package links

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.

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.

Return a string describing the given error code.

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

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.

Return the process environment, as an array of strings with the format ``variable=value''. Unlike environment, this function returns a populated array even if the process has special privileges. See the documentation for unsafe_getenv for more details.

• since 4.06 (4.12 in UnixLabels)

Return the value associated to a variable in the process environment.

Unlike 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.

• raises Not_found

  if the variable is unbound.

• since 4.06

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.

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.

Flags for waitpid.

execv prog args execute the program in file prog, with the arguments args, and the current process environment. 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 create_process or one of the open_process_* functions instead is recommended.

• raises Unix_error

  on failure

Same as execv, except that the third argument provides the environment to the program executed.

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

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

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

• raises Invalid_argument

  on Windows. Use create_process or threads instead.

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

• raises Invalid_argument

  on Windows. Use waitpid instead.

Same as 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.

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.

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 Stdlib.exit, Unix._exit performs no finalization whatsoever: functions registered with Stdlib.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

Return the pid of the process.

Return the pid of the parent process.

• raises Invalid_argument

  on Windows (because it is meaningless)

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

The abstract type of file descriptors.

File descriptor for standard input.

File descriptor for standard output.

File descriptor for standard error.

The flags to openfile.

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

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

Close a file descriptor.

Flush file buffers to disk.

• since 4.08 (4.12 in UnixLabels)

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.

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.

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

Same as write, but take the data from a string instead of a byte sequence.

• since 4.02

Same as single_write, but take the data from a string instead of a byte sequence.

• since 4.02

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: Stdlib.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.

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: Stdlib.set_binary_mode_out always fails on channels created with this function.

Beware that output channels are buffered, so you may have to call Stdlib.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.

Return the descriptor corresponding to an input channel.

Return the descriptor corresponding to an output channel.

Positioning modes for lseek.

Set the current position for a file descriptor, and return the resulting offset (from the beginning of the file).

Truncates the named file to the given size.

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

The information returned by the stat calls.

Return the information for the named file.

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

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

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

File operations on large files. This sub-module provides 64-bit variants of the functions lseek (for positioning a file descriptor), truncate and ftruncate (for changing the size of a file), and stat, lstat and 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.

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 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.

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. 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

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

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.

link ?follow src dst creates a hard link named dst to the file named src.

• parameter follow

  indicates whether a src symlink is followed or a hardlink to src itself will be created. On Unix systems this is done using the linkat(2) function. If ?follow is not provided, then the link(2) function is used whose behaviour is OS-dependent, but more widely available.

• raises ENOSYS

  On Unix if ~follow:_ is requested, but linkat is unavailable.

• raises ENOSYS

  On Windows if ~follow:false is requested.

realpath p is an absolute pathname for p obtained by resolving all extra / characters, relative path segments and symbolic links.

• since 4.13

Flags for the access call.

Change the permissions of the named file.

Change the permissions of an opened file.

• raises Invalid_argument

  on Windows

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

• raises Invalid_argument

  on Windows

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

• raises Invalid_argument

  on Windows

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

• raises Invalid_argument

  on Windows

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.

Return a new file descriptor referencing the same file as the given descriptor. See set_close_on_exec for documentation on the cloexec optional argument.

dup2 src dst duplicates src to dst, closing dst if already opened. See set_close_on_exec for documentation on the cloexec optional argument.

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.

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

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.

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

Create a directory with the given permissions (see umask).

Remove an empty directory.

Change the process working directory.

Return the name of the current working directory.

Change the process root directory.

• raises Invalid_argument

  on Windows

The type of descriptors over opened directories.

Open a descriptor on a directory

Return the next entry in a directory.

• raises End_of_file

  when the end of the directory has been reached.

Reposition the descriptor to the beginning of the directory

Close a directory descriptor.

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 set_close_on_exec for documentation on the cloexec optional argument.

Create a named pipe with the given permissions (see umask).

• raises Invalid_argument

  on Windows

create_process prog args stdin stdout stderr creates a new process that executes the program in file prog, with arguments args. The pid of the new process is returned immediately; the new process executes concurrently with the current process. The standard input and outputs of the new process are connected to the descriptors 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.

create_process_env prog args env stdin stdout stderr works as create_process, except that the extra argument env specifies the environment passed to the program.

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. 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, open_process_args_in can be used as a more robust and more efficient alternative to open_process_in.

Same as 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 Stdlib.flush at the right times to ensure correct synchronization. If the command does not need to be run through the shell, open_process_args_out can be used instead of open_process_out.

Same as 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, open_process_args can be used instead of open_process.

Similar to 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, open_process_args_full can be used instead of open_process_full.

open_process_args prog args runs the program prog with arguments args. Note that the first argument 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 Stdlib.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

Same as open_process_args, but redirects only the standard output of the new process.

• since 4.08

Same as open_process_args, but redirects only the standard input of the new process.

• since 4.08

Similar to 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

Return the pid of a process opened via open_process_in or open_process_args_in.

• since 4.08 (4.12 in UnixLabels)

Return the pid of a process opened via open_process_out or open_process_args_out.

• since 4.08 (4.12 in UnixLabels)

Return the pid of a process opened via open_process or open_process_args.

• since 4.08 (4.12 in UnixLabels)

Return the pid of a process opened via open_process_full or open_process_args_full.

• since 4.08 (4.12 in UnixLabels)

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

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

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

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

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.

has_symlink can be used to check that a process is able to create symbolic links.

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

Read the contents of a symbolic link.

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).

Commands for lockf.

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 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.

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

On Windows: only the Sys.sigkill signal is emulated.

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)

Return the set of blocked signals that are currently pending.

• raises Invalid_argument

  on Windows (no inter-process signals on Windows)

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)

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

• raises Invalid_argument

  on Windows (no inter-process signals on Windows)

The execution times (CPU times) of a process.

The type representing wallclock time and calendar date.

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

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

Convert a time in seconds, as returned by 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 mktime, and then restore the original value of TZ.

Convert a time in seconds, as returned by time, into a date and a time. Assumes the local time zone. The function performing the inverse conversion is mktime.

Convert a date and time, specified by the tm argument, into a time in seconds, as returned by 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.

Schedule a SIGALRM signal after the given number of seconds.

• raises Invalid_argument

  on Windows

Stop execution for the given number of seconds.

Stop execution for the given number of seconds. Like sleep, but fractions of seconds are supported.

• since 4.03 (4.12 in UnixLabels)

Return the execution times of the process.

On Windows: partially implemented, will not report timings for child processes.

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.

The three kinds of interval timers.

The type describing the status of an interval timer

Return the current status of the given interval timer.

• raises Invalid_argument

  on Windows

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

Return the user id of the user executing the process.

On Windows: always returns 1.

Return the effective user id under which the process runs.

On Windows: always returns 1.

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

• raises Invalid_argument

  on Windows

Return the group id of the user executing the process.

On Windows: always returns 1.

Return the effective group id under which the process runs.

On Windows: always returns 1.

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

• raises Invalid_argument

  on Windows

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

On Windows: always returns [|1|].

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

• raises Invalid_argument

  on Windows

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

Structure of entries in the passwd database.

Structure of entries in the groups database.

Return the login name of the user executing the process.

The abstract type of Internet addresses.

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.

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

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

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

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

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

Whether the given inet_addr is an IPv6 address.

• since 4.12

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.

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.

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.

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 set_close_on_exec for documentation on the cloexec optional argument.

Return the socket domain adequate for the given socket address.

Create a pair of unnamed sockets, connected together. See set_close_on_exec for documentation on the cloexec optional argument.

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 set_close_on_exec for documentation on the cloexec optional argument.

Bind a socket to an address.

Connect a socket to an address.

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

The type of commands for shutdown.

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).

Return the address of the given socket.

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

The flags for recv, recvfrom, send and sendto.

Receive data from a connected socket.

Receive data from an unconnected socket.

Send data over a connected socket.

Same as send, but take the data from a string instead of a byte sequence.

• since 4.02

Send data over an unconnected socket.

Same as sendto, but take the data from a string instead of a byte sequence.

• since 4.02

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

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

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

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

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

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

Same as getsockopt for an integer-valued socket option.

Same as setsockopt for an integer-valued socket option.

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

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

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

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

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

Connect to a server at the given address. Return a pair of buffered channels connected to the server. Remember to call Stdlib.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 Stdlib.close_out on the output channel, which will also close the underlying socket. Do not call Stdlib.close_in on the input channel; it will be collected by the GC eventually.

``Shut down'' a connection established with 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.

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 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 Stdlib.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.

Structure of entries in the hosts database.

Structure of entries in the protocols database.

Structure of entries in the services database.

Return the name of the local host.

Address information returned by getaddrinfo.

Options to getaddrinfo.

getaddrinfo host service opts returns a list of 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).

Host and service information returned by getnameinfo.

Options to getnameinfo.

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

• raises Invalid_argument

  on Windows

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

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

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

• raises Invalid_argument

  on Windows

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

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

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

• raises Invalid_argument

  on Windows