NAME
explain_gethostname - explain gethostname(2) errors
SYNOPSIS
#include <libexplain/gethostname.h>
const char *explain_gethostname(char *data, size_t data_size);
const char *explain_errno_gethostname(int errnum, char *data, size_t
data_size);
void explain_message_gethostname(char *message, int message_size, char
*data, size_t data_size);
void explain_message_errno_gethostname(char *message, int message_size,
int errnum, char *data, size_t data_size);
DESCRIPTION
These functions may be used to obtain explanations for errors returned
by the gethostname(2) system call.
explain_gethostname
const char *explain_gethostname(char *data, size_t data_size);
The explain_gethostname function is used to obtain an explanation of an
error returned by the gethostname(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 (gethostname(data, data_size) < 0)
{
fprintf(stderr, "%s\n", explain_gethostname(data, data_size));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_gethostname_or_die(3) function.
data The original data, exactly as passed to the gethostname(2)
system call.
data_size
The original data_size, exactly as passed to the gethostname(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_gethostname
const char *explain_errno_gethostname(int errnum, char *data, size_t
data_size);
The explain_errno_gethostname function is used to obtain an explanation
of an error returned by the gethostname(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.
This function is intended to be used in a fashion similar to the
following example:
if (gethostname(data, data_size) < 0)
{
int err = errno;
fprintf(stderr, "%s\n", explain_errno_gethostname(err, data, data_size));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_gethostname_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.
data The original data, exactly as passed to the gethostname(2)
system call.
data_size
The original data_size, exactly as passed to the gethostname(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_gethostname
void explain_message_gethostname(char *message, int message_size, char
*data, size_t data_size);
The explain_message_gethostname function is used to obtain an
explanation of an error returned by the gethostname(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 (gethostname(data, data_size) < 0)
{
char message[3000];
explain_message_gethostname(message, sizeof(message), data, data_size);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_gethostname_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.
data The original data, exactly as passed to the gethostname(2)
system call.
data_size
The original data_size, exactly as passed to the gethostname(2)
system call.
explain_message_errno_gethostname
void explain_message_errno_gethostname(char *message, int message_size,
int errnum, char *data, size_t data_size);
The explain_message_errno_gethostname function is used to obtain an
explanation of an error returned by the gethostname(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.
This function is intended to be used in a fashion similar to the
following example:
if (gethostname(data, data_size) < 0)
{
int err = errno;
char message[3000];
explain_message_errno_gethostname(message, sizeof(message), err, data,
data_size);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_gethostname_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.
data The original data, exactly as passed to the gethostname(2)
system call.
data_size
The original data_size, exactly as passed to the gethostname(2)
system call.
SEE ALSO
gethostname(2)
get/set hostname
explain_gethostname_or_die(3)
get/set hostname and report errors
COPYRIGHT
libexplain version 0.19
Copyright (C) 2009 Peter Miller
explain_gethostname(3)