writev - phpMan

READV(2)                   Linux Programmer’s Manual                  READV(2)



NAME
       readv, writev - read or write data into multiple buffers

SYNOPSIS
       #include <sys/uio.h>

       ssize_t readv(int fd, const struct iovec *vector, int count);

       ssize_t writev(int fd, const struct iovec *vector, int count);

DESCRIPTION
       The  readv()  function  reads  count  blocks from the file associated with the file
       descriptor fd into the multiple buffers described by vector.

       The writev() function writes at most count blocks described by vector to  the  file
       associated with the file descriptor fd.

       The pointer vector points to a struct iovec defined in <sys/uio.h> as

          struct iovec {
              void *iov_base;   /* Starting address */
              size_t iov_len;   /* Number of bytes */
          };

       Buffers are processed in the order specified.

       The  readv()  function  works  just  like  read(2) except that multiple buffers are
       filled.

       The writev() function works just like write(2) except  that  multiple  buffers  are
       written out.


RETURN VALUE
       On  success,  the  readv()  function returns the number of bytes read; the writev()
       function returns the number of bytes written.  On error, -1 is returned, and  errno
       is set appropriately.

ERRORS
       The errors are as given for read(2) and write(2).  Additionally the following error
       is defined.

       EINVAL The sum of the iov_len values overflows an ssize_t  value.  Or,  the  vector
              count count is zero or greater than IOV_MAX.

CONFORMING TO
       4.4BSD  (the  readv  and writev functions first appeared in BSD 4.2), Unix98, POSIX
       1003.1-2001.  Linux libc5 used size_t as the type of the count parameter,  and  int
       as return type for these functions.

BUGS
       It is not advisable to mix calls to functions like readv() or writev(), which oper-
       ate on file descriptors, with the functions from the  stdio  library;  the  results
       will be undefined and probably not what you want.

SEE ALSO
       read(2), write(2)



                                  2002-10-17                          READV(2)

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