logread queries the state of the gallery. It prints which employees and
guests are in the gallery or its rooms, and allows for various
time-based queries of the state of the gallery. The following
invocations must be supported:
logread -K <token> -S <log>
logread -K <token> -R (-E <name> | -G <name>) <log>
The following invocations are optional (for extra points). If you do not implement an optional feature, be sure to print unimplemented to standard output when an optional argument is provided.
logread -K <token> -T (-E <name> | -G <name>) <log>
logread -K <token> -I (-E <name> | -G <name>) [(-E <name> | -G <name>) ...] <log>
As per the above invocations, only one of -S, -R, -T, or -I may be specified at once.
In what follows, we refer to employees or visitors who are ‘in the
gallery’. Each person is expected to first enter the gallery (using
logappend option -A) prior to entering any particular room of the
gallery. Once in the gallery, he or she may enter and leave various
rooms (using logappend options -A -R and options -L -R,
respectively). Finally, the person will leave the gallery (using logappend
option -L). During this whole sequence of events, a person is
considered to be ‘in the gallery’. See the examples
for more information.
When output elements are comma-separated lists, there will be no spaces before or after the commas.
-K token Token used to authenticate the log. This token consists of an arbitrary sized string of alphanumeric characters and will be the same between executions of logappend and logread. You may assume the token contains sufficient entropy so that it cannot be guessed in a reasonable amount of time. If the log cannot be
authenticated with the token (i.e., it is not the same token that was used to create the file), then "integrity violation" should be printed to stdout and 255 should be returned.
-S Print the current state of the log to stdout. The state should
be printed to stdout on at least two lines, with lines separated by
the \n (newline) character. The first line should be a
comma-separated list of employees currently in the gallery. The
second line should be a comma-separated list of guests currently in
the gallery. The remaining lines should provide room-by-room
information indicating which guest or employee is in which
room. Each line should begin with a room ID, printed as a decimal
integer, followed by a colon, followed by a space, followed by a
comma-separated list of guests and employees. Room IDs should be
printed in ascending integer order, all guest/employee names should
be printed in ascending lexicographic string order.
-R Give a list of all rooms entered by an employee or guest. Output the list of rooms in chronological order. If this argument is specified, either -E or -G must be specified. The list is printed to stdout in one comma-separated list of room identifiers.
-T Gives the total time spent in the gallery by an employee or guest. If the employee or guest is still in the gallery, print the time spent so far. Output in an integer on a single line. This feature is optional. If the specified employee or guest does not appear in the gallery, then nothing is printed.
-I Prints the rooms, as a comma-separated list of room IDs, that were occupied by all the specified employees and guests at the same time over the complete history of the gallery. Room IDs should be printed in ascending numerical order. This feature is optional. If a specified employee or guest does not appear in the gallery, it is ignored. If no room ever contained all of the specified persons, then nothing is printed.
-E Employee name. May be specified multiple times when used with -I.
-G Guest name. May be specified multiple times when used with -I.
log The name of the file log used for recording events. The filename may be specified with a string of alphanumeric characters (including underscores and periods).
If logread is given an employee or guest name that does not exist in the log, it should print nothing about that employee (which may result in empty output).
If logread cannot validate that an entry in the log was created with an invocation of logappend using a matching token, then logread should return a 255 and print “integrity violation” to stdout.
-I or -T is used to specify an employee who does not exist in the log, print nothing and exit with return 0logread should print “invalid” to stdout and exit, returning a 255.