explain_ferror

The explain_ferror function is used to obtain an explanation of an error returned by the ferror(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.

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

if (ferror(fp) < 0)
{
    fprintf(stderr, "%s\n", explain_ferror(fp));
    exit(EXIT_FAILURE);
}

It is essential that this function cal be placed as close as possible to the I/O code that has caused the problem, otherwise intervening code could have altered the errno global variable.

fp

The original fp, exactly as passed to the ferror(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.

explain_errno_ferror

The explain_errno_ferror function is used to obtain an explanation of an error returned by the ferror(3) 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 (ferror(fp) < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_ferror(err, fp));
    exit(EXIT_FAILURE);
}

It is essential that this function cal be placed as close as possible to the I/O code that has caused the problem, otherwise intervening code could have altered the errno global variable.

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.

fp

The original fp, exactly as passed to the ferror(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.

explain_message_ferror

The explain_message_ferror function may be used to obtain an explanation of an error returned by the ferror(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.

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

if (ferror(fp) < 0)
{
    char message[3000];
    explain_message_ferror(message, sizeof(message), fp);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

It is essential that this function cal be placed as close as possible to the I/O code that has caused the problem, otherwise intervening code could have altered the errno global variable.

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.

fp

The original fp, exactly as passed to the ferror(3) system call.

explain_message_errno_ferror

The explain_message_errno_ferror function may be used to obtain an explanation of an error returned by the ferror(3) 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 (ferror(fp) < 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_ferror(message, sizeof(message), err, fp);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

It is essential that this function cal be placed as close as possible to the I/O code that has caused the problem, otherwise intervening code could have altered the errno global variable.

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.

fp

The original fp, exactly as passed to the ferror(3) system call.