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NAME

       explain_fileno - explain fileno(3) errors

SYNOPSIS

       #include <libexplain/fileno.h>
       const char *explain_fileno(FILE *fp);
       const char *explain_errno_fileno(int errnum, FILE *fp);
       void explain_message_fileno(char *message, int message_size, FILE *fp);
       void explain_message_errno_fileno(char *message, int message_size, int
       errnum, FILE *fp);

DESCRIPTION

       These  functions may be used to obtain explanations for errors returned
       by the fileno(3) system call.

   explain_fileno
       const char *explain_fileno(FILE *fp);

       The explain_fileno function is used to  obtain  an  explanation  of  an
       error returned by the fileno(3) 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.

       fp      The original fp, exactly as  passed  to  the  fileno(3)  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:
              if (fileno(fp) < 0)
              {
                  fprintf(stderr, "%s\n", explain_fileno(fp));
                  exit(EXIT_FAILURE);
              }

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

   explain_errno_fileno
       const char *explain_errno_fileno(int errnum, FILE *fp);

       The explain_errno_fileno function is used to obtain an  explanation  of
       an  error  returned by the fileno(3) 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.

       fp      The  original  fp,  exactly  as  passed to the fileno(3) 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:
              if (fileno(fp) < 0)
              {
                  int err = errno;
                  fprintf(stderr, "%s\n", explain_errno_fileno(err, fp));
                  exit(EXIT_FAILURE);
              }

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

   explain_message_fileno
       void explain_message_fileno(char *message, int message_size, FILE *fp);

       The explain_message_fileno function is used to obtain an explanation of
       an  error  returned by the fileno(3) 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.

       fp      The  original  fp,  exactly  as  passed to the fileno(3) system
               call.

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

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

   explain_message_errno_fileno
       void explain_message_errno_fileno(char *message, int message_size, int
       errnum, FILE *fp);

       The   explain_message_errno_fileno   function  is  used  to  obtain  an
       explanation of an error returned by  the  fileno(3)  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.

       fp      The original fp, exactly as  passed  to  the  fileno(3)  system
               call.

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

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

SEE ALSO

       fileno(3)
               check and reset stream status

       explain_fileno_or_die(3)
               check and reset stream status and report errors

COPYRIGHT

       libexplain version 0.19
       Copyright (C) 2009 Peter Miller

                                                             explain_fileno(3)