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NAME

       explain_readv - explain readv(2) errors

SYNOPSIS

       #include <libexplain/readv.h>
       const char *explain_readv(int fildes, const struct iovec *iov, int
       iovcnt);
       const char *explain_errno_readv(int errnum, int fildes, const struct
       iovec *iov, int iovcnt);
       void explain_message_readv(char *message, int message_size, int fildes,
       const struct iovec *iov, int iovcnt);
       void explain_message_errno_readv(char *message, int message_size, int
       errnum, int fildes, const struct iovec *iov, int iovcnt);

DESCRIPTION

       These  functions may be used to obtain explanations for errors returned
       by the readv(2) system call.

   explain_readv
       const char *explain_readv(int fildes, const struct iovec *iov, int
       iovcnt);

       The explain_readv function is used to obtain an explanation of an error
       returned by the readv(2)  system  call.  The  least  the  message  will
       contain  is  the  value of strerror(errno), but usually it will do much
       better, and indicate the underlying cause in more detail.

       The errno global variable will be used to obtain the error value to  be
       decoded.

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

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

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

       Returns:
               The message explaining the error. This message buffer is shared
               by  all  libexplain  functions  which do not supply a buffer in
               their argument list.  This will be overwritten by the next call
               to  any libexplain function which shares this buffer, including
               other threads.

       Note: This function is not thread safe,  because  it  shares  a  return
       buffer across all threads, and many other functions in this library.

       Example:  This  function is intended to be used in a fashion similar to
       the following example:
              ssize_t result = readv(fildes, iov, iovcnt);
              if (result < 0)
              {
                  fprintf(stderr, "%s\n", explain_readv(fildes, iov, iovcnt));
                  exit(EXIT_FAILURE);
              }

       The   above   code   example   is   available   pre-packaged   as   the
       explain_readv_or_die(3) function.

   explain_errno_readv
       const char *explain_errno_readv(int errnum, int fildes, const struct
       iovec *iov, int iovcnt);

       The explain_errno_readv function is used to obtain an explanation of an
       error returned by the readv(2) system call. The least the message  will
       contain  is  the  value of strerror(errno), but usually it will do much
       better, and indicate the underlying cause in more detail.

       errnum  The error value to be decoded, usually obtained from the  errno
               global  variable  just  before this function is called. This is
               necessary if you need to call any code between the system  call
               to  be explained and this function, because many libc functions
               will alter the value of errno.

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

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

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

       Returns:
               The message explaining the error. This message buffer is shared
               by all libexplain functions which do not  supply  a  buffer  in
               their argument list.  This will be overwritten by the next call
               to any libexplain function which shares this buffer,  including
               other threads.

       Note:  This  function  is  not  thread safe, because it shares a return
       buffer across all threads, and many other functions in this library.

       Example: This function is intended to be used in a fashion  similar  to
       the following example:
              ssize_t result = readv(fildes, iov, iovcnt);
              if (result < 0)
              {
                  int err = errno;
                  fprintf(stderr, "%s\n", explain_errno_readv(err, fildes,
                  iov, iovcnt));
                  exit(EXIT_FAILURE);
              }

       The   above   code   example   is   available   pre-packaged   as   the
       explain_readv_or_die(3) function.

   explain_message_readv
       void explain_message_readv(char *message, int message_size, int fildes,
       const struct iovec *iov, int iovcnt);

       The explain_message_readv function is used to obtain an explanation  of
       an  error  returned  by the readv(2) system call. The least the message
       will contain is the value of strerror(errno), but usually  it  will  do
       much better, and indicate the underlying cause in more detail.

       The  errno global variable will be used to obtain the error value to be
       decoded.

       message The location in which to  store  the  returned  message.  If  a
               suitable  message  return  buffer is supplied, this function is
               thread safe.

       message_size
               The size in bytes  of  the  location  in  which  to  store  the
               returned message.

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

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

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

       Example: This function is intended to be used in a fashion  similar  to
       the following example:
              ssize_t result = readv(fildes, iov, iovcnt);
              if (result < 0)
              {
                  char message[3000];
                  explain_message_readv(message, sizeof(message), fildes, iov,
                  iovcnt);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

       The   above   code   example   is   available   pre-packaged   as   the
       explain_readv_or_die(3) function.

   explain_message_errno_readv
       void explain_message_errno_readv(char *message, int message_size, int
       errnum, int fildes, const struct iovec *iov, int iovcnt);

       The  explain_message_errno_readv  function  is  used   to   obtain   an
       explanation of an error returned by the readv(2) system call. The least
       the message will contain is the value of strerror(errno),  but  usually
       it  will  do  much  better,  and  indicate the underlying cause in more
       detail.

       message The location in which to  store  the  returned  message.  If  a
               suitable  message  return  buffer is supplied, this function is
               thread safe.

       message_size
               The size in bytes  of  the  location  in  which  to  store  the
               returned message.

       errnum  The  error value to be decoded, usually obtained from the errno
               global variable just before this function is  called.  This  is
               necessary  if you need to call any code between the system call
               to be explained and this function, because many libc  functions
               will alter the value of errno.

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

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

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

       Example: This function is intended to be used in a fashion  similar  to
       the following example:
              ssize_t result = readv(fildes, iov, iovcnt);
              if (result < 0)
              {
                  int err = errno;
                  char message[3000];
                  explain_message_errno_readv(message, sizeof(message), err,
                  fildes, iov, iovcnt);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

       The   above   code   example   is   available   pre-packaged   as   the
       explain_readv_or_die(3) function.

SEE ALSO

       readv(2)
               read data into multiple buffers

       explain_readv_or_die(3)
               read data into multiple buffers and report errors

COPYRIGHT

       libexplain version 0.19
       Copyright (C) 2009 Peter Miller

                                                              explain_readv(3)