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Standard Library

Below is the API for the OCaml standard library. It's directly copied over from the OCaml Manual, formatted to the Reason syntax and styled accordingly. The API docs are work-in-progress; we'll be polishing these gradually!

If you're targeting JavaScript, the API docs for BuckleScript includes all of below, plus JS-specific APIs.

Module Unix

module Unix: sig .. end
Interface to the Unix system.

Note: all the functions of this module (except error_message and handle_unix_error) are liable to raise the Unix_error exception whenever the underlying system call signals an error.



Error report

type error = 
| E2BIG (*
Argument list too long
*)
| EACCES (*
Permission denied
*)
| EAGAIN (*
Resource temporarily unavailable; try again
*)
| EBADF (*
Bad file descriptor
*)
| EBUSY (*
Resource unavailable
*)
| ECHILD (*
No child process
*)
| EDEADLK (*
Resource deadlock would occur
*)
| EDOM (*
Domain error for math functions, etc.
*)
| EEXIST (*
File exists
*)
| EFAULT (*
Bad address
*)
| EFBIG (*
File too large
*)
| EINTR (*
Function interrupted by signal
*)
| EINVAL (*
Invalid argument
*)
| EIO (*
Hardware I/O error
*)
| EISDIR (*
Is a directory
*)
| EMFILE (*
Too many open files by the process
*)
| EMLINK (*
Too many links
*)
| ENAMETOOLONG (*
Filename too long
*)
| ENFILE (*
Too many open files in the system
*)
| ENODEV (*
No such device
*)
| ENOENT (*
No such file or directory
*)
| ENOEXEC (*
Not an executable file
*)
| ENOLCK (*
No locks available
*)
| ENOMEM (*
Not enough memory
*)
| ENOSPC (*
No space left on device
*)
| ENOSYS (*
Function not supported
*)
| ENOTDIR (*
Not a directory
*)
| ENOTEMPTY (*
Directory not empty
*)
| ENOTTY (*
Inappropriate I/O control operation
*)
| ENXIO (*
No such device or address
*)
| EPERM (*
Operation not permitted
*)
| EPIPE (*
Broken pipe
*)
| ERANGE (*
Result too large
*)
| EROFS (*
Read-only file system
*)
| ESPIPE (*
Invalid seek e.g. on a pipe
*)
| ESRCH (*
No such process
*)
| EXDEV (*
Invalid link
*)
| EWOULDBLOCK (*
Operation would block
*)
| EINPROGRESS (*
Operation now in progress
*)
| EALREADY (*
Operation already in progress
*)
| ENOTSOCK (*
Socket operation on non-socket
*)
| EDESTADDRREQ (*
Destination address required
*)
| EMSGSIZE (*
Message too long
*)
| EPROTOTYPE (*
Protocol wrong type for socket
*)
| ENOPROTOOPT (*
Protocol not available
*)
| EPROTONOSUPPORT (*
Protocol not supported
*)
| ESOCKTNOSUPPORT (*
Socket type not supported
*)
| EOPNOTSUPP (*
Operation not supported on socket
*)
| EPFNOSUPPORT (*
Protocol family not supported
*)
| EAFNOSUPPORT (*
Address family not supported by protocol family
*)
| EADDRINUSE (*
Address already in use
*)
| EADDRNOTAVAIL (*
Can't assign requested address
*)
| ENETDOWN (*
Network is down
*)
| ENETUNREACH (*
Network is unreachable
*)
| ENETRESET (*
Network dropped connection on reset
*)
| ECONNABORTED (*
Software caused connection abort
*)
| ECONNRESET (*
Connection reset by peer
*)
| ENOBUFS (*
No buffer space available
*)
| EISCONN (*
Socket is already connected
*)
| ENOTCONN (*
Socket is not connected
*)
| ESHUTDOWN (*
Can't send after socket shutdown
*)
| ETOOMANYREFS (*
Too many references: can't splice
*)
| ETIMEDOUT (*
Connection timed out
*)
| ECONNREFUSED (*
Connection refused
*)
| EHOSTDOWN (*
Host is down
*)
| EHOSTUNREACH (*
No route to host
*)
| ELOOP (*
Too many levels of symbolic links
*)
| EOVERFLOW (*
File size or position not representable
*)
| EUNKNOWNERR of int (*
Unknown error
*)
The type of error codes. Errors defined in the POSIX standard and additional errors from UNIX98 and BSD. All other errors are mapped to EUNKNOWNERR.
exception Unix_error(error, string, string);
Raised by the system calls below when an error is encountered. The first component is the error code; the second component is the function name; the third component is the string parameter to the function, if it has one, or the empty string otherwise.
let error_message: error => string;
Return a string describing the given error code.
let handle_unix_error: ('a => 'b, 'a) => 'b;
handle_unix_error f x applies f to x and returns the result. If the exception Unix_error is raised, it prints a message describing the error and exits with code 2.

Access to the process environment

let environment: unit => array(string);
Return the process environment, as an array of strings with the format ``variable=value''.
let getenv: string => string;
Return the value associated to a variable in the process environment. Raise Not_found if the variable is unbound. (This function is identical to Sys.getenv.)
let putenv: (string, string) => unit;
Unix.putenv name value sets the value associated to a variable in the process environment. name is the name of the environment variable, and value its new associated value.

Process handling

type process_status = 
| WEXITED of int (*
The process terminated normally by exit; the argument is the return code.
*)
| WSIGNALED of int (*
The process was killed by a signal; the argument is the signal number.
*)
| WSTOPPED of int (*
The process was stopped by a signal; the argument is the signal number.
*)
The termination status of a process. See module Sys for the definitions of the standard signal numbers. Note that they are not the numbers used by the OS.
type wait_flag = 
| WNOHANG (*
do not block if no child has died yet, but immediately return with a pid equal to 0.
*)
| WUNTRACED (*
report also the children that receive stop signals.
*)
Flags for Unix.waitpid.
let execv: (string, array(string)) => 'a;
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 failure, a Unix.Unix_error exception is raised.
let execve: (string, array(string), array(string)) => 'a;
Same as Unix.execv, except that the third argument provides the environment to the program executed.
let execvp: (string, array(string)) => 'a;
Same as Unix.execv, except that the program is searched in the path.
let execvpe: (string, array(string), array(string)) => 'a;
Same as Unix.execve, except that the program is searched in the path.
let fork: unit => int;
Fork a new process. The returned integer is 0 for the child process, the pid of the child process for the parent process.
let wait: unit => (int, process_status);
Wait until one of the children processes die, and return its pid and termination status.
let waitpid: (list(wait_flag), int) => (int, process_status);
Same as Unix.wait, but waits for the child process whose pid is given. A pid of -1 means wait for any child. A pid of 0 means wait for any child in the same process group as the current process. Negative pid arguments represent process groups. The list of options indicates whether waitpid should return immediately without waiting, and whether it should report stopped children.
let system: string => process_status;
Execute the given command, wait until it terminates, and return its termination status. The string is interpreted by the shell /bin/sh and therefore can contain redirections, quotes, variables, etc. The result WEXITED 127 indicates that the shell couldn't be executed.
let getpid: unit => int;
Return the pid of the process.
let getppid: unit => int;
Return the pid of the parent process.
let nice: int => int;
Change the process priority. The integer argument is added to the ``nice'' value. (Higher values of the ``nice'' value mean lower priorities.) Return the new nice value.

Basic file input/output

type file_descr;
The abstract type of file descriptors.
let stdin: file_descr;
File descriptor for standard input.
let stdout: file_descr;
File descriptor for standard output.
let stderr: file_descr;
File descriptor for standard error.
type open_flag = 
| O_RDONLY (*
Open for reading
*)
| O_WRONLY (*
Open for writing
*)
| O_RDWR (*
Open for reading and writing
*)
| O_NONBLOCK (*
Open in non-blocking mode
*)
| O_APPEND (*
Open for append
*)
| O_CREAT (*
Create if nonexistent
*)
| O_TRUNC (*
Truncate to 0 length if existing
*)
| O_EXCL (*
Fail if existing
*)
| O_NOCTTY (*
Don't make this dev a controlling tty
*)
| O_DSYNC (*
Writes complete as `Synchronised I/O data integrity completion'
*)
| O_SYNC (*
Writes complete as `Synchronised I/O file integrity completion'
*)
| O_RSYNC (*
Reads complete as writes (depending on O_SYNC/O_DSYNC)
*)
| O_SHARE_DELETE (*
Windows only: allow the file to be deleted while still open
*)
| O_CLOEXEC (*
Set the close-on-exec flag on the descriptor returned by Unix.openfile
*)
The flags to Unix.openfile.
type file_perm = int;
The type of file access rights, e.g. 0o640 is read and write for user, read for group, none for others
let openfile: (string, list(open_flag), file_perm) => file_descr;
Open the named file with the given flags. Third argument is the permissions to give to the file if it is created (see Unix.umask). Return a file descriptor on the named file.
let close: file_descr => unit;
Close a file descriptor.
let read: (file_descr, bytes, int, int) => int;
read fd buff ofs len reads len bytes from descriptor fd, storing them in byte sequence buff, starting at position ofs in buff. Return the number of bytes actually read.
let write: (file_descr, bytes, int, int) => int;
write fd buff ofs len writes len bytes to descriptor fd, taking them from byte sequence buff, starting at position ofs in buff. Return the number of bytes actually written. write repeats the writing operation until all bytes have been written or an error occurs.
let single_write: (file_descr, bytes, int, int) => int;
Same as write, but attempts to write only once. Thus, if an error occurs, single_write guarantees that no data has been written.
let write_substring: (file_descr, string, int, int) => int;
Same as write, but take the data from a string instead of a byte sequence.
let single_write_substring: (file_descr, string, int, int) => int;
Same as single_write, but take the data from a string instead of a byte sequence.

Interfacing with the standard input/output library

let in_channel_of_descr: file_descr => Pervasives.in_channel;
Create an input channel reading from the given descriptor. The channel is initially in binary mode; use set_binary_mode_in ic false if text mode is desired.
let out_channel_of_descr: file_descr => Pervasives.out_channel;
Create an output channel writing on the given descriptor. The channel is initially in binary mode; use set_binary_mode_out oc false if text mode is desired.
let descr_of_in_channel: Pervasives.in_channel => file_descr;
Return the descriptor corresponding to an input channel.
let descr_of_out_channel: Pervasives.out_channel => file_descr;
Return the descriptor corresponding to an output channel.

Seeking and truncating

type seek_command = 
| SEEK_SET (*
indicates positions relative to the beginning of the file
*)
| SEEK_CUR (*
indicates positions relative to the current position
*)
| SEEK_END (*
indicates positions relative to the end of the file
*)
Positioning modes for Unix.lseek.
let lseek: (file_descr, int, seek_command) => int;
Set the current position for a file descriptor, and return the resulting offset (from the beginning of the file).
let truncate: (string, int) => unit;
Truncates the named file to the given size.
let ftruncate: (file_descr, int) => unit;
Truncates the file corresponding to the given descriptor to the given size.

File status

type file_kind = 
| S_REG (*
Regular file
*)
| S_DIR (*
Directory
*)
| S_CHR (*
Character device
*)
| S_BLK (*
Block device
*)
| S_LNK (*
Symbolic link
*)
| S_FIFO (*
Named pipe
*)
| S_SOCK (*
Socket
*)
type stats = {
   st_dev : int; (*
Device number
*)
   st_ino : int; (*
Inode number
*)
   st_kind : file_kind; (*
Kind of the file
*)
   st_perm : file_perm; (*
Access rights
*)
   st_nlink : int; (*
Number of links
*)
   st_uid : int; (*
User id of the owner
*)
   st_gid : int; (*
Group ID of the file's group
*)
   st_rdev : int; (*
Device minor number
*)
   st_size : int; (*
Size in bytes
*)
   st_atime : float; (*
Last access time
*)
   st_mtime : float; (*
Last modification time
*)
   st_ctime : float; (*
Last status change time
*)
}
The information returned by the Unix.stat calls.
let stat: string => stats;
Return the information for the named file.
let lstat: string => stats;
Same as Unix.stat, but in case the file is a symbolic link, return the information for the link itself.
let fstat: file_descr => stats;
Return the information for the file associated with the given descriptor.
let isatty: file_descr => bool;
Return true if the given file descriptor refers to a terminal or console window, false otherwise.

File operations on large files

module LargeFile: sig .. end
File operations on large files.

Operations on file names

Removes the named file
let rename: (string, string) => unit;
rename old new changes the name of a file from old to new.
link source dest creates a hard link named dest to the file named source.

File permissions and ownership

type access_permission = 
| R_OK (*
Read permission
*)
| W_OK (*
Write permission
*)
| X_OK (*
Execution permission
*)
| F_OK (*
File exists
*)
Flags for the Unix.access call.
let chmod: (string, file_perm) => unit;
Change the permissions of the named file.
let fchmod: (file_descr, file_perm) => unit;
Change the permissions of an opened file.
let chown: (string, int, int) => unit;
Change the owner uid and owner gid of the named file.
let fchown: (file_descr, int, int) => unit;
Change the owner uid and owner gid of an opened file.
let umask: int => int;
Set the process's file mode creation mask, and return the previous mask.
let access: (string, list(access_permission)) => unit;
Check that the process has the given permissions over the named file. Raise Unix_error otherwise.

Operations on file descriptors

let dup: file_descr => file_descr;
Return a new file descriptor referencing the same file as the given descriptor.
let dup2: (file_descr, file_descr) => unit;
dup2 fd1 fd2 duplicates fd1 to fd2, closing fd2 if already opened.
let set_nonblock: file_descr => unit;
Set the ``non-blocking'' flag on the given descriptor. When the non-blocking flag is set, reading on a descriptor on which there is temporarily no data available raises the EAGAIN or EWOULDBLOCK error instead of blocking; writing on a descriptor on which there is temporarily no room for writing also raises EAGAIN or EWOULDBLOCK.
let clear_nonblock: file_descr => unit;
Clear the ``non-blocking'' flag on the given descriptor. See Unix.set_nonblock.
let set_close_on_exec: file_descr => unit;
Set the ``close-on-exec'' flag on the given descriptor. A descriptor with the close-on-exec flag is automatically closed when the current process starts another program with one of the exec functions.
let clear_close_on_exec: file_descr => unit;
Clear the ``close-on-exec'' flag on the given descriptor. See Unix.set_close_on_exec.

Directories

let mkdir: (string, file_perm) => unit;
Create a directory with the given permissions (see Unix.umask).
let rmdir: string => unit;
Remove an empty directory.
let chdir: string => unit;
Change the process working directory.
let getcwd: unit => string;
Return the name of the current working directory.
let chroot: string => unit;
Change the process root directory.
type dir_handle;
The type of descriptors over opened directories.
let opendir: string => dir_handle;
Open a descriptor on a directory
let readdir: dir_handle => string;
Return the next entry in a directory.
Raises End_of_file when the end of the directory has been reached.
let rewinddir: dir_handle => unit;
Reposition the descriptor to the beginning of the directory
let closedir: dir_handle => unit;
Close a directory descriptor.

Pipes and redirections

let pipe: unit => (file_descr, file_descr);
Create a pipe. The first component of the result is opened for reading, that's the exit to the pipe. The second component is opened for writing, that's the entrance to the pipe.
let mkfifo: (string, file_perm) => unit;
Create a named pipe with the given permissions (see Unix.umask).

High-level process and redirection management

let create_process: (string, array(string), file_descr, file_descr, file_descr) => int;
create_process prog args new_stdin new_stdout new_stderr forks a new process that executes the program in file prog, with arguments args. The pid of the new process is returned immediately; the new process executes concurrently with the current process. The standard input and outputs of the new process are connected to the descriptors new_stdin, new_stdout and new_stderr. Passing e.g. stdout for new_stdout prevents the redirection and causes the new process to have the same standard output as the current process. The executable file prog is searched in the path. The new process has the same environment as the current process.
let create_process_env:
  (string, array(string), array(string), file_descr, file_descr, file_descr) => int;
create_process_env prog args env new_stdin new_stdout new_stderr works as Unix.create_process, except that the extra argument env specifies the environment passed to the program.
let open_process_in: string => Pervasives.in_channel;
High-level pipe and process management. This function runs the given command in parallel with the program. The standard output of the command is redirected to a pipe, which can be read via the returned input channel. The command is interpreted by the shell /bin/sh (cf. system).
let open_process_out: string => Pervasives.out_channel;
Same as Unix.open_process_in, but redirect the standard input of the command to a pipe. Data written to the returned output channel is sent to the standard input of the command. Warning: writes on output channels are buffered, hence be careful to call Pervasives.flush at the right times to ensure correct synchronization.
let open_process: string => (Pervasives.in_channel, Pervasives.out_channel);
Same as Unix.open_process_out, but redirects both the standard input and standard output of the command to pipes connected to the two returned channels. The input channel is connected to the output of the command, and the output channel to the input of the command.
let open_process_full:
  (string, array(string)) => (Pervasives.in_channel, Pervasives.out_channel, Pervasives.in_channel);
Similar to Unix.open_process, but the second argument specifies the environment passed to the command. The result is a triple of channels connected respectively to the standard output, standard input, and standard error of the command.
let close_process_in: Pervasives.in_channel => process_status;
Close channels opened by Unix.open_process_in, wait for the associated command to terminate, and return its termination status.
let close_process_out: Pervasives.out_channel => process_status;
Close channels opened by Unix.open_process_out, wait for the associated command to terminate, and return its termination status.
let close_process: ((Pervasives.in_channel, Pervasives.out_channel)) => process_status;
Close channels opened by Unix.open_process, wait for the associated command to terminate, and return its termination status.
let close_process_full:
  ((Pervasives.in_channel, Pervasives.out_channel, Pervasives.in_channel)) => process_status;
Close channels opened by Unix.open_process_full, wait for the associated command to terminate, and return its termination status.


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

Polling

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

Locking

type lock_command = 
| F_ULOCK (*
Unlock a region
*)
| F_LOCK (*
Lock a region for writing, and block if already locked
*)
| F_TLOCK (*
Lock a region for writing, or fail if already locked
*)
| F_TEST (*
Test a region for other process locks
*)
| F_RLOCK (*
Lock a region for reading, and block if already locked
*)
| F_TRLOCK (*
Lock a region for reading, or fail if already locked
*)
Commands for Unix.lockf.
let lockf: (file_descr, lock_command, int) => unit;
lockf fd cmd size puts a lock on a region of the file opened as fd. The region starts at the current read/write position for fd (as set by Unix.lseek), and extends size bytes forward if size is positive, size bytes backwards if size is negative, or to the end of the file if size is zero. A write lock prevents any other process from acquiring a read or write lock on the region. A read lock prevents any other process from acquiring a write lock on the region, but lets other processes acquire read locks on it.

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


Signals
Note: installation of signal handlers is performed via the functions Sys.signal and Sys.set_signal.
let kill: (int, int) => unit;
kill pid sig sends signal number sig to the process with id pid. Under Windows, only the Sys.sigkill signal is emulated.
type sigprocmask_command = 
| SIG_SETMASK
| SIG_BLOCK
| SIG_UNBLOCK
let sigprocmask: (sigprocmask_command, list(int)) => list(int);
sigprocmask cmd sigs changes the set of blocked signals. If cmd is SIG_SETMASK, blocked signals are set to those in the list sigs. If cmd is SIG_BLOCK, the signals in sigs are added to the set of blocked signals. If cmd is SIG_UNBLOCK, the signals in sigs are removed from the set of blocked signals. sigprocmask returns the set of previously blocked signals.
let sigpending: unit => list(int);
Return the set of blocked signals that are currently pending.
let sigsuspend: list(int) => unit;
sigsuspend sigs atomically sets the blocked signals to sigs and waits for a non-ignored, non-blocked signal to be delivered. On return, the blocked signals are reset to their initial value.
let pause: unit => unit;
Wait until a non-ignored, non-blocked signal is delivered.

Time functions

type process_times = {
   tms_utime : float; (*
User time for the process
*)
   tms_stime : float; (*
System time for the process
*)
   tms_cutime : float; (*
User time for the children processes
*)
   tms_cstime : float; (*
System time for the children processes
*)
}
The execution times (CPU times) of a process.
type tm = {
   tm_sec : int; (*
Seconds 0..60
*)
   tm_min : int; (*
Minutes 0..59
*)
   tm_hour : int; (*
Hours 0..23
*)
   tm_mday : int; (*
Day of month 1..31
*)
   tm_mon : int; (*
Month of year 0..11
*)
   tm_year : int; (*
Year - 1900
*)
   tm_wday : int; (*
Day of week (Sunday is 0)
*)
   tm_yday : int; (*
Day of year 0..365
*)
   tm_isdst : bool; (*
Daylight time savings in effect
*)
}
The type representing wallclock time and calendar date.
let time: unit => float;
Return the current time since 00:00:00 GMT, Jan. 1, 1970, in seconds.
let gettimeofday: unit => float;
Same as Unix.time, but with resolution better than 1 second.
let gmtime: float => tm;
Convert a time in seconds, as returned by Unix.time, into a date and a time. Assumes UTC (Coordinated Universal Time), also known as GMT.
let localtime: float => tm;
Convert a time in seconds, as returned by Unix.time, into a date and a time. Assumes the local time zone.
let mktime: tm => (float, tm);
Convert a date and time, specified by the tm argument, into a time in seconds, as returned by Unix.time. The tm_isdst, tm_wday and tm_yday fields of tm are ignored. Also return a normalized copy of the given tm record, with the tm_wday, tm_yday, and tm_isdst fields recomputed from the other fields, and the other fields normalized (so that, e.g., 40 October is changed into 9 November). The tm argument is interpreted in the local time zone.
let alarm: int => int;
Schedule a SIGALRM signal after the given number of seconds.
let sleep: int => unit;
Stop execution for the given number of seconds.
let times: unit => process_times;
Return the execution times of the process.
let utimes: (string, float, float) => unit;
Set the last access time (second arg) and last modification time (third arg) for a file. Times are expressed in seconds from 00:00:00 GMT, Jan. 1, 1970. A time of 0.0 is interpreted as the current time.
type interval_timer = 
| ITIMER_REAL (*
decrements in real time, and sends the signal SIGALRM when expired.
*)
| ITIMER_VIRTUAL (*
decrements in process virtual time, and sends SIGVTALRM when expired.
*)
| ITIMER_PROF (*
(for profiling) decrements both when the process is running and when the system is running on behalf of the process; it sends SIGPROF when expired.
*)
The three kinds of interval timers.
type interval_timer_status = {
   it_interval : float; (*
Period
*)
   it_value : float; (*
Current value of the timer
*)
}
The type describing the status of an interval timer
let getitimer: interval_timer => interval_timer_status;
Return the current status of the given interval timer.
let setitimer: (interval_timer, interval_timer_status) => interval_timer_status;
setitimer t s sets the interval timer t and returns its previous status. The s argument is interpreted as follows: s.it_value, if nonzero, is the time to the next timer expiration; s.it_interval, if nonzero, specifies a value to be used in reloading it_value when the timer expires. Setting s.it_value to zero disables the timer. Setting s.it_interval to zero causes the timer to be disabled after its next expiration.

User id, group id

let getuid: unit => int;
Return the user id of the user executing the process.
let geteuid: unit => int;
Return the effective user id under which the process runs.
let setuid: int => unit;
Set the real user id and effective user id for the process.
let getgid: unit => int;
Return the group id of the user executing the process.
let getegid: unit => int;
Return the effective group id under which the process runs.
let setgid: int => unit;
Set the real group id and effective group id for the process.
let getgroups: unit => array(int);
Return the list of groups to which the user executing the process belongs.
let setgroups: array(int) => unit;
setgroups groups sets the supplementary group IDs for the calling process. Appropriate privileges are required.
let initgroups: (string, int) => unit;
initgroups user group initializes the group access list by reading the group database /etc/group and using all groups of which user is a member. The additional group group is also added to the list.
type passwd_entry = {
   pw_name : string;
   pw_passwd : string;
   pw_uid : int;
   pw_gid : int;
   pw_gecos : string;
   pw_dir : string;
   pw_shell : string;
}
Structure of entries in the passwd database.
type group_entry = {
   gr_name : string;
   gr_passwd : string;
   gr_gid : int;
   gr_mem : string array;
}
Structure of entries in the groups database.
let getlogin: unit => string;
Return the login name of the user executing the process.
let getpwnam: string => passwd_entry;
Find an entry in passwd with the given name, or raise Not_found.
let getgrnam: string => group_entry;
Find an entry in group with the given name, or raise Not_found.
let getpwuid: int => passwd_entry;
Find an entry in passwd with the given user id, or raise Not_found.
let getgrgid: int => group_entry;
Find an entry in group with the given group id, or raise Not_found.

Internet addresses

type inet_addr;
The abstract type of Internet addresses.
let inet_addr_of_string: string => inet_addr;
Conversion from the printable representation of an Internet address to its internal representation. The argument string consists of 4 numbers separated by periods (XXX.YYY.ZZZ.TTT) for IPv4 addresses, and up to 8 numbers separated by colons for IPv6 addresses. Raise Failure when given a string that does not match these formats.
let string_of_inet_addr: inet_addr => string;
Return the printable representation of the given Internet address. See Unix.inet_addr_of_string for a description of the printable representation.
let inet_addr_any: inet_addr;
A special IPv4 address, for use only with bind, representing all the Internet addresses that the host machine possesses.
let inet_addr_loopback: inet_addr;
A special IPv4 address representing the host machine (127.0.0.1).
let inet6_addr_any: inet_addr;
A special IPv6 address, for use only with bind, representing all the Internet addresses that the host machine possesses.
let inet6_addr_loopback: inet_addr;
A special IPv6 address representing the host machine (::1).

Sockets

type socket_domain = 
| PF_UNIX (*
Unix domain
*)
| PF_INET (*
Internet domain (IPv4)
*)
| PF_INET6 (*
Internet domain (IPv6)
*)
The type of socket domains. Not all platforms support IPv6 sockets (type PF_INET6).
type socket_type = 
| SOCK_STREAM (*
Stream socket
*)
| SOCK_DGRAM (*
Datagram socket
*)
| SOCK_RAW (*
Raw socket
*)
| SOCK_SEQPACKET (*
Sequenced packets socket
*)
The type of socket kinds, specifying the semantics of communications.
type sockaddr = 
| ADDR_UNIX of string
| ADDR_INET of inet_addr * int (*
The type of socket addresses. ADDR_UNIX name is a socket address in the Unix domain; name is a file name in the file system. ADDR_INET(addr,port) is a socket address in the Internet domain; addr is the Internet address of the machine, and port is the port number.
*)
let socket: (socket_domain, socket_type, int) => file_descr;
Create a new socket in the given domain, and with the given kind. The third argument is the protocol type; 0 selects the default protocol for that kind of sockets.
let domain_of_sockaddr: sockaddr => socket_domain;
Return the socket domain adequate for the given socket address.
let socketpair: (socket_domain, socket_type, int) => (file_descr, file_descr);
Create a pair of unnamed sockets, connected together.
let accept: file_descr => (file_descr, sockaddr);
Accept connections on the given socket. The returned descriptor is a socket connected to the client; the returned address is the address of the connecting client.
let bind: (file_descr, sockaddr) => unit;
Bind a socket to an address.
let connect: (file_descr, sockaddr) => unit;
Connect a socket to an address.
let listen: (file_descr, int) => unit;
Set up a socket for receiving connection requests. The integer argument is the maximal number of pending requests.
type shutdown_command = 
| SHUTDOWN_RECEIVE (*
Close for receiving
*)
| SHUTDOWN_SEND (*
Close for sending
*)
| SHUTDOWN_ALL (*
Close both
*)
The type of commands for shutdown.
let shutdown: (file_descr, shutdown_command) => unit;
Shutdown a socket connection. SHUTDOWN_SEND as second argument causes reads on the other end of the connection to return an end-of-file condition. SHUTDOWN_RECEIVE causes writes on the other end of the connection to return a closed pipe condition (SIGPIPE signal).
let getsockname: file_descr => sockaddr;
Return the address of the given socket.
let getpeername: file_descr => sockaddr;
Return the address of the host connected to the given socket.
type msg_flag = 
| MSG_OOB
| MSG_DONTROUTE
| MSG_PEEK (* *)
let recv: (file_descr, bytes, int, int, list(msg_flag)) => int;
Receive data from a connected socket.
let recvfrom: (file_descr, bytes, int, int, list(msg_flag)) => (int, sockaddr);
Receive data from an unconnected socket.
let send: (file_descr, bytes, int, int, list(msg_flag)) => int;
Send data over a connected socket.
let send_substring: (file_descr, string, int, int, list(msg_flag)) => int;
Same as send, but take the data from a string instead of a byte sequence.
let sendto: (file_descr, bytes, int, int, list(msg_flag), sockaddr) => int;
Send data over an unconnected socket.
let sendto_substring: (file_descr, string, int, int, list(msg_flag), sockaddr) => int;
Same as sendto, but take the data from a string instead of a byte sequence.

Socket options

type socket_bool_option = 
| SO_DEBUG (*
Record debugging information
*)
| SO_BROADCAST (*
Permit sending of broadcast messages
*)
| SO_REUSEADDR (*
Allow reuse of local addresses for bind
*)
| SO_KEEPALIVE (*
Keep connection active
*)
| SO_DONTROUTE (*
Bypass the standard routing algorithms
*)
| SO_OOBINLINE (*
Leave out-of-band data in line
*)
| SO_ACCEPTCONN (*
Report whether socket listening is enabled
*)
| TCP_NODELAY (*
Control the Nagle algorithm for TCP sockets
*)
| IPV6_ONLY (*
Forbid binding an IPv6 socket to an IPv4 address
*)
The socket options that can be consulted with Unix.getsockopt and modified with Unix.setsockopt. These options have a boolean (true/false) value.
type socket_int_option = 
| SO_SNDBUF (*
Size of send buffer
*)
| SO_RCVBUF (*
Size of received buffer
*)
| SO_ERROR (*
Deprecated. Use Unix.getsockopt_error instead.
*)
| SO_TYPE (*
Report the socket type
*)
| SO_RCVLOWAT (*
Minimum number of bytes to process for input operations
*)
| SO_SNDLOWAT (*
Minimum number of bytes to process for output operations
*)
The socket options that can be consulted with Unix.getsockopt_int and modified with Unix.setsockopt_int. These options have an integer value.
type socket_optint_option = 
| SO_LINGER (*
Whether to linger on closed connections that have data present, and for how long (in seconds)
*)
The socket options that can be consulted with Unix.getsockopt_optint and modified with Unix.setsockopt_optint. These options have a value of type int option, with None meaning ``disabled''.
type socket_float_option = 
| SO_RCVTIMEO (*
Timeout for input operations
*)
| SO_SNDTIMEO (*
Timeout for output operations
*)
The socket options that can be consulted with Unix.getsockopt_float and modified with Unix.setsockopt_float. These options have a floating-point value representing a time in seconds. The value 0 means infinite timeout.
let getsockopt: (file_descr, socket_bool_option) => bool;
Return the current status of a boolean-valued option in the given socket.
let setsockopt: (file_descr, socket_bool_option, bool) => unit;
Set or clear a boolean-valued option in the given socket.
let getsockopt_int: (file_descr, socket_int_option) => int;
Same as Unix.getsockopt for an integer-valued socket option.
let setsockopt_int: (file_descr, socket_int_option, int) => unit;
Same as Unix.setsockopt for an integer-valued socket option.
let getsockopt_optint: (file_descr, socket_optint_option) => option(int);
Same as Unix.getsockopt for a socket option whose value is an int option.
let setsockopt_optint: (file_descr, socket_optint_option, option(int)) => unit;
Same as Unix.setsockopt for a socket option whose value is an int option.
let getsockopt_float: (file_descr, socket_float_option) => float;
Same as Unix.getsockopt for a socket option whose value is a floating-point number.
let setsockopt_float: (file_descr, socket_float_option, float) => unit;
Same as Unix.setsockopt for a socket option whose value is a floating-point number.
let getsockopt_error: file_descr => option(error);
Return the error condition associated with the given socket, and clear it.

High-level network connection functions

let open_connection: sockaddr => (Pervasives.in_channel, Pervasives.out_channel);
Connect to a server at the given address. Return a pair of buffered channels connected to the server. Remember to call Pervasives.flush on the output channel at the right times to ensure correct synchronization.
let shutdown_connection: Pervasives.in_channel => unit;
``Shut down'' a connection established with Unix.open_connection; that is, transmit an end-of-file condition to the server reading on the other side of the connection. This does not fully close the file descriptor associated with the channel, which you must remember to free via Pervasives.close_in.
let establish_server: ((Pervasives.in_channel, Pervasives.out_channel) => unit, sockaddr) => unit;
Establish a server on the given address. The function given as first argument is called for each connection with two buffered channels connected to the client. A new process is created for each connection. The function Unix.establish_server never returns normally.

Host and protocol databases

type host_entry = {
   h_name : string;
   h_aliases : string array;
   h_addrtype : socket_domain;
   h_addr_list : inet_addr array;
}
Structure of entries in the hosts database.
type protocol_entry = {
   p_name : string;
   p_aliases : string array;
   p_proto : int;
}
Structure of entries in the protocols database.
type service_entry = {
   s_name : string;
   s_aliases : string array;
   s_port : int;
   s_proto : string;
}
Structure of entries in the services database.
let gethostname: unit => string;
Return the name of the local host.
let gethostbyname: string => host_entry;
Find an entry in hosts with the given name, or raise Not_found.
let gethostbyaddr: inet_addr => host_entry;
Find an entry in hosts with the given address, or raise Not_found.
let getprotobyname: string => protocol_entry;
Find an entry in protocols with the given name, or raise Not_found.
let getprotobynumber: int => protocol_entry;
Find an entry in protocols with the given protocol number, or raise Not_found.
let getservbyname: (string, string) => service_entry;
Find an entry in services with the given name, or raise Not_found.
let getservbyport: (int, string) => service_entry;
Find an entry in services with the given service number, or raise Not_found.
type addr_info = {
   ai_family : socket_domain; (*
Socket domain
*)
   ai_socktype : socket_type; (*
Socket type
*)
   ai_protocol : int; (*
Socket protocol number
*)
   ai_addr : sockaddr; (*
Address
*)
   ai_canonname : string; (*
Canonical host name
*)
}
Address information returned by Unix.getaddrinfo.
type getaddrinfo_option = 
| AI_FAMILY of socket_domain (*
Impose the given socket domain
*)
| AI_SOCKTYPE of socket_type (*
Impose the given socket type
*)
| AI_PROTOCOL of int (*
Impose the given protocol
*)
| AI_NUMERICHOST (*
Do not call name resolver, expect numeric IP address
*)
| AI_CANONNAME (*
Fill the ai_canonname field of the result
*)
| AI_PASSIVE (*
Set address to ``any'' address for use with Unix.bind
*)
Options to Unix.getaddrinfo.
let getaddrinfo: (string, string, list(getaddrinfo_option)) => list(addr_info);
getaddrinfo host service opts returns a list of Unix.addr_info records describing socket parameters and addresses suitable for communicating with the given host and service. The empty list is returned if the host or service names are unknown, or the constraints expressed in opts cannot be satisfied.

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

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

Host and service information returned by Unix.getnameinfo.
type getnameinfo_option = 
| NI_NOFQDN (*
Do not qualify local host names
*)
| NI_NUMERICHOST (*
Always return host as IP address
*)
| NI_NAMEREQD (*
Fail if host name cannot be determined
*)
| NI_NUMERICSERV (*
Always return service as port number
*)
| NI_DGRAM (*
Consider the service as UDP-based instead of the default TCP
*)
Options to Unix.getnameinfo.
let getnameinfo: (sockaddr, list(getnameinfo_option)) => name_info;
getnameinfo addr opts returns the host name and service name corresponding to the socket address addr. opts is a possibly empty list of options that governs how these names are obtained. Raise Not_found if an error occurs.

Terminal interface


Terminal interface


The following functions implement the POSIX standard terminal interface. They provide control over asynchronous communication ports and pseudo-terminals. Refer to the termios man page for a complete description.
type terminal_io = {
   mutable c_ignbrk : bool; (*
Ignore the break condition.
*)
   mutable c_brkint : bool; (*
Signal interrupt on break condition.
*)
   mutable c_ignpar : bool; (*
Ignore characters with parity errors.
*)
   mutable c_parmrk : bool; (*
Mark parity errors.
*)
   mutable c_inpck : bool; (*
Enable parity check on input.
*)
   mutable c_istrip : bool; (*
Strip 8th bit on input characters.
*)
   mutable c_inlcr : bool; (*
Map NL to CR on input.
*)
   mutable c_igncr : bool; (*
Ignore CR on input.
*)
   mutable c_icrnl : bool; (*
Map CR to NL on input.
*)
   mutable c_ixon : bool; (*
Recognize XON/XOFF characters on input.
*)
   mutable c_ixoff : bool; (*
Emit XON/XOFF chars to control input flow.
*)
   mutable c_opost : bool; (*
Enable output processing.
*)
   mutable c_obaud : int; (*
Output baud rate (0 means close connection).
*)
   mutable c_ibaud : int; (*
Input baud rate.
*)
   mutable c_csize : int; (*
Number of bits per character (5-8).
*)
   mutable c_cstopb : int; (*
Number of stop bits (1-2).
*)
   mutable c_cread : bool; (*
Reception is enabled.
*)
   mutable c_parenb : bool; (*
Enable parity generation and detection.
*)
   mutable c_parodd : bool; (*
Specify odd parity instead of even.
*)
   mutable c_hupcl : bool; (*
Hang up on last close.
*)
   mutable c_clocal : bool; (*
Ignore modem status lines.
*)
   mutable c_isig : bool; (*
Generate signal on INTR, QUIT, SUSP.
*)
   mutable c_icanon : bool; (*
Enable canonical processing (line buffering and editing)
*)
   mutable c_noflsh : bool; (*
Disable flush after INTR, QUIT, SUSP.
*)
   mutable c_echo : bool; (*
Echo input characters.
*)
   mutable c_echoe : bool; (*
Echo ERASE (to erase previous character).
*)
   mutable c_echok : bool; (*
Echo KILL (to erase the current line).
*)
   mutable c_echonl : bool; (*
Echo NL even if c_echo is not set.
*)
   mutable c_vintr : char; (*
Interrupt character (usually ctrl-C).
*)
   mutable c_vquit : char; (*
Quit character (usually ctrl-\).
*)
   mutable c_verase : char; (*
Erase character (usually DEL or ctrl-H).
*)
   mutable c_vkill : char; (*
Kill line character (usually ctrl-U).
*)
   mutable c_veof : char; (*
End-of-file character (usually ctrl-D).
*)
   mutable c_veol : char; (*
Alternate end-of-line char. (usually none).
*)
   mutable c_vmin : int; (*
Minimum number of characters to read before the read request is satisfied.
*)
   mutable c_vtime : int; (*
Maximum read wait (in 0.1s units).
*)
   mutable c_vstart : char; (*
Start character (usually ctrl-Q).
*)
   mutable c_vstop : char; (*
Stop character (usually ctrl-S).
*)
}
let tcgetattr: file_descr => terminal_io;
Return the status of the terminal referred to by the given file descriptor.
type setattr_when = 
| TCSANOW
| TCSADRAIN
| TCSAFLUSH
let tcsetattr: (file_descr, setattr_when, terminal_io) => unit;
Set the status of the terminal referred to by the given file descriptor. The second argument indicates when the status change takes place: immediately (TCSANOW), when all pending output has been transmitted (TCSADRAIN), or after flushing all input that has been received but not read (TCSAFLUSH). TCSADRAIN is recommended when changing the output parameters; TCSAFLUSH, when changing the input parameters.
let tcsendbreak: (file_descr, int) => unit;
Send a break condition on the given file descriptor. The second argument is the duration of the break, in 0.1s units; 0 means standard duration (0.25s).
let tcdrain: file_descr => unit;
Waits until all output written on the given file descriptor has been transmitted.
type flush_queue = 
| TCIFLUSH
| TCOFLUSH
| TCIOFLUSH
let tcflush: (file_descr, flush_queue) => unit;
Discard data written on the given file descriptor but not yet transmitted, or data received but not yet read, depending on the second argument: TCIFLUSH flushes data received but not read, TCOFLUSH flushes data written but not transmitted, and TCIOFLUSH flushes both.
type flow_action = 
| TCOOFF
| TCOON
| TCIOFF
| TCION
let tcflow: (file_descr, flow_action) => unit;
Suspend or restart reception or transmission of data on the given file descriptor, depending on the second argument: TCOOFF suspends output, TCOON restarts output, TCIOFF transmits a STOP character to suspend input, and TCION transmits a START character to restart input.
let setsid: unit => int;
Put the calling process in a new session and detach it from its controlling terminal.