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
52 struct queue_message {
57 void notify_other_processes(int signo) {
59 struct queue_message msg;
63 pid_t pid = processes->pids[i];
65 if (i != 2 && pid != 0) {
67 fprintf(stderr, "[%s] Sending message of type (%d) with value %d\n", "process3", msg.mtype, msg.signo[0]);
68 msgsnd(qid, &msg, sizeof(int), 0);
69 fprintf(stderr, "[%s] Sending signal %s (%d) to PID: %d\n", "process3", strsignal(SIGUSR1), SIGUSR1, pid);
76 * Handler for signals.
78 void sig_handler(int signo)
80 fprintf(stderr, "[%s] Received %s!\n", "process3", strsignal(signo));
81 if (signo == SIGUSR1) {
82 fprintf(stderr, "[%s] > Notified!\n", "process3");
83 struct queue_message msg;
84 /* Check queues from both other processes */
85 if (msgrcv(qid, &msg, sizeof(int), 3, 0) > 0) {
86 fprintf(stderr, "[%s] > Notified with value: %s!\n", "process3", strsignal(msg.signo[0]));
89 else if (msgrcv(qid, &msg, sizeof(int), 3, 0) > 0) {
90 fprintf(stderr, "[%s] > Notified with value: %s!\n", "process3", strsignal(msg.signo[0]));
94 else if (signo == SIGTERM) {
95 fprintf(stderr, "[%s] > Signalling other processes..\n", "process3");
96 processes->pids[2] = 0;
97 notify_other_processes(signo);
99 fprintf(stderr, "[%s] > Releasing resources\n", "process3");
100 close(read_descriptor);
103 else if (signo == SIGTSTP) {
104 fprintf(stderr, "[%s] > Signalling other processes..\n", "process3");
105 notify_other_processes(signo);
107 fprintf(stderr, "[%s] > Closing pipe\n", "process3");
108 close(read_descriptor);
111 else if (signo == SIGCONT) {
112 fprintf(stderr, "[%s] > Signalling other processes..\n", "process3");
113 notify_other_processes(signo);
115 fprintf(stderr, "[%s] > Opening pipe\n", "process3");
116 read_descriptor = open(read_pipe, O_RDONLY);
121 * Program grabs data (calculated number of characters) from process2 and prints
122 * grabbed data to the standard output.
125 /** Buffer used for storing data from input pipe */
128 /** Stores number of bytes read from input pipe in current iteration */
131 fprintf(stderr, "[%s] Init!\n", "process3");
134 * Register signals handled by process
136 if (signal(SIGUSR1, sig_handler) == SIG_ERR) {
137 fprintf(stderr, "can't catch SIGUSR1\n");
139 if (signal(SIGTERM, sig_handler) == SIG_ERR) {
140 fprintf(stderr, "can't catch SIGTERM\n");
142 if (signal(SIGTSTP, sig_handler) == SIG_ERR) {
143 fprintf(stderr, "can't catch SIGTSTP\n");
145 if (signal(SIGCONT, sig_handler) == SIG_ERR) {
146 fprintf(stderr, "can't catch SIGCONT\n");
150 * Register memory to share with other processes, and pass current
151 * process id to the array.
153 shmid = shmget(shmkey, sizeof(struct message), 0666);
155 processes = (struct message *)shmat(shmid, NULL, 0);
156 processes->pids[2] = getpid();
158 fprintf(stderr, "[%s] Shared pid: %d\n", "process3", getpid());
161 * Register message queue to communicate with other processes
163 qid = msgget(qkey, 0666);
165 /* Reading from process2 */
166 read_descriptor = open(read_pipe, O_RDONLY);
169 /* Read data from input pipe */
170 count = read(read_descriptor, &buffer, sizeof(int));
172 fprintf(stderr, "[%s] Fetched: %d bytes\n", "process3", count);
175 fprintf(stderr, "[%s] Process2 send: %d\n", "process3", buffer);
182 /* Release resources in normal program flow exit. */
183 close(read_descriptor);