Provided by: libexplain-dev_1.4.D001-7_amd64 
NAME
explain_getsockopt - explain getsockopt(2) errors
SYNOPSIS
#include <libexplain/getsockopt.h>
const char *explain_getsockopt(int fildes, int level, int name, void *data, socklen_t *data_size);
const char *explain_errno_getsockopt(int errnum, int fildes, int level, int name, void *data, socklen_t
*data_size);
void explain_message_getsockopt(char *message, int message_size, int fildes, int level, int name, void
*data, socklen_t *data_size);
void explain_message_errno_getsockopt(char *message, int message_size, int errnum, int fildes, int level,
int name, void *data, socklen_t *data_size);
DESCRIPTION
These functions may be used to obtain explanations for errors returned by the getsockopt(2) system call.
explain_getsockopt
const char *explain_getsockopt(int fildes, int level, int name, void *data, socklen_t *data_size);
The explain_getsockopt function is used to obtain an explanation of an error returned by the
getsockopt(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 (getsockopt(fildes, level, name, data, data_size) < 0)
{
fprintf(stderr, "%s\n", explain_getsockopt(fildes,
level, name, data, data_size));
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the explain_getsockopt_or_die(3) function.
fildes The original fildes, exactly as passed to the getsockopt(2) system call.
level The original level, exactly as passed to the getsockopt(2) system call.
name The original name, exactly as passed to the getsockopt(2) system call.
data The original data, exactly as passed to the getsockopt(2) system call.
data_size
The original data_size, exactly as passed to the getsockopt(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_getsockopt
const char *explain_errno_getsockopt(int errnum, int fildes, int level, int name, void *data, socklen_t
*data_size);
The explain_errno_getsockopt function is used to obtain an explanation of an error returned by the
getsockopt(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 (getsockopt(fildes, level, name, data, data_size) < 0)
{
int err = errno;
fprintf(stderr, "%s\n", explain_errno_getsockopt(err,
fildes, level, name, data, data_size));
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the explain_getsockopt_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 getsockopt(2) system call.
level The original level, exactly as passed to the getsockopt(2) system call.
name The original name, exactly as passed to the getsockopt(2) system call.
data The original data, exactly as passed to the getsockopt(2) system call.
data_size
The original data_size, exactly as passed to the getsockopt(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_getsockopt
void explain_message_getsockopt(char *message, int message_size, int fildes, int level, int name, void
*data, socklen_t *data_size);
The explain_message_getsockopt function may be used to obtain an explanation of an error returned by the
getsockopt(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 (getsockopt(fildes, level, name, data, data_size) < 0)
{
char message[3000];
explain_message_getsockopt(message, sizeof(message),
fildes, level, name, data, data_size);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the explain_getsockopt_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 getsockopt(2) system call.
level The original level, exactly as passed to the getsockopt(2) system call.
name The original name, exactly as passed to the getsockopt(2) system call.
data The original data, exactly as passed to the getsockopt(2) system call.
data_size
The original data_size, exactly as passed to the getsockopt(2) system call.
explain_message_errno_getsockopt
void explain_message_errno_getsockopt(char *message, int message_size, int errnum, int fildes, int level,
int name, void *data, socklen_t *data_size);
The explain_message_errno_getsockopt function may be used to obtain an explanation of an error returned
by the getsockopt(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 (getsockopt(fildes, level, name, data, data_size) < 0)
{
int err = errno;
char message[3000];
explain_message_errno_getsockopt(message, sizeof(message),
err, fildes, level, name, data, data_size);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the explain_getsockopt_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 getsockopt(2) system call.
level The original level, exactly as passed to the getsockopt(2) system call.
name The original name, exactly as passed to the getsockopt(2) system call.
data The original data, exactly as passed to the getsockopt(2) system call.
data_size
The original data_size, exactly as passed to the getsockopt(2) system call.
SEE ALSO
getsockopt(2)
get and set options on sockets
explain_getsockopt_or_die(3)
get and set options on sockets and report errors
COPYRIGHT
libexplain version 1.4
Copyright (C) 2009 Peter Miller
explain_getsockopt(3)