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NAME

       explain_eventfd - explain eventfd(2) errors

SYNOPSIS

       #include <libexplain/eventfd.h>
       const char *explain_eventfd(unsigned int initval, int flags);
       const char *explain_errno_eventfd(int errnum, unsigned int initval, int
       flags);
       void explain_message_eventfd(char *message, int message_size, unsigned
       int initval, int flags);
       void explain_message_errno_eventfd(char *message, int message_size, int
       errnum, unsigned int initval, int flags);

DESCRIPTION

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

   explain_eventfd
       const char *explain_eventfd(unsigned int initval, int flags);

       The  explain_eventfd  function  is  used to obtain an explanation of an
       error returned by the eventfd(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.

       initval The  original  initval,  exactly  as  passed  to the eventfd(2)
               system call.

       flags   The original flags, exactly as passed to the eventfd(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:
              int result = eventfd(initval, flags);
              if (result < 0)
              {
                  fprintf(stderr, "%s\n", explain_eventfd(initval, flags));
                  exit(EXIT_FAILURE);
              }

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

   explain_errno_eventfd
       const char *explain_errno_eventfd(int errnum, unsigned int initval, int
       flags);

       The  explain_errno_eventfd function is used to obtain an explanation of
       an error returned by the eventfd(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.

       initval The original initval,  exactly  as  passed  to  the  eventfd(2)
               system call.

       flags   The  original flags, exactly as passed to the eventfd(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:
              int result = eventfd(initval, flags);
              if (result < 0)
              {
                  int err = errno;
                  fprintf(stderr, "%s\n", explain_errno_eventfd(err, initval,
                  flags));
                  exit(EXIT_FAILURE);
              }

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

   explain_message_eventfd
       void explain_message_eventfd(char *message, int message_size, unsigned
       int initval, int flags);

       The  explain_message_eventfd  function is used to obtain an explanation
       of an error returned by the  eventfd(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.

       initval The  original  initval,  exactly  as  passed  to the eventfd(2)
               system call.

       flags   The original flags, exactly as passed to the eventfd(2)  system
               call.

       Example:  This  function is intended to be used in a fashion similar to
       the following example:
              int result = eventfd(initval, flags);
              if (result < 0)
              {
                  char message[3000];
                  explain_message_eventfd(message, sizeof(message), initval,
                  flags);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

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

   explain_message_errno_eventfd
       void explain_message_errno_eventfd(char *message, int message_size, int
       errnum, unsigned int initval, int flags);

       The   explain_message_errno_eventfd  function  is  used  to  obtain  an
       explanation of an error returned by the  eventfd(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.

       initval The original initval,  exactly  as  passed  to  the  eventfd(2)
               system call.

       flags   The  original flags, exactly as passed to the eventfd(2) system
               call.

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

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

SEE ALSO

       eventfd(2)
               create a file descriptor for event notification

       explain_eventfd_or_die(3)
               create  a  file  descriptor  for  event notification and report
               errors

COPYRIGHT

       libexplain version 0.19
       Copyright (C) 2009 Peter Miller

                                                            explain_eventfd(3)