8 /* open/read/write/close */
11 /* Signals handling.. */
17 /** Named pipe used to communicate with process2 */
18 char * read_pipe = "/tmp/process2pipe";
20 /** Descriptor of input pipe */
25 * Shared memory variables
28 * Memory key for processes. Must be same between all processes to properly
33 * Id of the shared memory
38 * Message shared by processes. Contains array of process IDs
44 struct message * processes = NULL;
47 * Message queue variables
55 struct queue_message {
60 void notify_other_processes(int signo) {
62 struct queue_message msg;
66 pid_t pid = processes->pids[i];
68 if (i != 2 && pid != 0) {
70 fprintf(stderr, "[%s] Sending message of type (%d) with value %d\n", "process3", msg.mtype, msg.signo[0]);
71 msgsnd(pid, &msg, sizeof(int), 0);
72 fprintf(stderr, "[%s] Sending signal %s (%d) to PID: %d\n", "process3", strsignal(SIGUSR1), SIGUSR1, pid);
79 * Handler for signals.
81 void sig_handler(int signo)
83 fprintf(stderr, "[%s] Received !\n", "process3");
84 if (signo == SIGUSR1) {
85 fprintf(stderr, "[%s] > Notified!\n", "process3");
86 struct queue_message msg;
87 /* Check queues from both other processes */
88 if (msgrcv(processes->pids[0], &msg, sizeof(int), 3, 0) > 0) {
89 fprintf(stderr, "[%s] > Notified with value: %s!\n", "process3", strsignal(msg.signo[0]));
93 else if (msgrcv(processes->pids[1], &msg, sizeof(int), 3, 0) > 0) {
94 fprintf(stderr, "[%s] > Notified with value: %s!\n", "process3", strsignal(msg.signo[0]));
99 else if (signo == SIGTERM) {
100 fprintf(stderr, "[%s] > Signalling other processes..\n", "process3");
101 processes->pids[2] = 0;
102 notify_other_processes(signo);
104 fprintf(stderr, "[%s] > Releasing resources\n", "process3");
105 close(read_descriptor);
108 else if (signo == SIGTSTP) {
109 fprintf(stderr, "[%s] > Signalling other processes..\n", "process3");
110 notify_other_processes(signo);
112 fprintf(stderr, "[%s] > Closing pipe\n", "process3");
113 close(read_descriptor);
116 else if (signo == SIGCONT) {
117 fprintf(stderr, "[%s] > Signalling other processes..\n", "process3");
118 notify_other_processes(signo);
120 fprintf(stderr, "[%s] > Opening pipe\n", "process3");
121 read_descriptor = open(read_pipe, O_RDONLY);
126 * Program grabs data (calculated number of characters) from process2 and prints
127 * grabbed data to the standard output.
130 /** Buffer used for storing data from input pipe */
133 /** Stores number of bytes read from input pipe in current iteration */
136 fprintf(stderr, "[%s] Init!\n", "process3");
139 * Register signals handled by process
141 if (signal(SIGUSR1, sig_handler) == SIG_ERR) {
142 fprintf(stderr, "can't catch SIGUSR1\n");
144 if (signal(SIGTERM, sig_handler) == SIG_ERR) {
145 fprintf(stderr, "can't catch SIGTERM\n");
147 if (signal(SIGTSTP, sig_handler) == SIG_ERR) {
148 fprintf(stderr, "can't catch SIGTSTP\n");
150 if (signal(SIGCONT, sig_handler) == SIG_ERR) {
151 fprintf(stderr, "can't catch SIGCONT\n");
155 * Register memory to share with other processes, and pass current
156 * process id to the array.
158 shmid = shmget(shmkey, sizeof(struct message), 0666);
160 processes = (struct message *)shmat(shmid, NULL, 0);
161 processes->pids[2] = getpid();
163 fprintf(stderr, "[%s] Shared pid: %d\n", "process3", getpid());
166 * Register message queue to communicate with other processes
169 qid_input = msgget(qkey, IPC_CREAT | 0666);
171 qid_output1 = msgget(processes->pids[1], IPC_CREAT | 0666);
172 qid_output2 = msgget(processes->pids[2], IPC_CREAT | 0666);
174 /* Reading from process2 */
175 read_descriptor = open(read_pipe, O_RDONLY);
178 /* Read data from input pipe */
179 count = read(read_descriptor, &buffer, sizeof(int));
181 fprintf(stderr, "[%s] Fetched: %d bytes\n", "process3", count);
184 fprintf(stderr, "[%s] Process2 send: %d\n", "process3", buffer);
191 /* Release resources in normal program flow exit. */
192 close(read_descriptor);