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+Input and Output Primitives Manager
+###################################
+
+Introduction
+============
+
+The input and output primitives manager is ...
+
+The directives provided by the input and output primitives manager are:
+
+- ``pipe`` - Create an Inter-Process Channel
+
+- ``dup`` - Duplicates an open file descriptor
+
+- ``dup2`` - Duplicates an open file descriptor
+
+- ``close`` - Closes a file
+
+- ``read`` - Reads from a file
+
+- ``write`` - Writes to a file
+
+- ``fcntl`` - Manipulates an open file descriptor
+
+- ``lseek`` - Reposition read/write file offset
+
+- ``fsync`` - Synchronize file complete in-core state with that on disk
+
+- ``fdatasync`` - Synchronize file in-core data with that on disk
+
+- ``sync`` - Schedule file system updates
+
+- ``mount`` - Mount a file system
+
+- ``unmount`` - Unmount file systems
+
+- ``readv`` - Vectored read from a file
+
+- ``writev`` - Vectored write to a file
+
+- ``aio_read`` - Asynchronous Read
+
+- ``aio_write`` - Asynchronous Write
+
+- ``lio_listio`` - List Directed I/O
+
+- ``aio_error`` - Retrieve Error Status of Asynchronous I/O Operation
+
+- ``aio_return`` - Retrieve Return Status Asynchronous I/O Operation
+
+- ``aio_cancel`` - Cancel Asynchronous I/O Request
+
+- ``aio_suspend`` - Wait for Asynchronous I/O Request
+
+- ``aio_fsync`` - Asynchronous File Synchronization
+
+Background
+==========
+
+There is currently no text in this section.
+
+Operations
+==========
+
+There is currently no text in this section.
+
+Directives
+==========
+
+This section details the input and output primitives manager’s directives.
+A subsection is dedicated to each of this manager’s directives
+and describes the calling sequence, related constants, usage,
+and status codes.
+
+pipe - Create an Inter-Process Channel
+--------------------------------------
+.. index:: pipe
+.. index:: create an inter
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ int pipe(
+ );
+
+**STATUS CODES:**
+
+*E*
+ The
+
+**DESCRIPTION:**
+
+**NOTES:**
+
+This routine is not currently supported by RTEMS but could be
+in a future version.
+
+dup - Duplicates an open file descriptor
+----------------------------------------
+.. index:: dup
+.. index:: duplicates an open file descriptor
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ #include <unistd.h>
+ int dup(
+ int fildes
+ );
+
+**STATUS CODES:**
+
+*EBADF*
+ Invalid file descriptor.
+
+*EINTR*
+ Function was interrupted by a signal.
+
+*EMFILE*
+ The process already has the maximum number of file descriptors open
+ and tried to open a new one.
+
+**DESCRIPTION:**
+
+The ``dup`` function returns the lowest numbered available file
+descriptor. This new desciptor refers to the same open file as the
+original descriptor and shares any locks.
+
+**NOTES:**
+
+NONE
+
+dup2 - Duplicates an open file descriptor
+-----------------------------------------
+.. index:: dup2
+.. index:: duplicates an open file descriptor
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ #include <unistd.h>
+ int dup2(
+ int fildes,
+ int fildes2
+ );
+
+**STATUS CODES:**
+
+*EBADF*
+ Invalid file descriptor.
+
+*EINTR*
+ Function was interrupted by a signal.
+
+*EMFILE*
+ The process already has the maximum number of file descriptors open
+ and tried to open a new one.
+
+**DESCRIPTION:**
+
+``dup2`` creates a copy of the file descriptor ``oldfd``.
+
+The old and new descriptors may be used interchangeably. They share locks, file
+position pointers and flags; for example, if the file position is modified by using``lseek`` on one of the descriptors, the position is also changed for the other.
+
+**NOTES:**
+
+NONE
+
+close - Closes a file
+---------------------
+.. index:: close
+.. index:: closes a file.
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ #include <unistd.h>
+ int close(
+ int fildes
+ );
+
+**STATUS CODES:**
+
+*EBADF*
+ Invalid file descriptor
+
+*EINTR*
+ Function was interrupted by a signal.
+
+**DESCRIPTION:**
+
+The ``close()`` function deallocates the file descriptor named by``fildes`` and makes it available for reuse. All outstanding
+record locks owned by this process for the file are unlocked.
+
+**NOTES:**
+
+A signal can interrupt the ``close()`` function. In that case,``close()`` returns -1 with ``errno`` set to EINTR. The file
+may or may not be closed.
+
+read - Reads from a file
+------------------------
+.. index:: read
+.. index:: reads from a file
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ #include <unistd.h>
+ int read(
+ int fildes,
+ void \*buf,
+ unsigned int nbyte
+ );
+
+**STATUS CODES:**
+
+On error, this routine returns -1 and sets ``errno`` to one of
+the following:
+
+*EAGAIN*
+ The O_NONBLOCK flag is set for a file descriptor and the process
+ would be delayed in the I/O operation.
+
+*EBADF*
+ Invalid file descriptor
+
+*EINTR*
+ Function was interrupted by a signal.
+
+*EIO*
+ Input or output error
+
+*EINVAL*
+ Bad buffer pointer
+
+**DESCRIPTION:**
+
+The ``read()`` function reads ``nbyte`` bytes from the file
+associated with ``fildes`` into the buffer pointed to by ``buf``.
+
+The ``read()`` function returns the number of bytes actually read
+and placed in the buffer. This will be less than ``nbyte`` if:
+
+- The number of bytes left in the file is less than ``nbyte``.
+
+- The ``read()`` request was interrupted by a signal.
+
+- The file is a pipe or FIFO or special file with less than ``nbytes``
+ immediately available for reading.
+
+When attempting to read from any empty pipe or FIFO:
+
+- If no process has the pipe open for writing, zero is returned to
+ indicate end-of-file.
+
+- If some process has the pipe open for writing and O_NONBLOCK is set,
+ -1 is returned and ``errno`` is set to EAGAIN.
+
+- If some process has the pipe open for writing and O_NONBLOCK is clear,``read()`` waits for some data to be written or the pipe to be closed.
+
+When attempting to read from a file other than a pipe or FIFO and no data
+is available.
+
+- If O_NONBLOCK is set, -1 is returned and ``errno`` is set to EAGAIN.
+
+- If O_NONBLOCK is clear, ``read()`` waits for some data to become
+ available.
+
+- The O_NONBLOCK flag is ignored if data is available.
+
+**NOTES:**
+
+NONE
+
+write - Writes to a file
+------------------------
+.. index:: write
+.. index:: writes to a file
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ #include <unistd.h>
+ int write(
+ int fildes,
+ const void \*buf,
+ unsigned int nbytes
+ );
+
+**STATUS CODES:**
+
+*EAGAIN*
+ The O_NONBLOCK flag is set for a file descriptor and the process
+ would be delayed in the I/O operation.
+
+*EBADF*
+ Invalid file descriptor
+
+*EFBIG*
+ An attempt was made to write to a file that exceeds the maximum file
+ size
+
+*EINTR*
+ The function was interrupted by a signal.
+
+*EIO*
+ Input or output error.
+
+*ENOSPC*
+ No space left on disk.
+
+*EPIPE*
+ Attempt to write to a pope or FIFO with no reader.
+
+*EINVAL*
+ Bad buffer pointer
+
+**DESCRIPTION:**
+
+The ``write()`` function writes ``nbyte`` from the array pointed
+to by ``buf`` into the file associated with ``fildes``.
+
+If ``nybte`` is zero and the file is a regular file, the ``write()``
+function returns zero and has no other effect. If ``nbyte`` is zero
+and the file is a special file, te results are not portable.
+
+The ``write()`` function returns the number of bytes written. This
+number will be less than ``nbytes`` if there is an error. It will never
+be greater than ``nbytes``.
+
+**NOTES:**
+
+NONE
+
+fcntl - Manipulates an open file descriptor
+-------------------------------------------
+.. index:: fcntl
+.. index:: manipulates an open file descriptor
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ #include <sys/types.h>
+ #include <fcntl.h>
+ #include <unistd.h>
+ int fcntl(
+ int fildes,
+ int cmd
+ );
+
+**STATUS CODES:**
+
+*EACCESS*
+ Search permission is denied for a direcotry in a file’s path
+ prefix.
+
+*EAGAIN*
+ The O_NONBLOCK flag is set for a file descriptor and the process
+ would be delayed in the I/O operation.
+
+*EBADF*
+ Invalid file descriptor
+
+*EDEADLK*
+ An ``fcntl`` with function F_SETLKW would cause a deadlock.
+
+*EINTR*
+ The functioin was interrupted by a signal.
+
+*EINVAL*
+ Invalid argument
+
+*EMFILE*
+ Too many file descriptor or in use by the process.
+
+*ENOLCK*
+ No locks available
+
+**DESCRIPTION:**
+
+``fcntl()`` performs one of various miscellaneous operations on``fd``. The operation in question is determined by ``cmd``:
+
+*F_DUPFD*
+ Makes ``arg`` be a copy of ``fd``, closing ``fd`` first if necessary.
+ The same functionality can be more easily achieved by using ``dup2()``.
+ The old and new descriptors may be used interchangeably. They share locks,
+ file position pointers and flags; for example, if the file position is
+ modified by using ``lseek()`` on one of the descriptors, the position is
+ also changed for the other.
+ The two descriptors do not share the close-on-exec flag, however. The
+ close-on-exec flag of the copy is off, meaning that it will be closed on
+ exec.
+ On success, the new descriptor is returned.
+
+*F_GETFD*
+ Read the close-on-exec flag. If the low-order bit is 0, the file will
+ remain open across exec, otherwise it will be closed.
+
+*F_SETFD*
+ Set the close-on-exec flag to the value specified by ``arg`` (only the least
+ significant bit is used).
+
+*F_GETFL*
+ Read the descriptor’s flags (all flags (as set by open()) are returned).
+
+*F_SETFL*
+ Set the descriptor’s flags to the value specified by ``arg``. Only``O_APPEND`` and ``O_NONBLOCK`` may be set.
+ The flags are shared between copies (made with ``dup()`` etc.) of the same
+ file descriptor.
+ The flags and their semantics are described in ``open()``.
+
+*F_GETLK, F_SETLK and F_SETLKW*
+ Manage discretionary file locks. The third argument ``arg`` is a pointer to a
+ struct flock (that may be overwritten by this call).
+
+*F_GETLK*
+ Return the flock structure that prevents us from obtaining the lock, or set the``l_type`` field of the lock to ``F_UNLCK`` if there is no obstruction.
+
+*F_SETLK*
+ The lock is set (when ``l_type`` is ``F_RDLCK`` or ``F_WRLCK``) or
+ cleared (when it is ``F_UNLCK``. If lock is held by someone else, this
+ call returns -1 and sets ``errno`` to EACCES or EAGAIN.
+
+*F_SETLKW*
+ Like ``F_SETLK``, but instead of returning an error we wait for the lock to
+ be released.
+
+*F_GETOWN*
+ Get the process ID (or process group) of the owner of a socket.
+ Process groups are returned as negative values.
+
+*F_SETOWN*
+ Set the process or process group that owns a socket.
+ For these commands, ownership means receiving ``SIGIO`` or ``SIGURG``
+ signals.
+ Process groups are specified using negative values.
+
+**NOTES:**
+
+The errors returned by ``dup2`` are different from those returned by``F_DUPFD``.
+
+lseek - Reposition read/write file offset
+-----------------------------------------
+.. index:: lseek
+.. index:: reposition read/write file offset
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ #include <sys/types.h>
+ #include <unistd.h>
+ int lseek(
+ int fildes,
+ off_t offset,
+ int whence
+ );
+
+**STATUS CODES:**
+
+*EBADF*
+ ``fildes`` is not an open file descriptor.
+
+*ESPIPE*
+ ``fildes`` is associated with a pipe, socket or FIFO.
+
+*EINVAL*
+ ``whence`` is not a proper value.
+
+**DESCRIPTION:**
+
+The ``lseek`` function repositions the offset of the file descriptor``fildes`` to the argument offset according to the directive whence.
+The argument ``fildes`` must be an open file descriptor. ``Lseek``
+repositions the file pointer fildes as follows:
+
+- If ``whence`` is SEEK_SET, the offset is set to ``offset`` bytes.
+
+- If ``whence`` is SEEK_CUR, the offset is set to its current location
+ plus offset bytes.
+
+- If ``whence`` is SEEK_END, the offset is set to the size of the
+ file plus ``offset`` bytes.
+
+The ``lseek`` function allows the file offset to be set beyond the end
+of the existing end-of-file of the file. If data is later written at this
+point, subsequent reads of the data in the gap return bytes of zeros
+(until data is actually written into the gap).
+
+Some devices are incapable of seeking. The value of the pointer associated
+with such a device is undefined.
+
+**NOTES:**
+
+NONE
+
+fsync - Synchronize file complete in-core state with that on disk
+-----------------------------------------------------------------
+.. index:: fsync
+.. index:: synchronize file complete in
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ int fsync(
+ int fd
+ );
+
+**STATUS CODES:**
+
+On success, zero is returned. On error, -1 is returned, and ``errno``
+is set appropriately.
+
+*EBADF*
+ ``fd`` is not a valid descriptor open for writing
+
+*EINVAL*
+ ``fd`` is bound to a special file which does not support support synchronization
+
+*EROFS*
+ ``fd`` is bound to a special file which does not support support synchronization
+
+*EIO*
+ An error occurred during synchronization
+
+**DESCRIPTION:**
+
+``fsync`` copies all in-core parts of a file to disk.
+
+**NOTES:**
+
+NONE
+
+fdatasync - Synchronize file in-core data with that on disk
+-----------------------------------------------------------
+.. index:: fdatasync
+.. index:: synchronize file in
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ int fdatasync(
+ int fd
+ );
+
+**STATUS CODES:**
+
+On success, zero is returned. On error, -1 is returned, and ``errno`` is
+set appropriately.
+
+*EBADF*
+ ``fd`` is not a valid file descriptor open for writing.
+
+*EINVAL*
+ ``fd`` is bound to a special file which does not support synchronization.
+
+*EIO*
+ An error occurred during synchronization.
+
+*EROFS*
+ ``fd`` is bound to a special file which dows not support synchronization.
+
+**DESCRIPTION:**
+
+``fdatasync`` flushes all data buffers of a file to disk (before the system call
+returns). It resembles ``fsync`` but is not required to update the metadata such
+as access time.
+
+Applications that access databases or log files often write a tiny data fragment
+(e.g., one line in a log file) and then call ``fsync`` immediately in order to
+ensure that the written data is physically stored on the harddisk. Unfortunately,
+fsync will always initiate two write operations: one for the newly written data and
+another one in order to update the modification time stored in the inode. If the
+modification time is not a part of the transaction concept ``fdatasync`` can be
+used to avoid unnecessary inode disk write operations.
+
+**NOTES:**
+
+NONE
+
+sync - Schedule file system updates
+-----------------------------------
+.. index:: sync
+.. index:: synchronize file systems
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ void sync(void);
+
+**STATUS CODES:**
+
+NONE
+
+**DESCRIPTION:**
+
+The ``sync`` service causes all information in memory that updates
+file systems to be scheduled for writing out to all file systems.
+
+**NOTES:**
+
+The writing of data to the file systems is only guaranteed to be
+scheduled upon return. It is not necessarily complete upon return
+from ``sync``.
+
+mount - Mount a file system
+---------------------------
+.. index:: mount
+.. index:: mount a file system
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ #include <libio.h>
+ int mount(
+ rtems_filesystem_mount_table_entry_t \**mt_entry,
+ rtems_filesystem_operations_table \*fs_ops,
+ rtems_filesystem_options_t fsoptions,
+ char \*device,
+ char \*mount_point
+ );
+
+**STATUS CODES:**
+
+*EXXX*
+
+**DESCRIPTION:**
+
+The ``mount`` routines mounts the filesystem class
+which uses the filesystem operations specified by ``fs_ops``
+and ``fsoptions``. The filesystem is mounted at the directory``mount_point`` and the mode of the mounted filesystem is
+specified by ``fsoptions``. If this filesystem class requires
+a device, then the name of the device must be specified by ``device``.
+
+If this operation succeeds, the mount table entry for the mounted
+filesystem is returned in ``mt_entry``.
+
+**NOTES:**
+
+NONE
+
+unmount - Unmount file systems
+------------------------------
+.. index:: unmount
+.. index:: unmount file systems
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ #include <libio.h>
+ int unmount(
+ const char \*mount_path
+ );
+
+**STATUS CODES:**
+
+*EXXX*
+
+**DESCRIPTION:**
+
+The ``unmount`` routine removes the attachment of the filesystem specified
+by ``mount_path``.
+
+**NOTES:**
+
+NONE
+
+readv - Vectored read from a file
+---------------------------------
+.. index:: readv
+.. index:: vectored read from a file
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ #include <sys/uio.h>
+ ssize_t readv(
+ int fd,
+ const struct iovec \*iov,
+ int iovcnt
+ );
+
+**STATUS CODES:**
+
+In addition to the errors detected by``Input and Output Primitives Manager read - Reads from a file, read()``,
+this routine may return -1 and sets ``errno`` based upon the following
+errors:
+
+*EINVAL*
+ The sum of the ``iov_len`` values in the iov array overflowed an``ssize_t``.
+
+*EINVAL*
+ The ``iovcnt`` argument was less than or equal to 0, or greater
+ than ``IOV_MAX``.
+
+**DESCRIPTION:**
+
+The ``readv()`` function is equivalent to ``read()``
+except as described here. The ``readv()`` function shall place
+the input data into the ``iovcnt`` buffers specified by the
+members of the ``iov`` array: ``iov[0], iov[1], ..., iov[iovcnt-1]``.
+
+Each ``iovec`` entry specifies the base address and length of an area
+in memory where data should be placed. The ``readv()`` function
+always fills an area completely before proceeding to the next.
+
+**NOTES:**
+
+NONE
+
+writev - Vectored write to a file
+---------------------------------
+.. index:: writev
+.. index:: vectored write to a file
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ #include <sys/uio.h>
+ ssize_t writev(
+ int fd,
+ const struct iovec \*iov,
+ int iovcnt
+ );
+
+**STATUS CODES:**
+
+In addition to the errors detected by``Input and Output Primitives Manager write - Write to a file, write()``,
+this routine may return -1 and sets ``errno`` based upon the following
+errors:
+
+*EINVAL*
+ The sum of the ``iov_len`` values in the iov array overflowed an``ssize_t``.
+
+*EINVAL*
+ The ``iovcnt`` argument was less than or equal to 0, or greater
+ than ``IOV_MAX``.
+
+**DESCRIPTION:**
+
+The ``writev()`` function is equivalent to ``write()``,
+except as noted here. The ``writev()`` function gathers output
+data from the ``iovcnt`` buffers specified by the members of
+the ``iov array``: ``iov[0], iov[1], ..., iov[iovcnt-1]``.
+The ``iovcnt`` argument is valid if greater than 0 and less
+than or equal to ``IOV_MAX``.
+
+Each ``iovec`` entry specifies the base address and length of
+an area in memory from which data should be written. The ``writev()``
+function always writes a complete area before proceeding to the next.
+
+If ``fd`` refers to a regular file and all of the ``iov_len``
+members in the array pointed to by ``iov`` are 0, ``writev()``
+returns 0 and has no other effect. For other file types, the behavior
+is unspecified by POSIX.
+
+**NOTES:**
+
+NONE
+
+aio_read - Asynchronous Read
+----------------------------
+.. index:: aio_read
+.. index:: asynchronous read
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ int aio_read(
+ );
+
+**STATUS CODES:**
+
+*E*
+ The
+
+**DESCRIPTION:**
+
+**NOTES:**
+
+This routine is not currently supported by RTEMS but could be
+in a future version.
+
+aio_write - Asynchronous Write
+------------------------------
+.. index:: aio_write
+.. index:: asynchronous write
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ int aio_write(
+ );
+
+**STATUS CODES:**
+
+*E*
+ The
+
+**DESCRIPTION:**
+
+**NOTES:**
+
+This routine is not currently supported by RTEMS but could be
+in a future version.
+
+lio_listio - List Directed I/O
+------------------------------
+.. index:: lio_listio
+.. index:: list directed i/o
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ int lio_listio(
+ );
+
+**STATUS CODES:**
+
+*E*
+ The
+
+**DESCRIPTION:**
+
+**NOTES:**
+
+This routine is not currently supported by RTEMS but could be
+in a future version.
+
+aio_error - Retrieve Error Status of Asynchronous I/O Operation
+---------------------------------------------------------------
+.. index:: aio_error
+.. index:: retrieve error status of asynchronous i/o operation
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ int aio_error(
+ );
+
+**STATUS CODES:**
+
+*E*
+ The
+
+**DESCRIPTION:**
+
+**NOTES:**
+
+This routine is not currently supported by RTEMS but could be
+in a future version.
+
+aio_return - Retrieve Return Status Asynchronous I/O Operation
+--------------------------------------------------------------
+.. index:: aio_return
+.. index:: retrieve return status asynchronous i/o operation
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ int aio_return(
+ );
+
+**STATUS CODES:**
+
+*E*
+ The
+
+**DESCRIPTION:**
+
+**NOTES:**
+
+This routine is not currently supported by RTEMS but could be
+in a future version.
+
+aio_cancel - Cancel Asynchronous I/O Request
+--------------------------------------------
+.. index:: aio_cancel
+.. index:: cancel asynchronous i/o request
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ int aio_cancel(
+ );
+
+**STATUS CODES:**
+
+*E*
+ The
+
+**DESCRIPTION:**
+
+**NOTES:**
+
+This routine is not currently supported by RTEMS but could be
+in a future version.
+
+aio_suspend - Wait for Asynchronous I/O Request
+-----------------------------------------------
+.. index:: aio_suspend
+.. index:: wait for asynchronous i/o request
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ int aio_suspend(
+ );
+
+**STATUS CODES:**
+
+*E*
+ The
+
+**DESCRIPTION:**
+
+**NOTES:**
+
+This routine is not currently supported by RTEMS but could be
+in a future version.
+
+aio_fsync - Asynchronous File Synchronization
+---------------------------------------------
+.. index:: aio_fsync
+.. index:: asynchronous file synchronization
+
+**CALLING SEQUENCE:**
+
+.. code:: c
+
+ int aio_fsync(
+ );
+
+**STATUS CODES:**
+
+*E*
+ The
+
+**DESCRIPTION:**
+
+**NOTES:**
+
+This routine is not currently supported by RTEMS but could be
+in a future version.
+
+.. COMMENT: COPYRIGHT (c) 1988-2002.
+
+.. COMMENT: On-Line Applications Research Corporation (OAR).
+
+.. COMMENT: All rights reserved.
+
generated by cgit v1.2.3 (git 2.25.1) at 2024-04-18 23:38:50 +0000