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NAME

       explain_writev - explain writev(2) errors

SYNOPSIS

       #include <libexplain/writev.h>
       const char *explain_writev(int fildes, const struct iovec *data, int
       data_size);
       const char *explain_errno_writev(int errnum, int fildes, const struct
       iovec *data, int data_size);
       void explain_message_writev(char *message, int message_size, int
       fildes, const struct iovec *data, int data_size);
       void explain_message_errno_writev(char *message, int message_size, int
       errnum, int fildes, const struct iovec *data, int data_size);

DESCRIPTION

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

   explain_writev
       const char *explain_writev(int fildes, const struct iovec *data, int
       data_size);

       The  explain_writev  function  is  used  to obtain an explanation of an
       error returned by the writev(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 writev(2) system
               call.

       data    The original data, exactly as passed to  the  writev(2)  system
               call.

       data_size
               The  original  data_size,  exactly  as  passed to the writev(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 = writev(fildes, data, data_size);
              if (result < 0)
              {
                  fprintf(stderr, "%s\n", explain_writev(fildes, data,
                  data_size));
                  exit(EXIT_FAILURE);
              }

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

   explain_errno_writev
       const char *explain_errno_writev(int errnum, int fildes, const struct
       iovec *data, int data_size);

       The  explain_errno_writev  function is used to obtain an explanation of
       an error returned by the writev(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 writev(2)  system
               call.

       data    The  original  data,  exactly as passed to the writev(2) system
               call.

       data_size
               The original data_size, exactly  as  passed  to  the  writev(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 = writev(fildes, data, data_size);
              if (result < 0)
              {
                  int err = errno;
                  fprintf(stderr, "%s\n", explain_errno_writev(err, fildes,
                  data, data_size));
                  exit(EXIT_FAILURE);
              }

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

   explain_message_writev
       void explain_message_writev(char *message, int message_size, int
       fildes, const struct iovec *data, int data_size);

       The explain_message_writev function is used to obtain an explanation of
       an  error  returned by the writev(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 writev(2) system
               call.

       data    The original data, exactly as passed to  the  writev(2)  system
               call.

       data_size
               The  original  data_size,  exactly  as  passed to the writev(2)
               system call.

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

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

   explain_message_errno_writev
       void explain_message_errno_writev(char *message, int message_size, int
       errnum, int fildes, const struct iovec *data, int data_size);

       The  explain_message_errno_writev  function  is  used  to   obtain   an
       explanation  of  an  error  returned  by the writev(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 writev(2) system
               call.

       data    The original data, exactly as passed to  the  writev(2)  system
               call.

       data_size
               The  original  data_size,  exactly  as  passed to the writev(2)
               system call.

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

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

SEE ALSO

       writev(2)
               write data from multiple buffers

       explain_writev_or_die(3)
               write data from multiple buffers and report errors

COPYRIGHT

       libexplain version 0.19
       Copyright (C) 2009 Peter Miller

                                                             explain_writev(3)