NAME

       explain_lseek - explain lseek(2) errors

SYNOPSIS

       #include <libexplain/lseek.h>
       const char *explain_lseek(int fildes, long long offset, int whence);
       const char *explain_errno_lseek(int errnum, int fildes, long long offset, int whence);
       void  explain_message_lseek(char *message, int message_size, int fildes, long long offset,
       int whence);
       void explain_message_errno_lseek(char *message, int message_size, int errnum, int  fildes,
       long long offset, int whence);

DESCRIPTION

       These functions may be used to obtain explanations for lseek(2) errors.

   explain_lseek
       const char *explain_lseek(int fildes, long long offset, int whence);

       The explain_lseek function may be used to obtain a human readable explanation of what went
       wrong in an lseek(2) 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 (lseek(fd, offset, whence) == (off_t)-1)
              {
                  fprintf(stderr, '%s0, explain_lseek(fd, offset, whence);
                  exit(EXIT_FAILURE);
              }

       fildes  The original fildes, exactly as passed to the lseek(2) system call.

       offset  The original offset, exactly as passed to the lseek(2) system call.

       whence  The original whence, exactly as passed to the lseek(2) 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_lseek
       const char *explain_errno_lseek(int errnum, int fildes, long long offset, int whence);

       The explain_errno_lseek function may be used to obtain a  human  readable  explanation  of
       what  went  wrong  in  an lseek(2) 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 (lseek(fd, offset, whence) == (off_t)-1)
              {
                  int errnum = errno;
                  fprintf(stderr, '%s0, explain_errno_lseek(fd, eernum, offset,
                      whence);
                  exit(EXIT_FAILURE);
              }

       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.

       fildes  The original fildes, exactly as passed to the lseek(2) system call.
               offset The original offset, exactly as passed to the lseek(2) system call.
               whence The original whence, exactly as passed to the lseek(2) 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_lseek
       void explain_message_lseek(char *message, int message_size, int fildes, long long  offset,
       int whence);

       The  explain_message_lseek  function may be used to obtain a human readable explanation of
       what went wrong in an lseek(2) 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 (lseek(fd, offset, whence) == (off_t)-1)
              {
                  char message[3000];
                  explain_message_lseek(message, sizeof(message), fd, offset, whence);
                  fprintf(stderr, '%s0, message);
                  exit(EXIT_FAILURE);
              }

       message The location in which to store the returned message.   Because  a  message  return
               buffer has been supplied, this function is thread safe.

       message_size
               The size in bytes of the location in which to store the returned message.

       fildes  The original fildes, exactly as passed to the lseek(2) system call.

       offset  The original offset, exactly as passed to the lseek(2) system call.

       whence  The original whence, exactly as passed to the lseek(2) system call.

   explain_message_errno_lseek
       void  explain_message_errno_lseek(char *message, int message_size, int errnum, int fildes,
       long long offset, int whence);

       The  explain_message_errno_lseek  function  may  be  used  to  obtain  a  human   readable
       explanation  of  what  went  wrong in an lseek(2) 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 (lseek(fd, offset, whence) == (off_t)-1)
              {
                  char message[3000];
                  int errnum = errno;
                  explain_message_errno_lseek(message, sizeof(message), errnum, fd,
                      offset, whence);
                  fprintf(stderr, '%s0, message);
                  exit(EXIT_FAILURE);
              }

       message The  location  in  which  to store the returned message.  Because a message return
               buffer has been 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.

       fildes  The original fildes, exactly as passed to the lseek(2) system call.

       offset  The orginal offset, exactly as passed to the lseek(2) system call.

       whence  The original whence, exactly as passed to the lseek(2) system call.

COPYRIGHT

       libexplain version 1.4
       Copyright (C) 2008 Peter Miller

AUTHOR

       Written by Peter Miller <pmiller@opensource.org.au>

                                                                                 explain_lseek(3)