explain_ferror(3)					     Library Functions Manual						 explain_ferror(3)

NAME

       explain_ferror - explain ferror(3) errors

SYNOPSIS

       #include <libexplain/ferror.h>
       const char *explain_ferror(FILE *fp);
       const char *explain_errno_ferror(int errnum, FILE *fp);
       void explain_message_ferror(char *message, int message_size, FILE *fp);
       void explain_message_errno_ferror(char *message, int message_size, int errnum, FILE *fp);

DESCRIPTION

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

   explain_ferror
       const char *explain_ferror(FILE *fp);

       The explain_ferror function is used to obtain an explanation of an error returned by the ferror(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.

       This function is intended to be used in a fashion similar to the following example:
	      if (ferror(fp) < 0)
	      {
		  fprintf(stderr, "%s
", explain_ferror(fp));
		  exit(EXIT_FAILURE);
	      }

       It is essential that this function cal be placed as close as possible to the I/O code that has caused the  problem,  otherwise  intervening
       code could have altered the errno global variable.

       fp      The original fp, exactly as passed to the ferror(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.

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

       The  explain_errno_ferror  function is used to obtain an explanation of an error returned by the ferror(3) system call.	The least the mes-
       sage will contain is the value of strerror(errnum), but usually it will do much better, and indicate the underlying cause in more detail.

       This function is intended to be used in a fashion similar to the following example:
	      if (ferror(fp) < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s
", explain_errno_ferror(err, fp));
		  exit(EXIT_FAILURE);
	      }

       It is essential that this function cal be placed as close as possible to the I/O code that has caused the  problem,  otherwise  intervening
       code could have altered the errno global variable.

       errnum  The error value to be decoded, usually obtained from the errno global variable just before this function is called.  This is neces-
	       sary 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 ferror(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.

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

       The explain_message_ferror function may be used to  obtain an explanation of an error returned by the ferror(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.

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

       It is essential that this function cal be placed as close as possible to the I/O code that has caused the  problem,  otherwise  intervening
       code could have altered the errno global variable.

       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 ferror(3) system call.

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

       The explain_message_errno_ferror function may be used to obtain an explanation of an error returned by  the  ferror(3)  system  call.   The
       least  the  message will contain is the value of strerror(errnum), but usually it will do much better, and indicate the underlying cause in
       more detail.

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

       It is essential that this function cal be placed as close as possible to the I/O code that has caused the  problem,  otherwise  intervening
       code could have altered the errno global variable.

       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 neces-
	       sary 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 ferror(3) system call.

SEE ALSO

       ferror(3)
	       check stream status

       explain_ferror_or_die(3)
	       check stream status and report errors

COPYRIGHT

       libexplain version 0.52
       Copyright (C) 2008 Peter Miller

																 explain_ferror(3)