From: Rafał Długołęcki <rafal@dlugolecki.net.pl>
Date: Sat, 21 Jun 2014 09:43:53 +0000 (+0200)
Subject: Added initial inter-process communication: Sharing pids between processes.
X-Git-Url: https://git.dlugolecki.net.pl/?a=commitdiff_plain;h=f0a7f7a71896b25cc524598e5472c821f987a71c;p=wsti_so.git

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

diff --git a/src/process1.c b/src/process1.c
index 9fdee30..b28563f 100644
--- 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
 
@@ -20,6 +23,29 @@ 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.
  */
@@ -29,6 +55,7 @@ void sig_handler(int signo)
 	if (signo == SIGUSR1) {
 	}
 	else if (signo == SIGTERM) {
+		int i = 0;
 		fprintf(stderr, "[%s] > Releasing resources\n", "process1");
 		close(write_pipe);
 		unlink(write_pipe);
@@ -37,6 +64,9 @@ 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 == SIGTSTP) {
@@ -88,6 +118,15 @@ int main(void) {
 		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);
diff --git a/src/process2.c b/src/process2.c
index 4908173..2417fe8 100644
--- a/src/process2.c
+++ b/src/process2.c
@@ -8,6 +8,8 @@
 /* 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
 
@@ -23,6 +25,31 @@ int read_descriptor;
 /** Descriptor of output pipe */
 int write_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.
  */
@@ -32,10 +59,14 @@ void sig_handler(int signo)
 	if (signo == SIGUSR1) {
 	}
 	else if (signo == SIGTERM) {
+		int i = 0;
 		fprintf(stderr, "[%s] > Releasing resources\n", "process2");
 		close(read_descriptor);
 		close(write_descriptor);
 		unlink(write_descriptor);
+		for (; i < 3; i++) {
+			fprintf(stderr, "[%s] Process %d, PID: %d\n", "process3", i, processes->pids[i]);
+		}
 		exit(0);
 	}
 	else if (signo == SIGTSTP) {
@@ -90,6 +121,15 @@ int main(void) {
 		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[1] = getpid();
+
 	/* Reading from process1 */
 	read_descriptor = open(read_pipe, O_RDONLY);
 
diff --git a/src/process3.c b/src/process3.c
index 12efd40..b1b9972 100644
--- a/src/process3.c
+++ b/src/process3.c
@@ -9,12 +9,38 @@
 /* Signals handling.. */
 #include <signal.h>
 
+#include <sys/shm.h>
+
 /** Named pipe used to communicate with process2 */
 char * read_pipe = "/tmp/process2pipe";
 
 /** Descriptor of input pipe */
 int read_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.
  */
@@ -24,8 +50,12 @@ void sig_handler(int signo)
 	if (signo == SIGUSR1) {
 	}
 	else if (signo == SIGTERM) {
+		int i = 0;
 		fprintf(stderr, "[%s] > Releasing resources\n", "process3");
 		close(read_descriptor);
+		for (; i < 3; i++) {
+			fprintf(stderr, "[%s] Process %d, PID: %d\n", "process3", i, processes->pids[i]);
+		}
 		exit(0);
 	}
 	else if (signo == SIGTSTP) {
@@ -68,6 +98,15 @@ int main(void) {
 		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[2] = getpid();
+
 	/* Reading from process2 */
 	read_descriptor = open(read_pipe, O_RDONLY);