explain_lseek(3)

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, '%s, 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, '%s, 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, '%s, 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, '%s, 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 1.2
Copyright (C) 2008 Peter Miller

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