Added initial inter-process communication: Sharing pids between processes.

[wsti_so.git] / src / process1.c

diff --git a/src/process1.c b/src/process1.c
index ad4b9111984c64b4079a78e32a41f912fcf965de..b28563f4102faf831cf12deecd2ff440eb3b0216 100644 (file)
--- a/src/process1.c
+++ b/src/process1.c
@@ -8,6 +8,9 @@
 /* Signals handling.. */
 #include <signal.h>
 
+#include <sys/shm.h>
+
+
 /** If buffer is too small to hold entire string, it is incremented by this value */
 #define BUFFER_STEP 16
 
@@ -20,16 +23,39 @@ char * write_pipe = "/tmp/process1pipe";
 /** File descriptor of pipe */
 int file_descriptor;
 
+
+/**
+ * Shared memory variables
+ */
+/**
+ * Memory key for processes. Must be same between all processes to properly
+ * communicate.
+ */
+key_t shmkey = 18912;
+/**
+ * Id of the shared memory
+ */
+int shmid;
+
+/**
+ * Message shared by processes. Contains array of process IDs
+ */
+struct message {
+       pid_t pids[3];
+};
+
+struct message * processes = NULL;
+
 /**
  * Handler for signals.
  */
 void sig_handler(int signo)
 {
+       fprintf(stderr, "[%s] Received %s!\n", "process1", strsignal(signo));
        if (signo == SIGUSR1) {
-               fprintf(stderr, "[%s] Received SIGUSR1!\n", "process1");
        }
-       else if (signo == SIGQUIT) {
-               fprintf(stderr, "[%s] Received SIGQUIT!\n", "process1");
+       else if (signo == SIGTERM) {
+               int i = 0;
                fprintf(stderr, "[%s] > Releasing resources\n", "process1");
                close(write_pipe);
                unlink(write_pipe);
@@ -38,15 +64,17 @@ void sig_handler(int signo)
                        free(buffer);
                        buffer = NULL;
                }
+               for (; i < 3; i++) {
+                       fprintf(stderr, "[%s] Process %d, PID: %d\n", "process3", i, processes->pids[i]);
+               }
                exit(0);
        }
-       else if (signo == SIGINT) {
-               fprintf(stderr, "[%s] Received SIGINT!\n", "process1");
+       else if (signo == SIGTSTP) {
                fprintf(stderr, "[%s] > Closing pipe\n", "process1");
                close(write_pipe);
+               raise (SIGSTOP);
        }
        else if (signo == SIGCONT) {
-               fprintf(stderr, "[%s] Received SIGCONT!\n", "process1");
                fprintf(stderr, "[%s] > Opening pipe\n", "process1");
                file_descriptor = open(write_pipe, O_WRONLY);
        }
@@ -80,16 +108,25 @@ int main(void) {
        if (signal(SIGUSR1, sig_handler) == SIG_ERR) {
                fprintf(stderr, "can't catch SIGUSR1\n");
        }
-       if (signal(SIGQUIT, sig_handler) == SIG_ERR) {
-               fprintf(stderr, "can't catch SIGQUIT\n");
+       if (signal(SIGTERM, sig_handler) == SIG_ERR) {
+               fprintf(stderr, "can't catch SIGTERM\n");
        }
-       if (signal(SIGINT, sig_handler) == SIG_ERR) {
-               fprintf(stderr, "can't catch SIGINT\n");
+       if (signal(SIGTSTP, sig_handler) == SIG_ERR) {
+               fprintf(stderr, "can't catch SIGTSTP\n");
        }
        if (signal(SIGCONT, sig_handler) == SIG_ERR) {
                fprintf(stderr, "can't catch SIGCONT\n");
        }
 
+       /*
+        * Register memory to share with other processes, and pass current
+        * process id to the array.
+        */
+       shmid = shmget(shmkey, sizeof(struct message), IPC_CREAT | 0666);
+
+       processes = (struct message *)shmat(shmid, NULL, 0);
+       processes->pids[0] = getpid();
+
        mkfifo(write_pipe, 0666);
 
        file_descriptor = open(write_pipe, O_WRONLY);