will not be performed if not already done.

For example, consider that you have two sockets sock1 and sock2. You want to read something from sock1 or exclusively from sock2 and fail with an exception if a timeout of 1 second expires, without reading anything from sock1 and sock2, even if they become readable in the future.

Then you can do:

    Lwt.pick [Lwt_unix.timeout 1.0; read sock1 buf1 ofs1 len1; read sock2 buf2 ofs2 len2]

In this case, it is guaranteed that exactly one of the three operations will complete, and the others will be cancelled.

#
val handle_unix_error : ('a -> 'b Lwt.t) -> 'a -> 'b Lwt.t

Same as Unix.handle_unix_error but catches lwt-level exceptions

Configuration

#
type async_method =
# | Async_none
(*System calls are made synchronously, and may block the entire program.*)
# | Async_detach
(*System calls are made in another system thread, thus without blocking other Lwt threads. The drawback is that it may degrade performances in some cases.
This is the default.		*)
# | Async_switch
(*System calls are made in the main thread, and if one blocks the execution continue in another system thread. This method is the most efficient, also you will get better performance if you force all threads to run on the same cpu. On linux this can be done by using the command taskset.
Note that this method is still experimental.		*)

For system calls that cannot be made asynchronously, Lwt uses one of the following method:

#
val default_async_method : unit -> async_method

Returns the default async method.

This can be initialized using the environment variable "LWT_ASYNC_METHOD" with possible values "none", "detach" and "switch".

#
val set_default_async_method : async_method -> unit

Sets the default async method.

#
val async_method : unit -> async_method

async_method () returns the async method used in the current thread.

#
val async_method_key : async_method Lwt.key

The key for storing the local async method.

#
val with_async_none : (unit -> 'a) -> 'a

with_async_none f is a shorthand for:

        Lwt.with_value async_method_key (Some Async_none) f
#
val with_async_detach : (unit -> 'a) -> 'a

with_async_none f is a shorthand for:

        Lwt.with_value async_method_key (Some Async_detach) f
#
val with_async_switch : (unit -> 'a) -> 'a

with_async_none f is a shorthand for:

        Lwt.with_value async_method_key (Some Async_switch) f

Sleeping

#
val sleep : float -> unit Lwt.t

sleep d is a thread that remains suspended for d seconds and then terminates.

#
val yield : unit -> unit Lwt.t

yield () is a thread that suspends itself and then resumes as soon as possible and terminates.

#
val auto_yield : float -> unit -> unit Lwt.t

auto_yield timeout returns a function f that will yield every timeout seconds.

#
exception Timeout

Exception raised by timeout operations

#
val timeout : float -> 'a Lwt.t

timeout d is a thread that remains suspended for d seconds and then fails with Timeout.

#
val with_timeout : float -> (unit -> 'a Lwt.t) -> 'a Lwt.t

with_timeout d f is a short-hand for:

        Lwt.pick [Lwt_unix.timeout d; f ()]

Operation on file-descriptors

#
type file_descr

The abstract type for file descriptors. A Lwt file descriptor is a pair of a unix file descriptor (of type Unix.file_descr) and a state.

A file descriptor may be:

  • opened, in which case it is fully usable
  • closed or aborted, in which case it is no longer usable
#
type state =
# | Opened
(*The file descriptor is opened*)
# | Closed
(*The file descriptor has been closed by close. It must not be used for any operation.*)
# | Aborted of exn
(*The file descriptor has been aborted, the only operation possible is close, all others will fail.*)

State of a file descriptor

#
val state : file_descr -> state

state fd returns the state of fd

#
val unix_file_descr : file_descr -> Unix.file_descr

Returns the underlying unix file descriptor. It always succeeds, even if the file descriptor's state is not [root:Open].

#
val of_unix_file_descr : ?blocking:bool -> ?set_flags:bool -> Unix.file_descr -> file_descr

Creates a lwt file descriptor from a unix one.

blocking is the blocking mode of the file-descriptor, and describes how Lwt will use it. In non-blocking mode, read/write on this file descriptor are made using non-blocking IO; in blocking mode they are made using the current async method. If blocking is not specified it is guessed according to the file kind: socket and pipes are in non-blocking mode and others are in blocking mode.

If set_flags is true (the default) then the file flags are modified according to the blocking argument, otherwise they are left unchanged.

Note that the blocking mode is less efficient than the non-blocking one, so it should be used only for file descriptors that does not support asynchronous operations, such as regular files, or for shared descriptors such as stdout, stderr or stdin.

#
val blocking : file_descr -> bool Lwt.t

blocking fd returns whether fd is used in blocking or non-blocking mode.

#
val set_blocking : ?set_flags:bool -> file_descr -> bool -> unit

set_blocking fd b puts fd in blocking or non-blocking mode. If set_flags is true (the default) then the file flags are modified, otherwise the modification is only done at the application level.

#
val abort : file_descr -> exn -> unit

abort fd exn makes all current and further uses of the file descriptor fail with the given exception. This put the file descriptor into the Aborted state.

If the file descriptor is closed, this does nothing, if it is aborted, this replace the abort exception by exn.

Note that this only works for reading and writing operations on file descriptors supporting non-blocking mode.

Process handling

#
val fork : unit -> int

fork () does the same as Unix.fork. You must use this function instead of Unix.fork when you want to use Lwt in the child process.

Notes:

  • in the child process all pending jobs are canceled,
  • if you are going to use Lwt in the parent and the child, it is a good idea to call Lwt_io.flush_all before callling fork to avoid double-flush.
#
type process_status = Unix.process_status =
# | WEXITED of int
# | WSIGNALED of int
# | WSTOPPED of int
#
type wait_flag = Unix.wait_flag =
# | WNOHANG
# | WUNTRACED
#
val wait : unit -> (int * process_status) Lwt.t

Wrapper for Unix.wait

#
val waitpid : wait_flag list -> int -> (int * process_status) Lwt.t

Wrapper for Unix.waitpid

#
type resource_usage = {
# ru_utime
: float;(*User time used*)
# ru_stime
: float;(*System time used*)
}

Resource usages

#
val wait4 : wait_flag list -> int -> (int * process_status * resource_usage) Lwt.t

wait4 flags pid returns (pid, status, rusage) where (pid, status) is the same result as Unix.waitpid flags pid, and rusage contains accounting information about the child.

On windows it will always returns { utime = 0.0; stime = 0.0 }.

#
val wait_count : unit -> int

Returns the number of threads waiting for a child to terminate.

#
val system : string -> process_status Lwt.t

Executes the given command, waits until it terminates, and return its termination status. The string is interpreted by the shell /bin/sh on Unix and cmd.exe on Windows. The result WEXITED 127 indicates that the shell couldn't be executed.

Basic file input/output

#
val stdin : file_descr

The standard file descriptor for input. This one is usually a terminal is the program is started from a terminal.

#
val stdout : file_descr

The standard file descriptor for output

#
val stderr : file_descr

The standard file descriptor for printing error messages

#
type file_perm = Unix.file_perm
#
type open_flag = Unix.open_flag =
# | O_RDONLY
# | O_WRONLY
# | O_RDWR
# | O_NONBLOCK
# | O_APPEND
# | O_CREAT
# | O_TRUNC
# | O_EXCL
# | O_NOCTTY
# | O_DSYNC
# | O_SYNC
# | O_RSYNC
# | O_SHARE_DELETE
# | O_CLOEXEC
#
val openfile : string -> open_flag list -> file_perm -> file_descr Lwt.t

Wrapper for Unix.openfile.

#
val close : file_descr -> unit Lwt.t

Close a file descriptor. This close the underlying unix file descriptor and set its state to Closed

#
val read : file_descr -> string -> int -> int -> int Lwt.t

read fd buf ofs len has the same semantic as Unix.read, but is cooperative

#
val write : file_descr -> string -> int -> int -> int Lwt.t

read fd buf ofs len has the same semantic as Unix.write, but is cooperative

#
val readable : file_descr -> bool

Returns whether the given file descriptor is currently readable.

#
val writable : file_descr -> bool

Returns whether the given file descriptor is currently writable.

#
val wait_read : file_descr -> unit Lwt.t

waits (without blocking other threads) until there is something to read on the file descriptor

#
val wait_write : file_descr -> unit Lwt.t

waits (without blocking other threads) until it is possible to write on the file descriptor

Seeking and truncating

#
type seek_command = Unix.seek_command =
# | SEEK_SET
# | SEEK_CUR
# | SEEK_END
#
val lseek : file_descr -> int -> seek_command -> int Lwt.t

Wrapper for Unix.lseek

#
val truncate : string -> int -> unit Lwt.t

Wrapper for Unix.truncate

#
val ftruncate : file_descr -> int -> unit Lwt.t

Wrapper for Unix.ftruncate

Syncing

#
val fsync : file_descr -> unit Lwt.t

Synchronise all data and metadata of the file descriptor with the disk. On Windows it uses FlushFileBuffers.

#
val fdatasync : file_descr -> unit Lwt.t

Synchronise all data (but not metadata) of the file descriptor with the disk.

Note that fdatasync is not available on all platforms.

File status

#
type file_kind = Unix.file_kind =
# | S_REG
# | S_DIR
# | S_CHR
# | S_BLK
# | S_LNK
# | S_FIFO
# | S_SOCK
#
type stats = Unix.stats = {
# st_dev
: int;
# st_ino
: int;
# st_kind
: file_kind;
# st_perm
: file_perm;
: int;
# st_uid
: int;
# st_gid
: int;
# st_rdev
: int;
# st_size
: int;
# st_atime
: float;
# st_mtime
: float;
# st_ctime
: float;
}
#
val stat : string -> stats Lwt.t

Wrapper for Unix.stat

#
val lstat : string -> stats Lwt.t

Wrapper for Unix.lstat

#
val fstat : file_descr -> stats Lwt.t

Wrapper for Unix.fstat

#
val isatty : file_descr -> bool Lwt.t

Wrapper for Unix.isatty

File operations on large files

#
module LargeFile : sig
#
val lseek : file_descr -> int64 -> seek_command -> int64 Lwt.t

Wrapper for Unix.LargeFile.lseek

#
val truncate : string -> int64 -> unit Lwt.t

Wrapper for Unix.LargeFile.truncate

#
val ftruncate : file_descr -> int64 -> unit Lwt.t

Wrapper for Unix.LargeFile.ftruncate

#
type stats = Unix.LargeFile.stats = {
# st_dev
: int;
# st_ino
: int;
# st_kind
: file_kind;
# st_perm
: file_perm;
: int;
# st_uid
: int;
# st_gid
: int;
# st_rdev
: int;
# st_size
: int64;
# st_atime
: float;
# st_mtime
: float;
# st_ctime
: float;
}
#
val stat : string -> stats Lwt.t

Wrapper for Unix.LargeFile.stat

#
val lstat : string -> stats Lwt.t

Wrapper for Unix.LargeFile.lstat

#
val fstat : file_descr -> stats Lwt.t

Wrapper for Unix.LargeFile.fstat

end

Operations on file names

#
val rename : string -> string -> unit Lwt.t

Wrapper for Unix.rename

File permissions and ownership

#
val chmod : string -> file_perm -> unit Lwt.t

Wrapper for Unix.chmod

#
val fchmod : file_descr -> file_perm -> unit Lwt.t

Wrapper for Unix.fchmod

#
val chown : string -> int -> int -> unit Lwt.t

Wrapper for Unix.chown

#
val fchown : file_descr -> int -> int -> unit Lwt.t

Wrapper for Unix.fchown

#
type access_permission = Unix.access_permission =
# | R_OK
# | W_OK
# | X_OK
# | F_OK
#
val access : string -> access_permission list -> unit Lwt.t

Wrapper for Unix.access

Operations on file descriptors

#
val dup : file_descr -> file_descr

Wrapper for Unix.dup

#
val dup2 : file_descr -> file_descr -> unit

Wrapper for Unix.dup2

#
val set_close_on_exec : file_descr -> unit

Wrapper for Unix.set_close_on_exec

#
val clear_close_on_exec : file_descr -> unit

Wrapper for Unix.clear_close_on_exec

Directories

#
val mkdir : string -> file_perm -> unit Lwt.t

Wrapper for Unix.mkdir

#
val rmdir : string -> unit Lwt.t

Wrapper for Unix.rmdir

#
val chdir : string -> unit Lwt.t

Wrapper for Unix.chdir

#
val chroot : string -> unit Lwt.t

Wrapper for Unix.chroot

#
type dir_handle = Unix.dir_handle
#
val opendir : string -> dir_handle Lwt.t

Wrapper for Unix.opendir

#
val readdir : dir_handle -> string Lwt.t

Wrapper for Unix.readdir.

#
val readdir_n : dir_handle -> int -> string array Lwt.t

readdir_n handle count reads at most count entry from the given directory. It is more efficient than calling readdir count times. If the length of the returned array is smaller than count, this means that the end of the directory has been reached.

#
val rewinddir : dir_handle -> unit Lwt.t

Wrapper for Unix.rewinddir

#
val closedir : dir_handle -> unit Lwt.t

Wrapper for Unix.closedir

#
val files_of_directory : string -> string Lwt_stream.t

files_of_directory dir returns the stream of all files of dir.

Pipes and redirections

#
val pipe : unit -> file_descr * file_descr

pipe () creates pipe using Unix.pipe and returns two lwt file descriptors created from unix file_descriptor

#
val pipe_in : unit -> file_descr * Unix.file_descr

pipe_in () is the same as pipe but maps only the unix file descriptor for reading into a lwt one. The second is not put into non-blocking mode. You usually want to use this before forking to receive data from the child process.

#
val pipe_out : unit -> Unix.file_descr * file_descr

pipe_out () is the inverse of pipe_in. You usually want to use this before forking to send data to the child process

#
val mkfifo : string -> file_perm -> unit Lwt.t

Wrapper for Unix.mkfifo

Symbolic links

Locking

#
type lock_command = Unix.lock_command =
# | F_ULOCK
# | F_LOCK
# | F_TLOCK
# | F_TEST
# | F_RLOCK
# | F_TRLOCK
#
val lockf : file_descr -> lock_command -> int -> unit Lwt.t

Wrapper for Unix.lockf

User id, group id

#
type passwd_entry = Unix.passwd_entry = {
# pw_name
: string;
# pw_passwd
: string;
# pw_uid
: int;
# pw_gid
: int;
# pw_gecos
: string;
# pw_dir
: string;
# pw_shell
: string;
}
#
type group_entry = Unix.group_entry = {
# gr_name
: string;
# gr_passwd
: string;
# gr_gid
: int;
# gr_mem
: string array;
}
#
val getlogin : unit -> string Lwt.t

Wrapper for Unix.getlogin

#
val getpwnam : string -> passwd_entry Lwt.t

Wrapper for Unix.getpwnam

#
val getgrnam : string -> group_entry Lwt.t

Wrapper for Unix.getgrnam

#
val getpwuid : int -> passwd_entry Lwt.t

Wrapper for Unix.getpwuid

#
val getgrgid : int -> group_entry Lwt.t

Wrapper for Unix.getgrgid

Signals

#
type signal_handler_id

Id of a signal handler, used to cancel it

#
val on_signal : int -> (int -> unit) -> signal_handler_id

on_signal signum f calls f each time the signal with numnber signum is received by the process. It returns a signal handler identifier that can be used to stop monitoring signum.

#
val on_signal_full : int -> (signal_handler_id -> int -> unit) -> signal_handler_id

on_signal_full f is the same as on_signal f except that f also receive the signal handler identifier as argument so it can disable it.

#
val disable_signal_handler : signal_handler_id -> unit

Stops receiving this signal

#
val signal_count : unit -> int

Returns the number of registered signal handler.

#
val reinstall_signal_handler : int -> unit

reinstall_signal_handler signum if any signal handler is registered for this signal with on_signal, it reinstall the signal handler (with Sys.set_signal). This is usefull in case another part of the program install another signal handler.

Sockets

#
type inet_addr = Unix.inet_addr
#
type socket_domain = Unix.socket_domain =
# | PF_UNIX
# | PF_INET
# | PF_INET6
#
type socket_type = Unix.socket_type =
# | SOCK_STREAM
# | SOCK_DGRAM
# | SOCK_RAW
# | SOCK_SEQPACKET
#
type sockaddr = Unix.sockaddr =
# | ADDR_UNIX of string
# | ADDR_INET of inet_addr * int
#
val socket : socket_domain -> socket_type -> int -> file_descr

socket domain type proto is the same as Unix.socket but maps the result into a lwt file descriptor

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

Wrapper for Unix.socketpair

#
val bind : file_descr -> sockaddr -> unit

Wrapper for Unix.bind

#
val listen : file_descr -> int -> unit

Wrapper for Unix.listen

#
val accept : file_descr -> (file_descr * sockaddr) Lwt.t

Wrapper for Unix.accept

#
val accept_n : file_descr -> int -> ((file_descr * sockaddr) list * exn option) Lwt.t

accept_n fd count accepts up to count connections at one time.

  • if no connection is available right now, it returns a sleeping thread
  • if more than 1 and less than count are available, it returns all of them
  • if more than count are available, it returns the next count of them
  • if an error happens, it returns the connections that have been successfully accepted so far and the error

accept_n has the advantage of improving performance. If you want a more detailed description, you can have a look at:

Acceptable strategies for improving web server performance

#
val connect : file_descr -> sockaddr -> unit Lwt.t

Wrapper for Unix.connect

#
type shutdown_command = Unix.shutdown_command =
# | SHUTDOWN_RECEIVE
# | SHUTDOWN_SEND
# | SHUTDOWN_ALL
#
val shutdown : file_descr -> shutdown_command -> unit

Wrapper for Unix.shutdown

#
val getsockname : file_descr -> sockaddr

Wrapper for Unix.getsockname

#
val getpeername : file_descr -> sockaddr

Wrapper for Unix.getpeername

#
type msg_flag = Unix.msg_flag =
# | MSG_OOB
# | MSG_DONTROUTE
# | MSG_PEEK
#
val recv : file_descr -> string -> int -> int -> msg_flag list -> int Lwt.t

Wrapper for Unix.recv

#
val recvfrom : file_descr -> string -> int -> int -> msg_flag list -> (int * sockaddr) Lwt.t

Wrapper for Unix.recvfrom

#
val send : file_descr -> string -> int -> int -> msg_flag list -> int Lwt.t

Wrapper for Unix.send

#
val sendto : file_descr -> string -> int -> int -> msg_flag list -> sockaddr -> int Lwt.t

Wrapper for Unix.sendto

#
type io_vector = {
# iov_buffer
: string;
# iov_offset
: int;
# iov_length
: int;
}

An io-vector. Used by recv_msg and send_msg.

#
val io_vector : buffer:string -> offset:int -> length:int -> io_vector

Creates an io-vector

#
val recv_msg : socket:file_descr -> io_vectors:io_vector list -> (int * Unix.file_descr list) Lwt.t

recv_msg ~socket ~io_vectors receives data into a list of io-vectors, plus any file-descriptors that may accompany the messages. It returns a tuple whose first field is the number of bytes received and second is a list of received file descriptors. The messages themselves will be recorded in the provided io_vectors list.

This call is not available on windows.

#
val send_msg : socket:file_descr -> io_vectors:io_vector list -> fds:Unix.file_descr list -> int Lwt.t

send_msg ~socket ~io_vectors ~fds sends data from a list of io-vectors, accompanied with a list of file-descriptors. It returns the number of bytes sent. If fd-passing is not possible on the current system and fds is not empty, it raises Lwt_sys.Not_available "fd_passing".

This call is not available on windows.

#
type credentials = {
# cred_pid
: int;
# cred_uid
: int;
# cred_gid
: int;
}
#
val get_credentials : file_descr -> credentials

get_credentials fd returns credential informations from the given socket. On some platforms, obtaining the peer pid is not possible and it will be set to -1. If obtaining credentials is not possible on the current system, it raises Lwt_sys.Not_available "get_credentials".

This call is not available on windows.

Socket options

#
type socket_bool_option = Unix.socket_bool_option =
# | SO_DEBUG
# | SO_BROADCAST
# | SO_REUSEADDR
# | SO_KEEPALIVE
# | SO_DONTROUTE
# | SO_OOBINLINE
# | SO_ACCEPTCONN
# | TCP_NODELAY
# | IPV6_ONLY
#
type socket_int_option = Unix.socket_int_option =
# | SO_SNDBUF
# | SO_RCVBUF
# | SO_ERROR
# | SO_TYPE
# | SO_RCVLOWAT
# | SO_SNDLOWAT
#
type socket_optint_option = Unix.socket_optint_option =
# | SO_LINGER
#
type socket_float_option = Unix.socket_float_option =
# | SO_RCVTIMEO
# | SO_SNDTIMEO
#
val getsockopt : file_descr -> socket_bool_option -> bool

Wrapper for Unix.getsockopt

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

Wrapper for Unix.setsockopt

#
val getsockopt_int : file_descr -> socket_int_option -> int

Wrapper for Unix.getsockopt_int

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

Wrapper for Unix.setsockopt_int

#
val getsockopt_optint : file_descr -> socket_optint_option -> int option

Wrapper for Unix.getsockopt_optint

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

Wrapper for Unix.setsockopt_optint

#
val getsockopt_float : file_descr -> socket_float_option -> float

Wrapper for Unix.getsockopt_float

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

Wrapper for Unix.setsockopt_float

#
val getsockopt_error : file_descr -> Unix.error option

Wrapper for Unix.getsockopt_error

Host and protocol databases

#
type host_entry = Unix.host_entry = {
# h_name
: string;
# h_aliases
: string array;
# h_addrtype
: socket_domain;
# h_addr_list
: inet_addr array;
}
#
type protocol_entry = Unix.protocol_entry = {
# p_name
: string;
# p_aliases
: string array;
# p_proto
: int;
}
#
type service_entry = Unix.service_entry = {
# s_name
: string;
# s_aliases
: string array;
# s_port
: int;
# s_proto
: string;
}
#
val gethostname : unit -> string Lwt.t

Wrapper for Unix.gethostname

#
val gethostbyname : string -> host_entry Lwt.t

Wrapper for Unix.gethostbyname

#
val gethostbyaddr : inet_addr -> host_entry Lwt.t

Wrapper for Unix.gethostbyaddr

#
val getprotobyname : string -> protocol_entry Lwt.t

Wrapper for Unix.getprotobyname

#
val getprotobynumber : int -> protocol_entry Lwt.t

Wrapper for Unix.getprotobynumber

#
val getservbyname : string -> string -> service_entry Lwt.t

Wrapper for Unix.getservbyname

#
val getservbyport : int -> string -> service_entry Lwt.t

Wrapper for Unix.getservbyport

#
type addr_info = Unix.addr_info = {
# ai_family
: socket_domain;
# ai_socktype
: socket_type;
# ai_protocol
: int;
# ai_addr
: sockaddr;
# ai_canonname
: string;
}
#
type getaddrinfo_option = Unix.getaddrinfo_option =
# | AI_FAMILY of socket_domain
# | AI_SOCKTYPE of socket_type
# | AI_PROTOCOL of int
# | AI_NUMERICHOST
# | AI_CANONNAME
# | AI_PASSIVE
#
val getaddrinfo : string -> string -> getaddrinfo_option list -> addr_info list Lwt.t

Wrapper for Unix.getaddrinfo

#
type name_info = Unix.name_info = {
# ni_hostname
: string;
# ni_service
: string;
}
#
type getnameinfo_option = Unix.getnameinfo_option =
# | NI_NOFQDN
# | NI_NUMERICHOST
# | NI_NAMEREQD
# | NI_NUMERICSERV
# | NI_DGRAM
#
val getnameinfo : sockaddr -> getnameinfo_option list -> name_info Lwt.t

Wrapper for Unix.getnameinfo

Terminal interface

#
type terminal_io = Unix.terminal_io = {
# mutable c_ignbrk
: bool;
# mutable c_brkint
: bool;
# mutable c_ignpar
: bool;
# mutable c_parmrk
: bool;
# mutable c_inpck
: bool;
# mutable c_istrip
: bool;
# mutable c_inlcr
: bool;
# mutable c_igncr
: bool;
# mutable c_icrnl
: bool;
# mutable c_ixon
: bool;
# mutable c_ixoff
: bool;
# mutable c_opost
: bool;
# mutable c_obaud
: int;
# mutable c_ibaud
: int;
# mutable c_csize
: int;
# mutable c_cstopb
: int;
# mutable c_cread
: bool;
# mutable c_parenb
: bool;
# mutable c_parodd
: bool;
# mutable c_hupcl
: bool;
# mutable c_clocal
: bool;
# mutable c_isig
: bool;
# mutable c_icanon
: bool;
# mutable c_noflsh
: bool;
# mutable c_echo
: bool;
# mutable c_echoe
: bool;
# mutable c_echok
: bool;
# mutable c_echonl
: bool;
# mutable c_vintr
: char;
# mutable c_vquit
: char;
# mutable c_verase
: char;
# mutable c_vkill
: char;
# mutable c_veof
: char;
# mutable c_veol
: char;
# mutable c_vmin
: int;
# mutable c_vtime
: int;
# mutable c_vstart
: char;
# mutable c_vstop
: char;
}
#
val tcgetattr : file_descr -> terminal_io Lwt.t

Wrapper for Unix.tcgetattr

#
type setattr_when = Unix.setattr_when =
# | TCSANOW
# | TCSADRAIN
# | TCSAFLUSH
#
val tcsetattr : file_descr -> setattr_when -> terminal_io -> unit Lwt.t

Wrapper for Unix.tcsetattr

#
val tcsendbreak : file_descr -> int -> unit Lwt.t

Wrapper for Unix.tcsendbreak

#
val tcdrain : file_descr -> unit Lwt.t

Wrapper for Unix.tcdrain

#
type flush_queue = Unix.flush_queue =
# | TCIFLUSH
# | TCOFLUSH
# | TCIOFLUSH
#
val tcflush : file_descr -> flush_queue -> unit Lwt.t

Wrapper for Unix.tcflush

#
type flow_action = Unix.flow_action =
# | TCOOFF
# | TCOON
# | TCIOFF
# | TCION
#
val tcflow : file_descr -> flow_action -> unit Lwt.t

Wrapper for Unix.tcflow

Low-level interaction

#
exception Retry

If an action raises Retry, it will be requeued until the file descriptor becomes readable/writable again.

#
exception Retry_read

If an action raises Retry_read, it will be requeued until the file descriptor becomes readable.

#
exception Retry_write

If an action raises Retry_read, it will be requeued until the file descriptor becomes writables.

#
type io_event =
# | Read
# | Write
#
val wrap_syscall : io_event -> file_descr -> (unit -> 'a) -> 'a Lwt.t

wrap_syscall set fd action wrap an action on a file descriptor. It tries to execture action, and if it can not be performed immediately without blocking, it is registered for latter.

In the latter case, if the thread is canceled, action is removed from set.

#
val check_descriptor : file_descr -> unit

check_descriptor fd raise an exception if fd is not in the state [root:Open]

#
val register_action : io_event -> file_descr -> (unit -> 'a) -> 'a Lwt.t

register_action set fd action registers action on fd. When fd becomes readable/writable action is called.

Note:

  • you must call check_descriptor fd before calling register_action
#
type 'a job

Type of job descriptions. A job description describe how to call a C function and how to get its result. The C function may be executed in another system thread.

#
val execute_job : ?async_method:async_method -> job:'a job -> result:('a job -> 'b) -> free:('a job -> unit) -> 'b Lwt.t

This is the old and deprecated way of running a job. Use run_job in new code.

#
val run_job : ?async_method:async_method -> 'a job -> 'a Lwt.t

run_job ?async_method job starts job and wait for its termination.

The async method is choosen follow:

  • if the optional parameter async_method is specified, it is used,
  • otherwise if the local key async_method_key is set in the current thread, it is used,
  • otherwise the default method (returned by default_async_method) is used.

If the method is Async_none then the job is run synchronously and may block the current system thread, thus blocking all Lwt threads.

If the method is Async_detach then the job is run in another system thread, unless the the maximum number of worker threads has been reached (as given by pool_size).

If the method is Async_switch then the job is run synchronously and if it blocks, execution will continue in another system thread (unless the limit is reached).

#
val abort_jobs : exn -> unit

abort_jobs exn make all pending jobs to fail with exn. Note that this does not abort the real job (i.e. the C function executing it), just the lwt thread for it.

#
val cancel_jobs : unit -> unit

cancel_jobs () is the same as abort_jobs Lwt.Canceled.

#
val wait_for_jobs : unit -> unit Lwt.t

Wait for all pending jobs to terminate.

Notifications

Lwt internally use a pipe to send notification to the main thread. The following functions allow to use this pipe.

#
val make_notification : ?once:bool -> (unit -> unit) -> int

new_notifier ?once f registers a new notifier. It returns the id of the notifier. Each time a notification with this id is received, f is called.

if once is specified, then the notification is stopped after the first time it is received. It defaults to false.

#
val send_notification : int -> unit

send_notification id sends a notification.

This function is thread-safe.

#
val stop_notification : int -> unit

Stop the given notification. Note that you should not reuse the id after the notification has been stopped, the result is unspecified if you do so.

#
val call_notification : int -> unit

Call the handler associated to the given notification. Note that if the notification was defined with once = true it is removed.

#
val set_notification : int -> (unit -> unit) -> unit

set_notification id f replace the function associated to the notification by f. It raises Not_found if the given notification is not found.

System threads pool

If the program is using the async method Async_detach or Async_switch, Lwt will launch system threads to execute blocking system calls asynchronously.

#
val pool_size : unit -> int

Maximum number of system threads that can be started. If this limit is reached, jobs will be executed synchronously.

#
val set_pool_size : int -> unit

Change the size of the pool.

#
val thread_count : unit -> int

The number of system threads running (excluding this one).

#
val thread_waiting_count : unit -> int

The number threads waiting for a job.

CPUs

#
val get_cpu : unit -> int

get_cpu () returns the number of the CPU the current thread is running on.

#
val get_affinity : ?pid:int -> unit -> int list

get_affinity ?pid () returns the list of CPUs the process with pid pid is allowed to run on. If pid is not specified then the affinity of the current process is returned.

#
val set_affinity : ?pid:int -> int list -> unit

set_affinity ?pid cpus sets the list of CPUs the given process is allowed to run on.

end