explain_lseek

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

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

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

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.