Provided by: libexplain-dev_1.4.D001-8_amd64 bug

NAME

       explain_ftell - explain ftell(3) errors

SYNOPSIS

       #include <libexplain/ftell.h>
       const char *explain_ftell(FILE *fp);
       const char *explain_errno_ftell(int errnum, FILE *fp);
       void explain_message_ftell(char *message, int message_size, FILE *fp);
       void explain_message_errno_ftell(char *message, int message_size, int errnum, FILE *fp);

DESCRIPTION

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

   explain_ftell
       const char *explain_ftell(FILE *fp);

       The explain_ftell function is used to obtain an explanation of an error  returned  by  the
       ftell(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 ftell(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:
              long result = ftell(fp);
              if (result < 0)
              {
                  fprintf(stderr, "%s\n", explain_ftell(fp));
                  exit(EXIT_FAILURE);
              }

       The above code example is available pre‐packaged as the explain_ftell_or_die(3) function.

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

       The  explain_errno_ftell function is used to obtain an explanation of an error returned by
       the  ftell(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 ftell(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:
              long result = ftell(fp);
              if (result < 0)
              {
                  int err = errno;
                  fprintf(stderr, "%s\n", explain_errno_ftell(err, fp));
                  exit(EXIT_FAILURE);
              }

       The above code example is available pre‐packaged as the explain_ftell_or_die(3) function.

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

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

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

       The above code example is available pre‐packaged as the explain_ftell_or_die(3) function.

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

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

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

       The above code example is available pre‐packaged as the explain_ftell_or_die(3) function.

SEE ALSO

       ftell(3)
               reposition a stream

       explain_ftell_or_die(3)
               reposition a stream and report errors

COPYRIGHT

       libexplain version 1.4
       Copyright (C) 2010 Peter Miller

                                                                                 explain_ftell(3)