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explain_vsprintf

explain_vsprintf

Section: C Library Functions (3)
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NAME

explain_vsprintf - explain vsprintf(3) errors  

SYNOPSIS

#include <libexplain/vsprintf.h>

const char *explain_vsprintf(char *data, const char *format, va_list ap);
const char *explain_errno_vsprintf(int errnum, char *data, const char *format, va_list ap);
void explain_message_vsprintf(char *message, int message_size, char *data, const char *format, va_list ap);
void explain_message_errno_vsprintf(char *message, int message_size, int errnum, char *data, const char *format, va_list ap);  

DESCRIPTION

These functions may be used to obtain explanations for errors returned by the vsprintf(3) system call.  

explain_vsprintf

const char *explain_vsprintf(char *data, const char *format, va_list ap);

The explain_vsprintf function is used to obtain an explanation of an error returned by the vsprintf(3) 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.

data
The original data, exactly as passed to the vsprintf(3) system call.
format
The original format, exactly as passed to the vsprintf(3) system call.
ap
The original ap, exactly as passed to the vsprintf(3) 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:

errno = 0; int result = vsprintf(data, format, ap);
if (result < 0 && errno != 0)
{
fprintf(stderr, "%s\n", explain_vsprintf(data, format, ap));
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_vsprintf_or_die(3) function.  

explain_errno_vsprintf

const char *explain_errno_vsprintf(int errnum, char *data, const char *format, va_list ap);

The explain_errno_vsprintf function is used to obtain an explanation of an error returned by the vsprintf(3) 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.

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 vsprintf(3) system call.
format
The original format, exactly as passed to the vsprintf(3) system call.
ap
The original ap, exactly as passed to the vsprintf(3) 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:

errno = 0; int result = vsprintf(data, format, ap);
if (result < 0 && errno != 0)
{
    int err = errno;
fprintf(stderr, "%s\n", explain_errno_vsprintf(err, data, format, ap));
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_vsprintf_or_die(3) function.  

explain_message_vsprintf

void explain_message_vsprintf(char *message, int message_size, char *data, const char *format, va_list ap);

The explain_message_vsprintf function is used to obtain an explanation of an error returned by the vsprintf(3) 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.

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 vsprintf(3) system call.
format
The original format, exactly as passed to the vsprintf(3) system call.
ap
The original ap, exactly as passed to the vsprintf(3) system call.

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

errno = 0; int result = vsprintf(data, format, ap);
if (result < 0 && errno != 0)
{
    char message[3000];
explain_message_vsprintf(message, sizeof(message), data, format, ap);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_vsprintf_or_die(3) function.  

explain_message_errno_vsprintf

void explain_message_errno_vsprintf(char *message, int message_size, int errnum, char *data, const char *format, va_list ap);

The explain_message_errno_vsprintf function is used to obtain an explanation of an error returned by the vsprintf(3) 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.

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 vsprintf(3) system call.
format
The original format, exactly as passed to the vsprintf(3) system call.
ap
The original ap, exactly as passed to the vsprintf(3) system call.

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

errno = 0; int result = vsprintf(data, format, ap);
if (result < 0 && errno != 0)
{
    int err = errno;
    char message[3000];
explain_message_errno_vsprintf(message, sizeof(message), err, data, format, ap);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_vsprintf_or_die(3) function.  

SEE ALSO

vsprintf(3)
formatted output conversion
explain_vsprintf_or_die(3)
formatted output conversion and report errors
 

COPYRIGHT

libexplain version 0.37
Copyright (C) 2010 Peter Miller


 

Index

NAME
SYNOPSIS
DESCRIPTION
explain_vsprintf
explain_errno_vsprintf
explain_message_vsprintf
explain_message_errno_vsprintf
SEE ALSO
COPYRIGHT

This document was created by man2html, using the manual pages.
Time: 21:45:53 GMT, April 16, 2011