libexplain/sethostname.h File Reference

explain sethostname(2) errors More...

#include <libexplain/gcc_attributes.h>
#include <unistd.h>

Go to the source code of this file.

Functions
void	explain_sethostname_or_die (const char *name, size_t name_size)
int	explain_sethostname_on_error (const char *name, size_t name_size) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_sethostname (const char *name, size_t name_size) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_sethostname (int errnum, const char *name, size_t name_size) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_sethostname (char *message, int message_size, const char *name, size_t name_size)
void	explain_message_errno_sethostname (char *message, int message_size, int errnum, const char *name, size_t name_size)

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Detailed Description

explain sethostname(2) errors

Definition in file sethostname.h.

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Function Documentation

const char* explain_errno_sethostname	(	int	errnum,
		const char *	name,
		size_t	name_size
	)

The explain_errno_sethostname function is used to obtain an explanation of an error returned by the sethostname(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 (sethostname(name, name_size) < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_sethostname(err, name,
         name_size));
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_sethostname_or_die function.

Parameters:

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.
name	The original name, exactly as passed to the sethostname(2) system call.
name_size	The original name_size, exactly as passed to the sethostname(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.

void explain_message_errno_sethostname	(	char *	message,
		int	message_size,
		int	errnum,
		const char *	name,
		size_t	name_size
	)

The explain_message_errno_sethostname function is used to obtain an explanation of an error returned by the sethostname(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 (sethostname(name, name_size) < 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_sethostname(message, sizeof(message), err, name,
         name_size);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_sethostname_or_die function.

Parameters:

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.
name	The original name, exactly as passed to the sethostname(2) system call.
name_size	The original name_size, exactly as passed to the sethostname(2) system call.

void explain_message_sethostname	(	char *	message,
		int	message_size,
		const char *	name,
		size_t	name_size
	)

The explain_message_sethostname function is used to obtain an explanation of an error returned by the sethostname(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.

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 (sethostname(name, name_size) < 0)
 {
     char message[3000];
     explain_message_sethostname(message, sizeof(message), name, name_size);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_sethostname_or_die function.

Parameters:

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.
name	The original name, exactly as passed to the sethostname(2) system call.
name_size	The original name_size, exactly as passed to the sethostname(2) system call.

const char* explain_sethostname	(	const char *	name,
		size_t	name_size
	)

The explain_sethostname function is used to obtain an explanation of an error returned by the sethostname(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 (sethostname(name, name_size) < 0)
 {
     fprintf(stderr, "%s\n", explain_sethostname(name, name_size));
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_sethostname_or_die function.

Parameters:

name	The original name, exactly as passed to the sethostname(2) system call.
name_size	The original name_size, exactly as passed to the sethostname(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.

int explain_sethostname_on_error	(	const char *	name,
		size_t	name_size
	)

The explain_sethostname_on_error function is used to call the sethostname(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_sethostname(3) function.

This function is intended to be used in a fashion similar to the following example:

 if (explain_sethostname_on_error(name, name_size) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

Parameters:

name	The name, exactly as to be passed to the sethostname(2) system call.
name_size	The name_size, exactly as to be passed to the sethostname(2) system call.

Returns:

The value returned by the wrapped sethostname(2) system call.

void explain_sethostname_or_die	(	const char *	name,
		size_t	name_size
	)

The explain_sethostname_or_die function is used to call the sethostname(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_sethostname(3) function, and then the process terminates by calling exit(EXIT_FAILURE).

This function is intended to be used in a fashion similar to the following example:

 explain_sethostname_or_die(name, name_size);

Parameters:

name	The name, exactly as to be passed to the sethostname(2) system call.
name_size	The name_size, exactly as to be passed to the sethostname(2) system call.

Returns:

This function only returns on success, see sethostname(2) for more information. On failure, prints an explanation and exits, it does not return.