READ(2) BSD System Calls Manual READ(2)

NAME
     pprreeaadd, rreeaadd, rreeaaddvv - read input

LLIIBBRRAARRYY
     Standard C Library (libc, -lc)

SYNOPSIS
     ##iinncclluuddee <>
     ##iinncclluuddee <>
     ##iinncclluuddee <>

     ssizet
     pprreeaadd(int d, void *buf, sizet nbyte, offt offset);

     ssizet
     rreeaadd(int fildes, void *buf, sizet nbyte);

     ssizet
     rreeaaddvv(int d, const struct iovec *iov, int iovcnt);

DESCRIPTION
     RReeaadd() attempts to read nbyte bytes of data from the object referenced by
     the descriptor fildes into the buffer pointed to by buf.  RReeaaddvv() per-
     forms the same action, but scatters the input data into the iovcnt
     buffers specified by the members of the iov array: iov[0], iov[1], ...,
     iov[iovcnt-1].  PPrreeaadd() performs the same function, but reads from the
     specified position in the file without modifying the file pointer.

     For rreeaaddvv(), the iovec structure is defined as:

           struct iovec {
                   char   *iovbase;  /* Base address. */
                   sizet iovlen;    /* Length. */
           };

     Each iovec entry specifies the base address and length of an area in mem-
     ory where data should be placed.  RReeaaddvv() will always fill an area com-
     pletely before proceeding to the next.

     On objects capable of seeking, the rreeaadd() starts at a position given by
     the pointer associated with fildes (see lseek(2)).  Upon return from
     rreeaadd(), the pointer is incremented by the number of bytes actually read.

     Objects that are not capable of seeking always read from the current
     position.  The value of the pointer associated with such an object is
     undefined.

     Upon successful completion, rreeaadd(), rreeaaddvv(), and pprreeaadd() return the num-
     ber of bytes actually read and placed in the buffer.  The system guaran-
     tees to read the number of bytes requested if the descriptor references a
     normal file that has that many bytes left before the end-of-file, but in
     no other case.

RETURN VALUES
     If successful, the number of bytes actually read is returned.  Upon read-
     ing end-of-file, zero is returned.  Otherwise, a -1 is returned and the
     global variable errno is set to indicate the error.

EERRRROORRSS
     The pprreeaadd(), rreeaadd(), and rreeaaddvv() calls will succeed unless:

     [EAGAIN]           The file was marked for non-blocking I/O, and no data
                        were ready to be read.

     [EBADF]            fildes is not a valid file or socket descriptor open
                        for reading.

     [EFAULT]           Buf points outside the allocated address space.

     [EINTR]            A read from a slow device was interrupted before any
                        data arrived by the delivery of a signal.

     [EINVAL]           The pointer associated with fildes was negative.

     [EIO]              An I/O error occurred while reading from the file sys-
                        tem.

     [EIO]              The process group is orphaned.

     [EIO]              The file is a regular file, nbyte is greater than 0,
                        the starting position is before the end-of-file, and
                        the starting position is greater than or equal to the
                        offset maximum established for the open file descrip-
                        tor associated with fildes.

     [EISDIR]           An attempt is made to read a directory.

     [ENOBUFS]          An attempt to allocate a memory buffer fails.

     [ENOMEM]           Insufficient memory is available.

     [ENXIO]            An action is requested of a device that does not
                        exist..

     [ENXIO]            A requested action cannot be performed by the device.

     The pprreeaadd() call may also return the following errors:

     [EINVAL]           The specified file offset is invalid.

     [ESPIPE]           The file descriptor is associated with a pipe, socket,
                        or FIFO.

     The rreeaadd() call may also return the following errors:

     [ECONNRESET]       The connection is closed by the peer during a read
                        attempt on a socket.

     [ENOTCONN]         A read is attempted on an unconnected socket.

     [ETIMEDOUT]        A transmission timeout occurs during a read attempt on
                        a socket.

     The rreeaaddvv() call may also return one of the following errors:

     [EFAULT]           Part of the iov points outside the process's allocated
                        address space.

     [EINVAL]           Iovcnt was less than or equal to 0, or greater than
                        16.

     [EINVAL]           One of the iovlen values in the iov array was nega-
                        tive.

     [EINVAL]           The sum of the iovlen values in the iov array over-
                        flowed a 32-bit integer.

LEGACY SYNOPSIS
     ##iinncclluuddee <>
     ##iinncclluuddee <>
     ##iinncclluuddee <>

     The include files  and  are necessary for all
     functions.

SEE ALSO
     dup(2), fcntl(2), open(2), pipe(2), select(2), socket(2), socketpair(2),
     compat(5)

STANDARDS
     The rreeaadd() function call is expected to conform to ISO/IEC 9945-1:1990
     (``POSIX.1'').  The rreeaaddvv() and pprreeaadd() functions are expected to conform
     to X/Open Portability Guide Issue 4, Version 2 (``XPG4.2'').

HISTORY     The pprreeaadd() function call appeared in AT&T System V.4 UNIX.  The rreeaaddvv()
     function call appeared in 4.2BSD.  A rreeaadd() function call appeared in
     Version 6 AT&T UNIX.

BSD                            February 26, 1994                           BSD