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RedHat 9 (Linux i386) - man page for writev (redhat section 3)

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READV(3)			    Linux Programmer's Manual				 READV(3)

       readv, writev - read or write data into multiple buffers

       #include <sys/uio.h>

       int readv(int filedes, const struct iovec *vector,
		 size_t count);

       int writev(int filedes, const struct iovec *vector,
		 size_t count);

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

       The writev() function writes at most count blocks described by vector to the file  associ-
       ated with the file descriptor filedes.

       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 vector[0], vector[1], ... vector[count].

       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

       The readv() function returns the number of bytes or -1 on  error;  the  writev()  function
       returns the number of bytes written.

       The readv() and writev() functions can fail and set errno to the following values:

       EBADF  fd is not a valid file descriptor.

       EINVAL fd is unsuitable for reading (for readv()) or writing (for writev()).

       EFAULT buf is outside the processes' address space.

       EAGAIN Non-blocking I/O had been selected in the open() call, and reading or writing could
	      not be done immediately.

       EINTR  Reading or writing was interrupted before any data was transferred.


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

       read(2), write(2)

GNU					    1993-04-25					 READV(3)
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