Module Lwt_unix
module Lwt_unix : sig..end
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(* <<div class="odocwiki_info"|~System calls are made synchronously~, and may block the entire program~. >> *) | Async_detach(* <<div class="odocwiki_info"|~System calls are made in another system thread~, thus without blocking other ~Lwt threads~. ~The drawback is that it may degrade performance in some cases~. ~This is the default~. >> *) | Async_switch(* <<div class="odocwiki_info"|~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 <<span class="odocwiki_inlinecode"|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) fval with_async_detach : (unit -> 'a) -> 'a
with_async_none f is a shorthand for:
Lwt.with_value async_method_key (Some Async_detach) fval with_async_switch : (unit -> 'a) -> 'a
with_async_none f is a shorthand for:
Lwt.with_value async_method_key (Some Async_switch) fSleeping ¶
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 Lwt_unix.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(* <<div class="odocwiki_info"|~The **file descriptor** is opened >> *) | Closed(* <<div class="odocwiki_info"|~The **file descriptor** has been closed by <<a_api | val Lwt_unix.close >>~. ~It must not be used for any operation~. >> *) | Aborted of exn(* <<div class="odocwiki_info"|~The **file descriptor** has been aborted~, the only operation possible is <<a_api | val Lwt_unix.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 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 Lwt_unix.stdout, Lwt_unix.stderr or Lwt_unix.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 Lwt_unix.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;(* <<div class="odocwiki_info"|~User time used >> *) ru_stime: float;(* <<div class="odocwiki_info"|~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 -> Bytes.t -> int -> int -> int Lwt.t
read fd buf ofs len has the same semantic as Unix.read, but is cooperative
val write : file_descr -> Bytes.t -> int -> int -> int Lwt.t
write fd buf ofs len has the same semantic as Unix.write, but is cooperative
val write_string : file_descr -> string -> int -> int -> int Lwt.t
See Lwt_unix.write.
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; st_nlink: 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..end
Operations on file names ¶
val unlink : string -> unit Lwt.t
Wrapper for Unix.unlink
val rename : string -> string -> unit Lwt.t
Wrapper for Unix.rename
val link : string -> string -> unit Lwt.t
Wrapper for Unix.link
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 Lwt_unix.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 Lwt_unix.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 ¶
val symlink : string -> string -> unit Lwt.t
Wrapper for Unix.symlink
val readlink : string -> string Lwt.t
Wrapper for Unix.readlink
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 Lwt_unix.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:
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 ->
Bytes.t -> int -> int -> msg_flag list -> int Lwt.t
Wrapper for Unix.recv
val recvfrom :
file_descr ->
Bytes.t ->
int ->
int -> msg_flag list -> (int * sockaddr) Lwt.t
Wrapper for Unix.recvfrom
val send :
file_descr ->
Bytes.t -> int -> int -> msg_flag list -> int Lwt.t
Wrapper for Unix.send
val sendto :
file_descr ->
Bytes.t ->
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 Lwt_unix.recv_msg and Lwt_unix.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 credentials information 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 Lwt_unix.Retry, it will be requeued until the file descriptor becomes readable/writable again.
exception Retry_read
If an action raises Lwt_unix.Retry_read, it will be requeued until the file descriptor becomes readable.
exception Retry_write
If an action raises Lwt_unix.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 execute action, and if it can not be performed immediately without blocking, it is registered for later.
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 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
- you should prefer using Lwt_unix.wrap_syscall
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 Lwt_unix.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 Lwt_unix.async_method_key is set in the current thread, it is used,
- otherwise the default method (returned by Lwt_unix.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 Lwt_unix.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.