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
Copyright (C) 2008 Peter Miller
AUTHOR
Written by Peter Miller <pmiller@opensource.org.au>
explain_lseek(3)