Write a C++ program called time.c that determines the amount of time necessary to run a command from the command line. T

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Write a C++ program called time.c that
determines the amount of time necessary to run a command from the
command line. This program will be run as "./time <command>"
and will report the amount of elapsed time to run the specified
command. This will involve using fork() and exec() functions, as
well as the gettimeofday() function to determine the elapsed time.
It will also require the use of two different IPC
mechanisms.
The general strategy is to fork a child process that will execute
the specified command. However, before the child executes the
command, it will record a timestamp of the current time (which we
term “starting time”). The parent process will wait for the child
process to terminate.
Once the child terminates, the parent will record the current
timestamp for the ending time. The difference between the starting
and ending times represents the elapsed time to execute the
command. The example output below reports the amount of time to run
the command ls :
./time ls
time ls
Elapsed time: 0.25422
As the parent and child are separate processes, they will need to
arrange how the starting time will be shared between them. You
will
write two versions of this program, each representing a different
method of IPC.
The first version will have the child process write the starting
time to a region of shared memory before it calls exec(). After the
child process terminates, the parent will read the starting time
from shared memory.
Refer to Section 3.7.1 for details using POSIX shared memory. In
that section, there are separate programs for the producer and
consumer. As the solution to this problem requires only a single
program, the region of shared memory can be established before the
child process is forked,
allowing both the parent and child processes access to the region
of shared memory.
The second version will use a pipe. The child will write the
starting time to the pipe, and the parent will read from it
following the termination of the child process.
You will use the gettimeofday() function to record the current
timestamp. This function is passed a pointer to a struct
timeval
object, which contains two members: tv sec and t usec. These
represent the number of elapsed seconds and microseconds since
January 1, 1970 (known as the UNIX EPOCH). The following code
sample illustrates how this function can be used:
struct timeval current;
gettimeofday(&current,NULL);
// current.tv sec represents seconds
// current.tv usec represents microseconds
For IPC between the child and parent processes, the contents of the
shared memory pointer can be assigned the struct timeval
repre-
senting the starting time. When pipes are used, a pointer to a
struct timeval can be written to—and read from—the pipe.