explain_fclose

The explain_fclose function is used to obtain an explanation of an error returned by the fclose(3) function. 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 (fclose(fp))
{
    fprintf(stderr, "%s\n", explain_fclose(fp));
    exit(EXIT_FAILURE);
}

fp

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

Note: This function may be of little diagnostic value, because libc may have destroyed any useful context, leaving nothing for libexplain to work with (this is true of glibc in particular). For files that are open for writing, you will obtain more useful information by first calling fflush(3), as in the following example

if (fflush(fp))
{
    fprintf(stderr, "%s\n", explain_fflush(fp));
    exit(EXIT_FAILURE);
}
if (fclose(fp))
{
    fprintf(stderr, "%s\n", explain_fclose(fp));
    exit(EXIT_FAILURE);
}

explain_errno_fclose

The explain_errno_fclose function is used to obtain an explanation of an error returned by the fclose(3) function. 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 (fclose(fp))
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_fclose(err, fp));
    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.

fp

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

Note: This function may be of little diagnostic value, because libc may have destroyed any useful context, leaving nothing for libexplain to work with (this is true of glibc in particular). For files that are open for writing, you will obtain more useful information by first calling fflush(3), as in the following example

if (fflush(fp))
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_fflush(err, fp));
    exit(EXIT_FAILURE);
}
if (fclose(fp))
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_fclose(err, fp));
    exit(EXIT_FAILURE);
}

explain_message_fclose

The explain_message_fclose function is used to obtain an explanation of an error returned by the fclose(3) function. 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 (fclose(fp))
{
    char message[3000];
    explain_message_fclose(message, sizeof(message), fp);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

message

The location in which to store the returned message. Because a message return buffer has been 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 fclose(3) system call.

Note: This function may be of little diagnostic value, because libc may have destroyed any useful context, leaving nothing for libexplain to work with (this is true of glibc in particular). For files that are open for writing, you will obtain more useful information by first calling fflush(3), as in the following example

if (fflush(fp))
{
    char message[3000];
    explain_message_fflush(message, sizeof(message), fp);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}
if (fclose(fp))
{
    char message[3000];
    explain_message_fclose(message, sizeof(message), fp);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

explain_message_errno_fclose

The explain_message_errno_fclose function is used to obtain an explanation of an error returned by the fclose(3) function. 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 exameple:

if (fclose(fp))
{
    int err = errno;
    char message[3000];
    explain_message_errno_fclose(message, sizeof(message),
        err, fp);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

message

The location in which to store the returned message. Because a message return buffer has been 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 fclose(3) system call.

Note: This function may be of little diagnostic value, because libc may have destroyed any useful context, leaving nothing for libexplain to work with (this is true of glibc in particular). For files that are open for writing, you will obtain more useful information by first calling fflush(3), as in the following example

if (fflush(fp))
{
    int err = errno;
    char message[3000];
    explain_message_errno_fflush(message, sizeof(message),
        err, fp);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}
if (fclose(fp))
{
    int err = errno;
    char message[3000];
    explain_message_errno_fclose(message, sizeof(message),
        err, fp);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}