explain_fprintf(3)					     Library Functions Manual						explain_fprintf(3)

NAME

       explain_fprintf - explain fprintf(3) errors

SYNOPSIS

       #include <libexplain/fprintf.h>
       const char *explain_fprintf(FILE *fp, const char *format, ...);
       const char *explain_errno_fprintf(int errnum, FILE *fp, const char *format, ...);
       void explain_message_fprintf(char *message, int message_size, FILE *fp, const char *format, ....);
       void explain_message_errno_fprintf(char *message, int message_size, int errnum, FILE *fp, const char *format, ...);

DESCRIPTION

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

   explain_fprintf
       const char *explain_fprintf(FILE *fp, const char *format, ...);

       The  explain_fprintf  function  is  used to obtain an explanation of an error returned by the fprintf(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 fprintf(3) system call.

       format  The original format, exactly as passed to the fprintf(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:
	      errno = EINVAL;
	      int result = fprintf(fp, format, ...);
	      if (result < 0)
	      {
		  fprintf(stderr, "%s
", explain_fprintf(fp, format, ...));
		  exit(EXIT_FAILURE);
	      }

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

   explain_errno_fprintf
       const char *explain_errno_fprintf(int errnum, FILE *fp, const char *format, ...);

       The explain_errno_fprintf function is used to obtain an explanation of an error returned by the fprintf(3) system call. The least the  mes-
       sage 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 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 fprintf(3) system call.

       format  The original format, exactly as passed to the fprintf(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:
	      errno = EINVAL;
	      int result = fprintf(fp, format, ...);
	      if (result < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s
", explain_errno_fprintf(err, fp, format, ...));
		  exit(EXIT_FAILURE);
	      }

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

   explain_message_fprintf
       void explain_message_fprintf(char *message, int message_size, FILE *fp, const char *format, ...);

       The  explain_message_fprintf  function  is  used to obtain an explanation of an error returned by the fprintf(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 fprintf(3) system call.

       format  The original format, exactly as passed to the fprintf(3) system call.

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

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

   explain_message_errno_fprintf
       void explain_message_errno_fprintf(char *message, int message_size, int errnum, FILE *fp, const char *format, ...);

       The explain_message_errno_fprintf function is used to obtain an explanation of an error returned by the fprintf(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  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 fprintf(3) system call.

       format  The original format, exactly as passed to the fprintf(3) system call.

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

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

SEE ALSO

       fprintf(3)
	       formatted output conversion

       explain_fprintf_or_die(3)
	       formatted output conversion and report errors

COPYRIGHT

       libexplain version 0.52
       Copyright (C) 2010 Peter Miller

																explain_fprintf(3)