explain_fcntl

const char *explain_fcntl(int fildes, int command, long arg);

The explain_fcntl function is used to obtain an explanation of an error returned by the fcntl(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 (fcntl(fildes, command, arg) < 0)
{


    fprintf(stderr, "%s\n", explain_fcntl(fildes, command, arg));


    exit(EXIT_FAILURE);
}

fildes

The original fildes, exactly as passed to the fcntl(2) system call.

command

The original command, exactly as passed to the fcntl(2) system call.

arg

The original arg, exactly as passed to the fcntl(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_fcntl

const char *explain_errno_fcntl(int errnum, int fildes, int command, long arg);

The explain_errno_fcntl function is used to obtain an explanation of an error returned by the fcntl(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 (fcntl(fildes, command, arg) < 0)
{


    int err = errno;


    fprintf(stderr, "%s\n", explain_errno_fcntl(err, fildes, command, arg));


    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.

fildes

The original fildes, exactly as passed to the fcntl(2) system call.

command

The original command, exactly as passed to the fcntl(2) system call.

arg

The original arg, exactly as passed to the fcntl(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_fcntl

void explain_message_fcntl(char *message, int message_size, int fildes, int command, long arg);

The explain_message_fcntl function may be used to obtain an explanation of an error returned by the fcntl(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 (fcntl(fildes, command, arg) < 0)
{


    char message[3000];


    explain_message_fcntl(message, sizeof(message), fildes, command, arg);


    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.

fildes

The original fildes, exactly as passed to the fcntl(2) system call.

command

The original command, exactly as passed to the fcntl(2) system call.

arg

The original arg, exactly as passed to the fcntl(2) system call.

explain_message_errno_fcntl

void explain_message_errno_fcntl(char *message, int message_size, int errnum, int fildes, int command, long arg);

The explain_message_errno_fcntl function may be used to obtain an explanation of an error returned by the fcntl(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 (fcntl(fildes, command, arg) < 0)
{


    int err = errno;


    char message[3000];


    explain_message_errno_fcntl(message, sizeof(message), err, fildes,


        command, arg);


    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.

fildes

The original fildes, exactly as passed to the fcntl(2) system call.

command

The original command, exactly as passed to the fcntl(2) system call.

arg

The original arg, exactly as passed to the fcntl(2) system call.