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 1.4
       Copyright (C) 2009 Peter Miller

                                                                                                explain_readv(3)