libexplain/ustat.h File Reference

explain ustat(2) errors More...

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

Go to the source code of this file.

Functions
void	explain_ustat_or_die (dev_t dev, struct ustat *data)
int	explain_ustat_on_error (dev_t dev, struct ustat *data)
const char *	explain_ustat (dev_t dev, struct ustat *data) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_ustat (int errnum, dev_t dev, struct ustat *data) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_ustat (char *message, int message_size, dev_t dev, struct ustat *data)
void	explain_message_errno_ustat (char *message, int message_size, int errnum, dev_t dev, struct ustat *data)

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Detailed Description

explain ustat(2) errors

These functions may be used to obtain explanations for errors returned by the ustat(2) system call.

Definition in file ustat.h.

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Function Documentation

const char* explain_errno_ustat	(	int	errnum,
		dev_t	dev,
		struct ustat *	data
	)

The explain_errno_ustat function is used to obtain an explanation of an error returned by the ustat(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.

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.
dev	The original dev, exactly as passed to the ustat(2) system call.
data	The original data, exactly as passed to the ustat(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.

Example:

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

 if (ustat(dev, data) < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_ustat(err, dev, data));
     exit(EXIT_FAILURE);
 }

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

void explain_message_errno_ustat	(	char *	message,
		int	message_size,
		int	errnum,
		dev_t	dev,
		struct ustat *	data
	)

The explain_message_errno_ustat function is used to obtain an explanation of an error returned by the ustat(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.

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.
dev	The original dev, exactly as passed to the ustat(2) system call.
data	The original data, exactly as passed to the ustat(2) system call.

Example:

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

 if (ustat(dev, data) < 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_ustat(message, sizeof(message), err, dev, data);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

void explain_message_ustat	(	char *	message,
		int	message_size,
		dev_t	dev,
		struct ustat *	data
	)

The explain_message_ustat function is used to obtain an explanation of an error returned by the ustat(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.

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.
dev	The original dev, exactly as passed to the ustat(2) system call.
data	The original data, exactly as passed to the ustat(2) system call.

Example:

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

 if (ustat(dev, data) < 0)
 {
     char message[3000];
     explain_message_ustat(message, sizeof(message), dev, data);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

const char* explain_ustat	(	dev_t	dev,
		struct ustat *	data
	)

The explain_ustat function is used to obtain an explanation of an error returned by the ustat(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.

Parameters:

dev	The original dev, exactly as passed to the ustat(2) system call.
data	The original data, exactly as passed to the ustat(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.

Example:

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

 if (ustat(dev, data) < 0)
 {
     fprintf(stderr, "%s\n", explain_ustat(dev, data));
     exit(EXIT_FAILURE);
 }

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

int explain_ustat_on_error	(	dev_t	dev,
		struct ustat *	data
	)

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

Parameters:

dev	The dev, exactly as to be passed to the ustat(2) system call.
data	The data, exactly as to be passed to the ustat(2) system call.

Returns:

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

Example:

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

 if (explain_ustat_on_error(dev, data) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

void explain_ustat_or_die	(	dev_t	dev,
		struct ustat *	data
	)

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

Parameters:

dev	The dev, exactly as to be passed to the ustat(2) system call.
data	The data, exactly as to be passed to the ustat(2) system call.

Returns:

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

Example:

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

 explain_ustat_or_die(dev, data);