explain_open(const char *pathname, int flags, int mode);

The explain_open function is used to obtain an explanation of an error returned by the open(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:

int fd = open(pathname, flags, mode);
if (fd < 0)
{
    fprintf(stderr, '%s0, explain_open(pathname, flags, mode));
    exit(EXIT_FAILURE);
}

pathname

The original pathname, exactly as passed to the open(2) system call.

flags

The original flags, exactly as passed to the open(2) system call.

mode

The original mode, exactly as passed to the open(2) system call (or zero if the original call didn't need a mode argument).

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_open

The explain_errno_open function is used to obtain an explanation of an error returned by the open(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:

int fd = open(pathname, flags, mode);
if (fd < 0)
{
    int err = errno;
    fprintf(stderr, '%s0, explain_errno_open(err, pathname,
        flags, mode));
    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.

pathname

The original pathname, exactly as passed to the open(2) system call.

flags

The original flags, exactly as passed to the open(2) system call.

mode

The original mode, exactly as passed to the open(2) system call (or zero if the original call didn't need a mode argument).

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_open

The explain_message_open function is used to obtain an explanation of an error returned by the open(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:

int fd = open(pathname, flags, mode);
if (fd < 0)
{
    char message[3000];
    explain_message_open(message, sizeof(message), pathname, flags,
        mode);
    fprintf(stderr, '%s0, 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.

pathname

The original pathname, exactly as passed to the open(2) system call.

flags

The original flags, exactly as passed to the open(2) system call.

mode

The original mode, exactly as passed to the open(2) system call (or zero if the original call didn't need a mode argument).

explain_message_errno_open

The explain_message_errno_open function is used to obtain an explanation of an error returned by the open(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 exameple:

int fd = open(pathname, flags, mode);
if (fd < 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_open(message, sizeof(message), err, pathname,
        flags, mode);
    fprintf(stderr, '%s0, 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.

pathname

The original pathname, exactly as passed to the open(2) system call.

flags

The original flags, exactly as passed to the open(2) system call.

mode

The original mode, exactly as passed to the open(2) system call (or zero if the original call didn't need a mode argument).