Size: 4

Alignment: 4

Non-negative file size or length of a region within a file.

Size: 8

Alignment: 8

Timestamp in nanoseconds.

Size: 8

Alignment: 8

Identifiers for clocks.

Size: 4

Alignment: 4

• realtime The clock measuring real time. Time value zero corresponds with 1970-01-01T00:00:00Z.

• monotonic The store-wide monotonic clock, which is defined as a clock measuring real time, whose value cannot be adjusted and which cannot have negative clock jumps. The epoch of this clock is undefined. The absolute time value of this clock therefore has no meaning.

• process_cputime_id The CPU-time clock associated with the current process.

• thread_cputime_id The CPU-time clock associated with the current thread.

Error codes returned by functions. Not all of these error codes are returned by the functions provided by this API; some are used in higher-level library layers, and others are provided merely for alignment with POSIX.

Size: 2

Alignment: 2

• success No error occurred. System call completed successfully.

• 2big Argument list too long.

• acces Permission denied.

• addrinuse Address in use.

• addrnotavail Address not available.

• afnosupport Address family not supported.

• again Resource unavailable, or operation would block.

• already Connection already in progress.

• badf Bad file descriptor.

• badmsg Bad message.

• busy Device or resource busy.

• canceled Operation canceled.

• child No child processes.

• connaborted Connection aborted.

• connrefused Connection refused.

• connreset Connection reset.

• deadlk Resource deadlock would occur.

• destaddrreq Destination address required.

• dom Mathematics argument out of domain of function.

• dquot Reserved.

• exist File exists.

• fault Bad address.

• fbig File too large.

• hostunreach Host is unreachable.

• idrm Identifier removed.

• ilseq Illegal byte sequence.

• inprogress Operation in progress.

• intr Interrupted function.

• inval Invalid argument.

• io I/O error.

• isconn Socket is connected.

• isdir Is a directory.

• loop Too many levels of symbolic links.

• mfile File descriptor value too large.

• mlink Too many links.

• msgsize Message too large.

• multihop Reserved.

• nametoolong Filename too long.

• netdown Network is down.

• netreset Connection aborted by network.

• netunreach Network unreachable.

• nfile Too many files open in system.

• nobufs No buffer space available.

• nodev No such device.

• noent No such file or directory.

• noexec Executable file format error.

• nolck No locks available.

• nolink Reserved.

• nomem Not enough space.

• nomsg No message of the desired type.

• noprotoopt Protocol not available.

• nospc No space left on device.

• nosys Function not supported.

• notconn The socket is not connected.

• notdir Not a directory or a symbolic link to a directory.

• notempty Directory not empty.

• notrecoverable State not recoverable.

• notsock Not a socket.

• notsup Not supported, or operation not supported on socket.

• notty Inappropriate I/O control operation.

• nxio No such device or address.

• overflow Value too large to be stored in data type.

• ownerdead Previous owner died.

• perm Operation not permitted.

• pipe Broken pipe.

• proto Protocol error.

• protonosupport Protocol not supported.

• prototype Protocol wrong type for socket.

• range Result too large.

• rofs Read-only file system.

• spipe Invalid seek.

• srch No such process.

• stale Reserved.

• timedout Connection timed out.

• txtbsy Text file busy.

• xdev Cross-device link.

• notcapable Extension: Capabilities insufficient.

File descriptor rights, determining which actions may be performed.

Size: 8

Alignment: 8

• fd_datasync: bool The right to invoke fd_datasync. If path_open is set, includes the right to invoke path_open with fdflags::dsync.

Bit: 0

• fd_read: bool The right to invoke fd_read and sock_recv. If rights::fd_seek is set, includes the right to invoke fd_pread.

Bit: 1

• fd_seek: bool The right to invoke fd_seek. This flag implies rights::fd_tell.

Bit: 2

• fd_fdstat_set_flags: bool The right to invoke fd_fdstat_set_flags.

Bit: 3

• fd_sync: bool The right to invoke fd_sync. If path_open is set, includes the right to invoke path_open with fdflags::rsync and fdflags::dsync.

Bit: 4

• fd_tell: bool The right to invoke fd_seek in such a way that the file offset remains unaltered (i.e., whence::cur with offset zero), or to invoke fd_tell.

Bit: 5

• fd_write: bool The right to invoke fd_write and sock_send. If rights::fd_seek is set, includes the right to invoke fd_pwrite.

Bit: 6

• fd_advise: bool The right to invoke fd_advise.

Bit: 7

• fd_allocate: bool The right to invoke fd_allocate.

Bit: 8

• path_create_directory: bool The right to invoke path_create_directory.

Bit: 9

• path_create_file: bool If path_open is set, the right to invoke path_open with oflags::creat.

Bit: 10

• path_link_source: bool The right to invoke path_link with the file descriptor as the source directory.

Bit: 11

• path_link_target: bool The right to invoke path_link with the file descriptor as the target directory.

Bit: 12

• path_open: bool The right to invoke path_open.

Bit: 13

• fd_readdir: bool The right to invoke fd_readdir.

Bit: 14

• path_readlink: bool The right to invoke path_readlink.

Bit: 15

• path_rename_source: bool The right to invoke path_rename with the file descriptor as the source directory.

Bit: 16

• path_rename_target: bool The right to invoke path_rename with the file descriptor as the target directory.

Bit: 17

• path_filestat_get: bool The right to invoke path_filestat_get.

Bit: 18

• path_filestat_set_size: bool The right to change a file's size. If path_open is set, includes the right to invoke path_open with oflags::trunc. Note: there is no function named path_filestat_set_size. This follows POSIX design, which only has ftruncate and does not provide ftruncateat. While such function would be desirable from the API design perspective, there are virtually no use cases for it since no code written for POSIX systems would use it. Moreover, implementing it would require multiple syscalls, leading to inferior performance.

Bit: 19

• path_filestat_set_times: bool The right to invoke path_filestat_set_times.

Bit: 20

• fd_filestat_get: bool The right to invoke fd_filestat_get.

Bit: 21

• fd_filestat_set_size: bool The right to invoke fd_filestat_set_size.

Bit: 22

• fd_filestat_set_times: bool The right to invoke fd_filestat_set_times.

Bit: 23

• path_symlink: bool The right to invoke path_symlink.

Bit: 24

• path_remove_directory: bool The right to invoke path_remove_directory.

Bit: 25

• path_unlink_file: bool The right to invoke path_unlink_file.

Bit: 26

• poll_fd_readwrite: bool If rights::fd_read is set, includes the right to invoke poll_oneoff to subscribe to eventtype::fd_read. If rights::fd_write is set, includes the right to invoke poll_oneoff to subscribe to eventtype::fd_write.

Bit: 27

• sock_shutdown: bool The right to invoke sock_shutdown.

Bit: 28

• sock_accept: bool The right to invoke sock_accept.

Bit: 29

A file descriptor handle.

Size: 4

Alignment: 4

A region of memory for scatter/gather reads.

Size: 8

Alignment: 4

• buf: Pointer<u8> The address of the buffer to be filled.

Offset: 0

• buf_len: size The length of the buffer to be filled.

Offset: 4

A region of memory for scatter/gather writes.

Size: 8

Alignment: 4

• buf: ConstPointer<u8> The address of the buffer to be written.

Offset: 0

• buf_len: size The length of the buffer to be written.

Offset: 4

Size: 8

Alignment: 4

Size: 8

Alignment: 4

Relative offset within a file.

Size: 8

Alignment: 8

The position relative to which to set the offset of the file descriptor.

Size: 1

Alignment: 1

• set Seek relative to start-of-file.

• cur Seek relative to current position.

• end Seek relative to end-of-file.

A reference to the offset of a directory entry.

The value 0 signifies the start of the directory.

Size: 8

Alignment: 8

The type for the dirent::d_namlen field of dirent struct.

Size: 4

Alignment: 4

File serial number that is unique within its file system.

Size: 8

Alignment: 8

The type of a file descriptor or file.

Size: 1

Alignment: 1

• unknown The type of the file descriptor or file is unknown or is different from any of the other types specified.

• block_device The file descriptor or file refers to a block device inode.

• character_device The file descriptor or file refers to a character device inode.

• directory The file descriptor or file refers to a directory inode.

• regular_file The file descriptor or file refers to a regular file inode.

• socket_dgram The file descriptor or file refers to a datagram socket.

• socket_stream The file descriptor or file refers to a byte-stream socket.

• symbolic_link The file refers to a symbolic link inode.

A directory entry.

Size: 24

Alignment: 8

• d_next: dircookie The offset of the next directory entry stored in this directory.

Offset: 0

• d_ino: inode The serial number of the file referred to by this directory entry.

Offset: 8

• d_namlen: dirnamlen The length of the name of the directory entry.

Offset: 16

• d_type: filetype The type of the file referred to by this directory entry.

Offset: 20

File or memory access pattern advisory information.

Size: 1

Alignment: 1

• normal The application has no advice to give on its behavior with respect to the specified data.

• sequential The application expects to access the specified data sequentially from lower offsets to higher offsets.

• random The application expects to access the specified data in a random order.

• willneed The application expects to access the specified data in the near future.

• dontneed The application expects that it will not access the specified data in the near future.

• noreuse The application expects to access the specified data once and then not reuse it thereafter.

File descriptor flags.

Size: 2

Alignment: 2

• append: bool Append mode: Data written to the file is always appended to the file's end.

Bit: 0

• dsync: bool Write according to synchronized I/O data integrity completion. Only the data stored in the file is synchronized.

Bit: 1

• nonblock: bool Non-blocking mode.

Bit: 2

• rsync: bool Synchronized read I/O operations.

Bit: 3

• sync: bool Write according to synchronized I/O file integrity completion. In addition to synchronizing the data stored in the file, the implementation may also synchronously update the file's metadata.

Bit: 4

File descriptor attributes.

Size: 24

Alignment: 8

• fs_filetype: filetype File type.

Offset: 0

• fs_flags: fdflags File descriptor flags.

Offset: 2

• fs_rights_base: rights Rights that apply to this file descriptor.

Offset: 8

• fs_rights_inheriting: rights Maximum set of rights that may be installed on new file descriptors that are created through this file descriptor, e.g., through path_open.

Offset: 16

Identifier for a device containing a file system. Can be used in combination with inode to uniquely identify a file or directory in the filesystem.

Size: 8

Alignment: 8

Which file time attributes to adjust.

Size: 2

Alignment: 2

• atim: bool Adjust the last data access timestamp to the value stored in filestat::atim.

Bit: 0

• atim_now: bool Adjust the last data access timestamp to the time of clock clockid::realtime.

Bit: 1

• mtim: bool Adjust the last data modification timestamp to the value stored in filestat::mtim.

Bit: 2

• mtim_now: bool Adjust the last data modification timestamp to the time of clock clockid::realtime.

Bit: 3

Flags determining the method of how paths are resolved.

Size: 4

Alignment: 4

• symlink_follow: bool As long as the resolved path corresponds to a symbolic link, it is expanded.

Bit: 0

Open flags used by path_open.

Size: 2

Alignment: 2

• creat: bool Create file if it does not exist.

Bit: 0

• directory: bool Fail if not a directory.

Bit: 1

• excl: bool Fail if file already exists.

Bit: 2

• trunc: bool Truncate file to size 0.

Bit: 3

Number of hard links to an inode.

Size: 8

Alignment: 8

File attributes.

Size: 64

Alignment: 8

• dev: device Device ID of device containing the file.

Offset: 0

• ino: inode File serial number.

Offset: 8

• filetype: filetype File type.

Offset: 16

• nlink: linkcount Number of hard links to the file.

Offset: 24

• size: filesize For regular files, the file size in bytes. For symbolic links, the length in bytes of the pathname contained in the symbolic link.

Offset: 32

• atim: timestamp Last data access timestamp.

Offset: 40

• mtim: timestamp Last data modification timestamp.

Offset: 48

• ctim: timestamp Last file status change timestamp.

Offset: 56

User-provided value that may be attached to objects that is retained when extracted from the implementation.

Size: 8

Alignment: 8

Type of a subscription to an event or its occurrence.

Size: 1

Alignment: 1

• clock The time value of clock subscription_clock::id has reached timestamp subscription_clock::timeout.

• fd_read File descriptor subscription_fd_readwrite::file_descriptor has data available for reading. This event always triggers for regular files.

• fd_write File descriptor subscription_fd_readwrite::file_descriptor has capacity available for writing. This event always triggers for regular files.

The state of the file descriptor subscribed to with eventtype::fd_read or eventtype::fd_write.

Size: 2

Alignment: 2

• fd_readwrite_hangup: bool The peer of this socket has closed or disconnected.

Bit: 0

The contents of an event when type is eventtype::fd_read or eventtype::fd_write.

Size: 16

Alignment: 8

• nbytes: filesize The number of bytes available for reading or writing.

Offset: 0

• flags: eventrwflags The state of the file descriptor.

Offset: 8

An event that occurred.

Size: 32

Alignment: 8

• userdata: userdata User-provided value that got attached to subscription::userdata.

Offset: 0

• error: errno If non-zero, an error that occurred while processing the subscription request.

Offset: 8

• type: eventtype The type of event that occured

Offset: 10

• fd_readwrite: event_fd_readwrite The contents of the event, if it is an eventtype::fd_read or eventtype::fd_write. eventtype::clock events ignore this field.

Offset: 16

Flags determining how to interpret the timestamp provided in subscription_clock::timeout.

Size: 2

Alignment: 2

• subscription_clock_abstime: bool If set, treat the timestamp provided in subscription_clock::timeout as an absolute timestamp of clock subscription_clock::id. If clear, treat the timestamp provided in subscription_clock::timeout relative to the current time value of clock subscription_clock::id.

Bit: 0

The contents of a subscription when type is eventtype::clock.

Size: 32

Alignment: 8

• id: clockid The clock against which to compare the timestamp.

Offset: 0

• timeout: timestamp The absolute or relative timestamp.

Offset: 8

• precision: timestamp The amount of time that the implementation may wait additionally to coalesce with other events.

Offset: 16

• flags: subclockflags Flags specifying whether the timeout is absolute or relative

Offset: 24

The contents of a subscription when type is type is eventtype::fd_read or eventtype::fd_write.

Size: 4

Alignment: 4

• file_descriptor: fd The file descriptor on which to wait for it to become ready for reading or writing.

Offset: 0

The contents of a subscription.

Size: 40

Alignment: 8

• size: 40
• align: 8
• tag_size: 1

• clock: subscription_clock

• fd_read: subscription_fd_readwrite

• fd_write: subscription_fd_readwrite

Subscription to an event.

Size: 48

Alignment: 8

• userdata: userdata User-provided value that is attached to the subscription in the implementation and returned through event::userdata.

Offset: 0

• u: subscription_u The type of the event to which to subscribe, and its contents

Offset: 8

Exit code generated by a process when exiting.

Size: 4

Alignment: 4

Signal condition.

Size: 1

Alignment: 1

• none No signal. Note that POSIX has special semantics for kill(pid, 0), so this value is reserved.

• hup Hangup. Action: Terminates the process.

• int Terminate interrupt signal. Action: Terminates the process.

• quit Terminal quit signal. Action: Terminates the process.

• ill Illegal instruction. Action: Terminates the process.

• trap Trace/breakpoint trap. Action: Terminates the process.

• abrt Process abort signal. Action: Terminates the process.

• bus Access to an undefined portion of a memory object. Action: Terminates the process.

• fpe Erroneous arithmetic operation. Action: Terminates the process.

• kill Kill. Action: Terminates the process.

• usr1 User-defined signal 1. Action: Terminates the process.

• segv Invalid memory reference. Action: Terminates the process.

• usr2 User-defined signal 2. Action: Terminates the process.

• pipe Write on a pipe with no one to read it. Action: Ignored.

• alrm Alarm clock. Action: Terminates the process.

• term Termination signal. Action: Terminates the process.

• chld Child process terminated, stopped, or continued. Action: Ignored.

• cont Continue executing, if stopped. Action: Continues executing, if stopped.

• stop Stop executing. Action: Stops executing.

• tstp Terminal stop signal. Action: Stops executing.

• ttin Background process attempting read. Action: Stops executing.

• ttou Background process attempting write. Action: Stops executing.

• urg High bandwidth data is available at a socket. Action: Ignored.

• xcpu CPU time limit exceeded. Action: Terminates the process.

• xfsz File size limit exceeded. Action: Terminates the process.

• vtalrm Virtual timer expired. Action: Terminates the process.

• prof Profiling timer expired. Action: Terminates the process.

• winch Window changed. Action: Ignored.

• poll I/O possible. Action: Terminates the process.

• pwr Power failure. Action: Terminates the process.

• sys Bad system call. Action: Terminates the process.

Flags provided to sock_recv.

Size: 2

Alignment: 2

• recv_peek: bool Returns the message without removing it from the socket's receive queue.

Bit: 0

• recv_waitall: bool On byte-stream sockets, block until the full amount of data can be returned.

Bit: 1

Flags returned by sock_recv.

Size: 2

Alignment: 2

• recv_data_truncated: bool Returned by sock_recv: Message data has been truncated.

Bit: 0

Flags provided to sock_send. As there are currently no flags defined, it must be set to zero.

Size: 2

Alignment: 2

Which channels on a socket to shut down.

Size: 1

Alignment: 1

• rd: bool Disables further receive operations.

Bit: 0

• wr: bool Disables further send operations.

Bit: 1

Identifiers for preopened capabilities.

Size: 1

Alignment: 1

• dir A pre-opened directory.

The contents of a $prestat when type is preopentype::dir.

Size: 4

Alignment: 4

• pr_name_len: size The length of the directory name for use with fd_prestat_dir_name.

Offset: 0

Information about a pre-opened capability.

Size: 8

Alignment: 4

• size: 8
• align: 4
• tag_size: 1

• dir: prestat_dir

Read command-line argument data. The size of the array should match that returned by args_sizes_get. Each argument is expected to be \0 terminated.

• argv: Pointer<Pointer<u8>>

• argv_buf: Pointer<u8>

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Return command-line argument data sizes.

• error: Result<(size, size), errno> Returns the number of arguments and the size of the argument string data, or an error.

• size: 12
• align: 4
• tag_size: 4

• ok: (size, size)

####### Record members

• 0: size

Offset: 0

• 1: size

Offset: 4

• err: errno

Read environment variable data. The sizes of the buffers should match that returned by environ_sizes_get. Key/value pairs are expected to be joined with =s, and terminated with \0s.

• environ: Pointer<Pointer<u8>>

• environ_buf: Pointer<u8>

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Return environment variable data sizes.

• error: Result<(size, size), errno> Returns the number of environment variable arguments and the size of the environment variable data.

• size: 12
• align: 4
• tag_size: 4

• ok: (size, size)

####### Record members

• 0: size

Offset: 0

• 1: size

Offset: 4

• err: errno

Return the resolution of a clock. Implementations are required to provide a non-zero value for supported clocks. For unsupported clocks, return errno::inval. Note: This is similar to clock_getres in POSIX.

• id: clockid The clock for which to return the resolution.

• error: Result<timestamp, errno> The resolution of the clock, or an error if one happened.

• size: 16
• align: 8
• tag_size: 4

• ok: timestamp

• err: errno

Return the time value of a clock. Note: This is similar to clock_gettime in POSIX.

• id: clockid The clock for which to return the time.

• precision: timestamp The maximum lag (exclusive) that the returned time value may have, compared to its actual value.

• error: Result<timestamp, errno> The time value of the clock.

• size: 16
• align: 8
• tag_size: 4

• ok: timestamp

• err: errno

Provide file advisory information on a file descriptor. Note: This is similar to posix_fadvise in POSIX.

• fd: fd

• offset: filesize The offset within the file to which the advisory applies.

• len: filesize The length of the region to which the advisory applies.

• advice: advice The advice.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Force the allocation of space in a file. Note: This is similar to posix_fallocate in POSIX.

• fd: fd

• offset: filesize The offset at which to start the allocation.

• len: filesize The length of the area that is allocated.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Close a file descriptor. Note: This is similar to close in POSIX.

• fd: fd

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Synchronize the data of a file to disk. Note: This is similar to fdatasync in POSIX.

• fd: fd

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Get the attributes of a file descriptor. Note: This returns similar flags to fcntl(fd, F_GETFL) in POSIX, as well as additional fields.

• fd: fd

• error: Result<fdstat, errno> The buffer where the file descriptor's attributes are stored.

• size: 32
• align: 8
• tag_size: 4

• ok: fdstat

• err: errno

Adjust the flags associated with a file descriptor. Note: This is similar to fcntl(fd, F_SETFL, flags) in POSIX.

• fd: fd

• flags: fdflags The desired values of the file descriptor flags.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Adjust the rights associated with a file descriptor. This can only be used to remove rights, and returns errno::notcapable if called in a way that would attempt to add rights

• fd: fd

• fs_rights_base: rights The desired rights of the file descriptor.

• fs_rights_inheriting: rights

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Return the attributes of an open file.

• fd: fd

• error: Result<filestat, errno> The buffer where the file's attributes are stored.

• size: 72
• align: 8
• tag_size: 4

• ok: filestat

• err: errno

Adjust the size of an open file. If this increases the file's size, the extra bytes are filled with zeros. Note: This is similar to ftruncate in POSIX.

• fd: fd

• size: filesize The desired file size.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Adjust the timestamps of an open file or directory. Note: This is similar to futimens in POSIX.

• fd: fd

• atim: timestamp The desired values of the data access timestamp.

• mtim: timestamp The desired values of the data modification timestamp.

• fst_flags: fstflags A bitmask indicating which timestamps to adjust.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Read from a file descriptor, without using and updating the file descriptor's offset. Note: This is similar to preadv in Linux (and other Unix-es).

• fd: fd

• iovs: iovec_array List of scatter/gather vectors in which to store data.

• offset: filesize The offset within the file at which to read.

• error: Result<size, errno> The number of bytes read.

• size: 8
• align: 4
• tag_size: 4

• ok: size

• err: errno

Return a description of the given preopened file descriptor.

• fd: fd

• error: Result<prestat, errno> The buffer where the description is stored.

• size: 12
• align: 4
• tag_size: 4

• ok: prestat

• err: errno

Return a description of the given preopened file descriptor.

• fd: fd

• path: Pointer<u8> A buffer into which to write the preopened directory name.

• path_len: size

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Write to a file descriptor, without using and updating the file descriptor's offset. Note: This is similar to pwritev in Linux (and other Unix-es).

Like Linux (and other Unix-es), any calls of pwrite (and other functions to read or write) for a regular file by other threads in the WASI process should not be interleaved while pwrite is executed.

• fd: fd

• iovs: ciovec_array List of scatter/gather vectors from which to retrieve data.

• offset: filesize The offset within the file at which to write.

• error: Result<size, errno> The number of bytes written.

• size: 8
• align: 4
• tag_size: 4

• ok: size

• err: errno

Read from a file descriptor. Note: This is similar to readv in POSIX.

• fd: fd

• iovs: iovec_array List of scatter/gather vectors to which to store data.

• error: Result<size, errno> The number of bytes read.

• size: 8
• align: 4
• tag_size: 4

• ok: size

• err: errno

Read directory entries from a directory. When successful, the contents of the output buffer consist of a sequence of directory entries. Each directory entry consists of a dirent object, followed by dirent::d_namlen bytes holding the name of the directory entry. This function fills the output buffer as much as possible, potentially truncating the last directory entry. This allows the caller to grow its read buffer size in case it's too small to fit a single large directory entry, or skip the oversized directory entry.

• fd: fd

• buf: Pointer<u8> The buffer where directory entries are stored

• buf_len: size

• cookie: dircookie The location within the directory to start reading

• error: Result<size, errno> The number of bytes stored in the read buffer. If less than the size of the read buffer, the end of the directory has been reached.

• size: 8
• align: 4
• tag_size: 4

• ok: size

• err: errno

Atomically replace a file descriptor by renumbering another file descriptor. Due to the strong focus on thread safety, this environment does not provide a mechanism to duplicate or renumber a file descriptor to an arbitrary number, like dup2(). This would be prone to race conditions, as an actual file descriptor with the same number could be allocated by a different thread at the same time. This function provides a way to atomically renumber file descriptors, which would disappear if dup2() were to be removed entirely.

• fd: fd

• to: fd The file descriptor to overwrite.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Move the offset of a file descriptor. Note: This is similar to lseek in POSIX.

• fd: fd

• offset: filedelta The number of bytes to move.

• whence: whence The base from which the offset is relative.

• error: Result<filesize, errno> The new offset of the file descriptor, relative to the start of the file.

• size: 16
• align: 8
• tag_size: 4

• ok: filesize

• err: errno

Synchronize the data and metadata of a file to disk. Note: This is similar to fsync in POSIX.

• fd: fd

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Return the current offset of a file descriptor. Note: This is similar to lseek(fd, 0, SEEK_CUR) in POSIX.

• fd: fd

• error: Result<filesize, errno> The current offset of the file descriptor, relative to the start of the file.

• size: 16
• align: 8
• tag_size: 4

• ok: filesize

• err: errno

Write to a file descriptor. Note: This is similar to writev in POSIX.

Like POSIX, any calls of write (and other functions to read or write) for a regular file by other threads in the WASI process should not be interleaved while write is executed.

• fd: fd

• iovs: ciovec_array List of scatter/gather vectors from which to retrieve data.

• error: Result<size, errno>

• size: 8
• align: 4
• tag_size: 4

• ok: size

• err: errno

Create a directory. Note: This is similar to mkdirat in POSIX.

• fd: fd

• path: string The path at which to create the directory.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Return the attributes of a file or directory. Note: This is similar to stat in POSIX.

• fd: fd

• flags: lookupflags Flags determining the method of how the path is resolved.

• path: string The path of the file or directory to inspect.

• error: Result<filestat, errno> The buffer where the file's attributes are stored.

• size: 72
• align: 8
• tag_size: 4

• ok: filestat

• err: errno

Adjust the timestamps of a file or directory. Note: This is similar to utimensat in POSIX.

• fd: fd

• flags: lookupflags Flags determining the method of how the path is resolved.

• path: string The path of the file or directory to operate on.

• atim: timestamp The desired values of the data access timestamp.

• mtim: timestamp The desired values of the data modification timestamp.

• fst_flags: fstflags A bitmask indicating which timestamps to adjust.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Create a hard link. Note: This is similar to linkat in POSIX.

• old_fd: fd

• old_flags: lookupflags Flags determining the method of how the path is resolved.

• old_path: string The source path from which to link.

• new_fd: fd The working directory at which the resolution of the new path starts.

• new_path: string The destination path at which to create the hard link.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Open a file or directory. The returned file descriptor is not guaranteed to be the lowest-numbered file descriptor not currently open; it is randomized to prevent applications from depending on making assumptions about indexes, since this is error-prone in multi-threaded contexts. The returned file descriptor is guaranteed to be less than 2**31. Note: This is similar to openat in POSIX.

• fd: fd

• dirflags: lookupflags Flags determining the method of how the path is resolved.

• path: string The relative path of the file or directory to open, relative to the path_open::fd directory.

• oflags: oflags The method by which to open the file.

• fs_rights_base: rights The initial rights of the newly created file descriptor. The implementation is allowed to return a file descriptor with fewer rights than specified, if and only if those rights do not apply to the type of file being opened. The base rights are rights that will apply to operations using the file descriptor itself, while the inheriting rights are rights that apply to file descriptors derived from it.

• fs_rights_inheriting: rights

• fdflags: fdflags

• error: Result<fd, errno> The file descriptor of the file that has been opened.

• size: 8
• align: 4
• tag_size: 4

• ok: fd

• err: errno

Read the contents of a symbolic link. Note: This is similar to readlinkat in POSIX.

• fd: fd

• path: string The path of the symbolic link from which to read.

• buf: Pointer<u8> The buffer to which to write the contents of the symbolic link.

• buf_len: size

• error: Result<size, errno> The number of bytes placed in the buffer.

• size: 8
• align: 4
• tag_size: 4

• ok: size

• err: errno

Remove a directory. Return errno::notempty if the directory is not empty. Note: This is similar to unlinkat(fd, path, AT_REMOVEDIR) in POSIX.

• fd: fd

• path: string The path to a directory to remove.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Rename a file or directory. Note: This is similar to renameat in POSIX.

• fd: fd

• old_path: string The source path of the file or directory to rename.

• new_fd: fd The working directory at which the resolution of the new path starts.

• new_path: string The destination path to which to rename the file or directory.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Create a symbolic link. Note: This is similar to symlinkat in POSIX.

• old_path: string The contents of the symbolic link.

• fd: fd

• new_path: string The destination path at which to create the symbolic link.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Unlink a file. Return errno::isdir if the path refers to a directory. Note: This is similar to unlinkat(fd, path, 0) in POSIX.

• fd: fd

• path: string The path to a file to unlink.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Concurrently poll for the occurrence of a set of events.

If nsubscriptions is 0, returns errno::inval.

• in: ConstPointer<subscription> The events to which to subscribe.

• out: Pointer<event> The events that have occurred.

• nsubscriptions: size Both the number of subscriptions and events.

• error: Result<size, errno> The number of events stored.

• size: 8
• align: 4
• tag_size: 4

• ok: size

• err: errno

Terminate the process normally. An exit code of 0 indicates successful termination of the program. The meanings of other values is dependent on the environment.

• rval: exitcode The exit code returned by the process.

Send a signal to the process of the calling thread. Note: This is similar to raise in POSIX.

• sig: signal The signal condition to trigger.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Temporarily yield execution of the calling thread. Note: This is similar to sched_yield in POSIX.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Write high-quality random data into a buffer. This function blocks when the implementation is unable to immediately provide sufficient high-quality random data. This function may execute slowly, so when large mounts of random data are required, it's advisable to use this function to seed a pseudo-random number generator, rather than to provide the random data directly.

• buf: Pointer<u8> The buffer to fill with random data.

• buf_len: size

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno

Accept a new incoming connection. Note: This is similar to accept in POSIX.

• fd: fd The listening socket.

• flags: fdflags The desired values of the file descriptor flags.

• error: Result<fd, errno> New socket connection

• size: 8
• align: 4
• tag_size: 4

• ok: fd

• err: errno

Receive a message from a socket. Note: This is similar to recv in POSIX, though it also supports reading the data into multiple buffers in the manner of readv.

• fd: fd

• ri_data: iovec_array List of scatter/gather vectors to which to store data.

• ri_flags: riflags Message flags.

• error: Result<(size, roflags), errno> Number of bytes stored in ri_data and message flags.

• size: 12
• align: 4
• tag_size: 4

• ok: (size, roflags)

####### Record members

• 0: size

Offset: 0

• 1: roflags

Offset: 4

• err: errno

Send a message on a socket. Note: This is similar to send in POSIX, though it also supports writing the data from multiple buffers in the manner of writev.

• fd: fd

• si_data: ciovec_array List of scatter/gather vectors to which to retrieve data

• si_flags: siflags Message flags.

• error: Result<size, errno> Number of bytes transmitted.

• size: 8
• align: 4
• tag_size: 4

• ok: size

• err: errno

Shut down socket send and receive channels. Note: This is similar to shutdown in POSIX.

• fd: fd

• how: sdflags Which channels on the socket to shut down.

• error: Result<(), errno>

• size: 8
• align: 4
• tag_size: 4

• ok

• err: errno