explain_readv_or_die(3) [debian man page]

explain_readv_or_die(3) 				     Library Functions Manual					   explain_readv_or_die(3)

NAME

       explain_readv_or_die - read data into multiple buffers and report errors

SYNOPSIS

       #include <libexplain/readv.h>
       ssize_t explain_readv_or_die(int fildes, const struct iovec *iov, int iovcnt);
       ssize_t explain_readv_on_error(int fildes, const struct iovec *iov, int iovcnt);

DESCRIPTION

       The  explain_readv_or_die  function is used to call the readv(2) system call. On failure an explanation will be printed to stderr, obtained
       from the explain_readv(3) function, and then the process terminates by calling exit(EXIT_FAILURE).

       The explain_readv_on_error function is used to call the readv(2) system call. On failure an explanation will be printed to stderr, obtained
       from the explain_readv(3) function, but still returns to the caller.

       fildes  The fildes, exactly as to be passed to the readv(2) system call.

       iov     The iov, exactly as to be passed to the readv(2) system call.

       iovcnt  The iovcnt, exactly as to be passed to the readv(2) system call.

RETURN VALUE

       The  explain_readv_or_die function only returns on success, see readv(2) for more information. On failure, prints an explanation and exits,
       it does not return.

       The explain_readv_on_error function always returns the value return by the wrapped readv(2) system call.

EXAMPLE

       The explain_readv_or_die function is intended to be used in a fashion similar to the following example:
	      ssize_t result = explain_readv_or_die(fildes, iov, iovcnt);

SEE ALSO

       readv(2)
	       read data into multiple buffers

       explain_readv(3)
	       explain readv(2) errors

       exit(2) terminate the calling process

COPYRIGHT

       libexplain version 0.52
       Copyright (C) 2009 Peter Miller

															   explain_readv_or_die(3)

READV(3P)						     POSIX Programmer's Manual							 READV(3P)

PROLOG

       This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
       ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME

       readv - read a vector

SYNOPSIS

       #include <sys/uio.h>

       ssize_t readv(int fildes, const struct iovec *iov, int iovcnt);

DESCRIPTION

       The readv() function shall be equivalent to read(), except as described below. 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].  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 where data should be placed. The readv() function shall  always
       fill an area completely before proceeding to the next.

       Upon successful completion, readv() shall mark for update the st_atime field of the file.

RETURN VALUE

       Refer to read().

ERRORS

       Refer to read().

       In addition, the readv() function shall fail if:

       EINVAL The sum of the iov_len values in the iov array overflowed an ssize_t.

       The readv() function may fail if:

       EINVAL The iovcnt argument was less than or equal to 0, or greater than {IOV_MAX}.

       The following sections are informative.

EXAMPLES

   Reading Data into an Array
       The  following  example	reads  data  from the file associated with the file descriptor fd into the buffers specified by members of the iov
       array.

	      #include <sys/types.h>
	      #include <sys/uio.h>
	      #include <unistd.h>
	      ...
	      ssize_t bytes_read;
	      int fd;
	      char buf0[20];
	      char buf1[30];
	      char buf2[40];
	      int iovcnt;
	      struct iovec iov[3];

	      iov[0].iov_base = buf0;
	      iov[0].iov_len = sizeof(buf0);
	      iov[1].iov_base = buf1;
	      iov[1].iov_len = sizeof(buf1);
	      iov[2].iov_base = buf2;
	      iov[2].iov_len = sizeof(buf2);
	      ...
	      iovcnt = sizeof(iov) / sizeof(struct iovec);

	      bytes_read = readv(fd, iov, iovcnt);
	      ...

APPLICATION USAGE

       None.

RATIONALE

       Refer to read().

FUTURE DIRECTIONS

       None.

SEE ALSO

       read(), writev(), the Base Definitions volume of IEEE Std 1003.1-2001, <sys/uio.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and  the  original  IEEE
       and  The  Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003								 READV(3P)