explain_gettimeofday(3)

NAME
explain_gettimeofday - explain gettimeofday(2) errors

SYNOPSIS
#include <libexplain/gettimeofday.h>

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

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

  explain_gettimeofday
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);
    }

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.

  explain_errno_gettimeofday
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);
    }

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.

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

The explain_message_gettimeofday function may be 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)
    {
        char message[3000];
        explain_message_gettimeofday(message, sizeof(message), tv, tz);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

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.

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

The explain_message_errno_gettimeofday function may be 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);
    }

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.

SEE ALSO

gettimeofday(2)
    get time

explain_gettimeofday_or_die(3)
    get time and report errors

COPYRIGHT
libexplain version 1.1
Copyright (C) 2008 Peter Miller