libexplain/gettimeofday.h File Reference

explain gettimeofday(2) errors More...

#include <libexplain/gcc_attributes.h>

Go to the source code of this file.

Functions
void	explain_gettimeofday_or_die (struct timeval *tv, struct timezone *tz)
int	explain_gettimeofday_on_error (struct timeval *tv, struct timezone *tz) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_gettimeofday (struct timeval *tv, struct timezone *tz) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_gettimeofday (int errnum, struct timeval *tv, struct timezone *tz) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_gettimeofday (char *message, int message_size, struct timeval *tv, struct timezone *tz)
void	explain_message_errno_gettimeofday (char *message, int message_size, int errnum, struct timeval *tv, struct timezone *tz)

---

Detailed Description

explain gettimeofday(2) errors

Definition in file gettimeofday.h.

---

Function Documentation

const char* explain_errno_gettimeofday	(	int	errnum,
		struct timeval *	tv,
		struct timezone *	tz
	)

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

The above code example is available pre-packaged as the explain_gettimeofday_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.
tv	The original tv, exactly as passed to the gettimeofday(2) system call.
tz	The original tz, exactly as passed to the gettimeofday(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.

const char* explain_gettimeofday	(	struct timeval *	tv,
		struct timezone *	tz
	)

The explain_gettimeofday function is used to obtain an explanation of an error returned by the gettimeofday(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 (gettimeofday(tv, tz) < 0)
 {
     fprintf(stderr, "%s\n", explain_gettimeofday(tv, tz));
     exit(EXIT_FAILURE);
 }

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

Parameters:

tv	The original tv, exactly as passed to the gettimeofday(2) system call.
tz	The original tz, exactly as passed to the gettimeofday(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_gettimeofday_on_error	(	struct timeval *	tv,
		struct timezone *	tz
	)

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

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

 if (explain_gettimeofday_on_error(tv, tz) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

Parameters:

tv	The tv, exactly as to be passed to the gettimeofday(2) system call.
tz	The tz, exactly as to be passed to the gettimeofday(2) system call.

Returns:

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

void explain_gettimeofday_or_die	(	struct timeval *	tv,
		struct timezone *	tz
	)

The explain_gettimeofday_or_die function is used to call the gettimeofday(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_gettimeofday(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_gettimeofday_or_die(tv, tz);

Parameters:

tv	The tv, exactly as to be passed to the gettimeofday(2) system call.
tz	The tz, exactly as to be passed to the gettimeofday(2) system call.

Returns:

This function only returns on success. On failure, prints an explanation and exits, it does not return.

void explain_message_errno_gettimeofday	(	char *	message,
		int	message_size,
		int	errnum,
		struct timeval *	tv,
		struct timezone *	tz
	)

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

The above code example is available pre-packaged as the explain_gettimeofday_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.
tv	The original tv, exactly as passed to the gettimeofday(2) system call.
tz	The original tz, exactly as passed to the gettimeofday(2) system call.

void explain_message_gettimeofday	(	char *	message,
		int	message_size,
		struct timeval *	tv,
		struct timezone *	tz
	)

The explain_message_gettimeofday function is used to obtain an explanation of an error returned by the gettimeofday(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 (gettimeofday(tv, tz) < 0)
 {
     char message[3000];
     explain_message_gettimeofday(message, sizeof(message), tv, tz);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_gettimeofday_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.
tv	The original tv, exactly as passed to the gettimeofday(2) system call.
tz	The original tz, exactly as passed to the gettimeofday(2) system call.