Description
ADDITION of semaphores and corrected file naming.
It appears file locking does not work well in Mint. Therefore,
you are allowed to use a semaphore (system V or Posix) to protect
each producer’s critical section:
output = fopen(“./output2.txt”, “w”);
fprintf(output, “%d\n”, i);
fclose(output);
ADDITION of semaphores and corrected file naming.
—————————————————————
You have 3 processes running that are producing data by writing
that data to 3 separate files. In our case, the source for the
test processes are provided below. Note that each process
produces data at a different rate.
/************************************************/
/* Produces an even value once every second. */
/************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
int main(void) {
int i;
char number;
FILE *output;
while (1) {
for (i = 0; i < 10; i+=2) {
output = fopen(“./output1.txt”, “w”);
fprintf(output, “%d\n”, i);
fclose(output);
sleep(1);
}
}
return 1;
}
/************************************************/
/* Produces an odd value once every 30 seconds. */
/************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
int main(void) {
int i;
char number;
FILE *output;
while (1) {
for (i = 1; i < 10; i+=2) {
output = fopen(“./output2.txt”, “w”);
fprintf(output, “%d\n”, i);
fclose(output);
sleep(30);
}
}
return 1;
}
/************************************************/
/* Produces a character once every 120 seconds. */
/************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
int main(void) {
int i;
char number;
FILE *output;
while (1) {
for (i = 58; i < 127; i++) {
output = fopen(“./output3.txt”, “w”);
fprintf(output, “%c\n”, i);
fclose(output);
sleep(120);
}
}
return 1;
}
Your job is to create a fourth program that samples the 3 output
files at 0.5 second intervals (the Nyquist sample rate – ie twice
the highest production rate) and produces a new output (output4.txt)
that is a combination of the 3 data streams. There are several
problems, however:
1. You MUST use separate detached p_threads (in the fourth program)
to monitor the 3 producers’ output files and you MUST assume that on
occasion any output file may be unreadable as it is being written
to by the producer (PS This is why we sample at twice the production
rate). You will want to check for locked files, in fact, doing so is
a poor man’s semaphore.
2. You must compile the resulting data such that it appears in order
(data from output1.txt, data from output2.txt, and data from output3.txt)
and write that data to output4.txt such that a history of all data
generated is provided in output4.txt (ie output4.txt cannot just contain
the most recent datasets). In addition, output4.txt cannot contain more
than two consecutive duplicated data (the Nyquist sampling could produce
two consecutive duplicated data). You may want to use mutexes to manage
this.
Notes:
——
1) Only the contents of the three producers will change when we
test your code. The data generation rate and output filenames
will remain the same.
2) Once you start your threads you cannot control them with pthread_join.
REQUIREMENTS:
————-
1. Your program must run on Linux Mint in Leonard 110 or 112.
2. Your full name must appear as a comment at the beginning of your
program.
3. Your tarball must be named hw9-yourname.tar
