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explain_fseek(3)	   Library Functions Manual	      explain_fseek(3)

NAME
       explain_fseek - explain fseek(3)	errors

SYNOPSIS
       #include	<libexplain/fseek.h>
       const char *explain_fseek(FILE *fp, long	offset,	int whence);
       const char *explain_errno_fseek(int errnum, FILE	*fp, long offset, int
       whence);
       void explain_message_fseek(char *message, int message_size, FILE	*fp,
       long offset, int	whence);
       void explain_message_errno_fseek(char *message, int message_size, int
       errnum, FILE *fp, long offset, int whence);

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

   explain_fseek
       const char *explain_fseek(FILE *fp, long	offset,	int whence);

       The explain_fseek function is used to obtain an explanation of an error
       returned	by the fseek(3)	system call. The least the message  will  con-
       tain  is	the value of strerror(errno), but usually it will do much bet-
       ter, 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 fseek(3) system call.

       offset  The  original  offset, exactly as passed	to the fseek(3)	system
	       call.

       whence  The original whence, exactly as passed to the  fseek(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 buf-
       fer 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 (fseek(fp, offset, whence) < 0)
	      {
		  fprintf(stderr, "%s\n", explain_fseek(fp, offset, whence));
		  exit(EXIT_FAILURE);
	      }

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

   explain_errno_fseek
       const char *explain_errno_fseek(int errnum, FILE	*fp, long offset, int
       whence);

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

       offset  The original offset, exactly as passed to the  fseek(3)	system
	       call.

       whence  The  original  whence, exactly as passed	to the fseek(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 buf-
       fer 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 (fseek(fp, offset, whence) < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_fseek(err, fp, offset,
		  whence));
		  exit(EXIT_FAILURE);
	      }

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

   explain_message_fseek
       void explain_message_fseek(char *message, int message_size, FILE	*fp,
       long offset, int	whence);

       The  explain_message_fseek function is used to obtain an	explanation of
       an error	returned by the	fseek(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 suit-
	       able message return buffer is supplied, this function is	thread
	       safe.

       message_size
	       The  size  in  bytes  of	the location in	which to store the re-
	       turned message.

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

       offset  The original offset, exactly as passed to the  fseek(3)	system
	       call.

       whence  The  original  whence, exactly as passed	to the fseek(3)	system
	       call.

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

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

   explain_message_errno_fseek
       void explain_message_errno_fseek(char *message, int message_size, int
       errnum, FILE *fp, long offset, int whence);

       The explain_message_errno_fseek function	is used	to obtain an  explana-
       tion  of	 an  error returned by the fseek(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 suit-
	       able message return buffer is supplied, this function is	thread
	       safe.

       message_size
	       The  size  in  bytes  of	the location in	which to store the re-
	       turned 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 fseek(3) system call.

       offset  The original offset, exactly as passed to the  fseek(3)	system
	       call.

       whence  The  original  whence, exactly as passed	to the fseek(3)	system
	       call.

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

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

SEE ALSO
       fseek(3)
	       reposition a stream

       explain_fseek_or_die(3)
	       reposition a stream and report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2010 Peter	Miller

							      explain_fseek(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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