NAME¶
explain_ioctl - explain
ioctl(2) errors
SYNOPSIS¶
#include <libexplain/ioctl.h>
const char *explain_ioctl(int fildes, int request, void *data);
const char *explain_errno_ioctl(int errnum, int fildes, int request, void
*data);
void explain_message_ioctl(char *message, int message_size, int fildes, int
request, void *data);
void explain_message_errno_ioctl(char *message, int message_size, int errnum,
int fildes, int request, void *data);
DESCRIPTION¶
These functions may be used to obtain explanations for errors returned by the
ioctl(2) system call.
explain_ioctl¶
const char *explain_ioctl(int fildes, int request, void *data);
The
explain_ioctl function is used to obtain an explanation of an error
returned by the
ioctl(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:
int result = ioctl(fildes, request, data);
if (result < 0)
{
fprintf(stderr, "%s\n", explain_ioctl(fildes, request, data));
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the
explain_ioctl_or_die(3) function.
- fildes
- The original fildes, exactly as passed to the
ioctl(2) system call.
- request
- The original request, exactly as passed to the
ioctl(2) system call.
- data
- The original data, exactly as passed to the ioctl(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_ioctl¶
const char *explain_errno_ioctl(int errnum, int fildes, int request, void
*data);
The
explain_errno_ioctl function is used to obtain an explanation of an
error returned by the
ioctl(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 (ioctl(fildes, request, data) < 0)
{
int err = errno;
fprintf(stderr, "%s\n",
explain_errno_ioctl(err, fildes, request, data));
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the
explain_ioctl_or_die(3) function.
- 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
ioctl(2) system call.
- request
- The original request, exactly as passed to the
ioctl(2) system call.
- data
- The original data, exactly as passed to the ioctl(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_ioctl¶
void explain_message_ioctl(char *message, int message_size, int fildes, int
request, void *data);
The
explain_message_ioctl function may be used to obtain an explanation
of an error returned by the
ioctl(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 (ioctl(fildes, request, data) < 0)
{
char message[3000];
explain_message_ioctl(message, sizeof(message), fildes, request, data);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the
explain_ioctl_or_die(3) function.
- 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.
- fildes
- The original fildes, exactly as passed to the
ioctl(2) system call.
- request
- The original request, exactly as passed to the
ioctl(2) system call.
- data
- The original data, exactly as passed to the ioctl(2)
system call.
explain_message_errno_ioctl¶
void explain_message_errno_ioctl(char *message, int message_size, int errnum,
int fildes, int request, void *data);
The
explain_message_errno_ioctl function may be used to obtain an
explanation of an error returned by the
ioctl(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 (ioctl(fildes, request, data) < 0)
{
int err = errno;
char message[3000];
explain_message_errno_ioctl(message, sizeof(message), err,
fildes, request, data);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the
explain_ioctl_or_die(3) function.
- 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.
- fildes
- The original fildes, exactly as passed to the
ioctl(2) system call.
- request
- The original request, exactly as passed to the
ioctl(2) system call.
- data
- The original data, exactly as passed to the ioctl(2)
system call.
SEE ALSO¶
- ioctl(2)
- control device
- explain_ioctl_or_die(3)
- control device and report errors
COPYRIGHT¶
libexplain version 0.52
Copyright (C) 2008 Peter Miller