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server.c
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server.c
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#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#define SEM_KEY 9979
#define SHM_KEY 9979
int main(void) {
int shmid, semid, buf, RESULT_FIFO;
char *fifo = "/tmp/RESULT_FIFO";
fd_set readCheck;
// Create a Sem
semid = semget(SEM_KEY, 1, IPC_CREAT | 0644);
if (semid < 0) {
perror("semget");
exit(EXIT_FAILURE);
}
// Allocate a SHM
shmid = shmget(SHM_KEY, sizeof(int), IPC_CREAT | 0660); // IPC_EXCL
if (shmid < 0) {
perror("shmget");
exit(EXIT_FAILURE);
}
// Attach a SHM
int *data = (int *)shmat(shmid, NULL, 0); // SHM_WRONLY
if (*data == -1) {
perror("shmat");
exit(EXIT_FAILURE);
}
// Write to the SHM
*data = 0;
// remove if exists
unlink(fifo);
// Create named FIFO
if (mkfifo(fifo, 0666) == -1) {
perror("mkfifo");
return EXIT_FAILURE;
}
// Open FIFO
RESULT_FIFO = open(fifo, O_RDONLY);
// Read from FIFO and print the content to stdout
FD_ZERO(&readCheck);
FD_SET(RESULT_FIFO, &readCheck);
if (select(RESULT_FIFO + 1, &readCheck, NULL, NULL, NULL) < 0) {
perror("select");
return EXIT_SUCCESS;
}
// Read only when a msg is avalible
if (FD_ISSET(RESULT_FIFO, &readCheck)) {
if (read(RESULT_FIFO, &buf, sizeof(buf)) != -1)
fprintf(stdout, "Received %d from RESULT_FIFO\n", buf);
}
// Close File Descriptor and remove fifo
close(RESULT_FIFO);
unlink(fifo);
// remove SHM
if (shmctl(shmid, IPC_RMID, NULL) < 0) perror("shmctl");
if (semctl(semid, 0, IPC_RMID) < 0) perror("semctl");
return EXIT_SUCCESS;
}