For this assignment, you will implement something that looks a lot
like a print spooler.  

The print spooler itself will run as some other userid.  You must
test it as one or more other users.

Briefly, you must implement three commands, "addqueue", "showqueue",
and "rmqueue".  All are privileged.  "addqueue' takes a set of file
names as arguments, and copies the contents of those files to some
protected directory.  "showqueue" lists the queued files: some
arbitrary name (*not* the original file name, but a number is fine),
the owner (the userid who made the request), the time and date it
was added, and some sort of unique identifier.  This unique identifier
may or may not be the same as the file name; that's entirely up to
you.  "rmqueue" takes a list of unique identifiers and deletes those
entries from the queue.  Only the user who added a file to the queue
may delete it.

You do not need to worry about race conditions for generating file
names or unique identifiers.  That is, there is no need to lock any
resource for the counter.

You may use setuid or message-passing.  If you use the latter, it's
perfectly ok to start some daemons manually.

You must use at least three userids: one for the protected resource,
and at least two test userids.  That latter is needed to test if
one user can delete the other's files.

There must not be any way to look at or change the spool directory
or its contents except through these commands.

----
Output Format:

1. addqueue
In case of error, return filename, colon and one space and the error message.

$ addqueue file1 file2 file3                                                    

$ addqueue file4 file5
file4: error message
 
2. showqueue
One line for each file and one tab between each detail. It should be sorted by date and time it was added. If there is nothing in the queue, nothing need to be shown. You are welcome to use userid or username for the owner field.
 
$ showqueue                                                                     
arbitrary_file_name_1 1000 2016-09-28_13:33 fileid01
arbitrary_file_name_2  1000  2016-09-28_13:33   fileid02
arbitrary_file_name_3  1000  2015-09-28_13:34   fileid03
arbitrary_file_name_4  1001  2015-09-28_13:52   fileid05

Here, arbitrary_file_name_1/2/3/4 is the name you give to your file and is not a format that you have to follow.
 
3. showqueue
Similar to add queue, in case of error, put filename, colon, one space and the error message.                                                                         
$ rmqueue fileid01
 
$ rmqueue fileid05 fileid04                                                             
fileid04: error_message