add share memory examples

related_info/lab7/ipc/shmem/shmem_client.c

@@ -0,0 +1,64 @@
+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/shm.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+
+#define SHMSZ     1024
+
+main()
+{
+	int shmid;
+	key_t key;
+	char *shm, *s;
+
+	/*
+	* We need to get the segment named
+	* "1234", created by the server.
+	*/
+	key = 1234;
+
+	/*
+	* Locate the segment.
+	*/
+	if ((shmid = shmget(key, SHMSZ, 0666)) < 0) {
+		perror("shmget");
+		return 1;
+	}
+
+	/*
+	* Now we attach the segment to our data space.
+	*/
+	if ((shm = shmat(shmid, NULL, 0)) == (char *) -1) {
+		perror("shmat");
+		return 1;
+	}
+
+	/*
+	* Zero out memory segment
+	*/
+	memset(shm,0,SHMSZ);
+	s = shm;
+
+	/*
+	* Client writes user input character to memory
+	* for server to read.
+	*/
+	for(;;){
+		char tmp = getchar();
+		// Eat the enter key
+		getchar();
+
+		if(tmp == 'q'){
+			*shm = 'q';
+			break;
+		}
+		*shm = tmp;
+	}
+
+	if(shmdt(shm) != 0)
+		fprintf(stderr, "Could not close memory segment.\n");
+
+	return 0;
+}

related_info/lab7/ipc/shmem/shmem_server.c

@@ -0,0 +1,62 @@
+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/shm.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+
+#define SHMSZ 1024
+
+main(int argc, char **argv)
+{
+	char c, tmp;
+	int shmid;
+	key_t key;
+	char *shm, *s;	
+
+    /*
+     * Shared memory segment at 1234
+     * "1234".
+     */
+	key = 1234;
+
+    /*
+     * Create the segment and set permissions.
+     */
+	if ((shmid = shmget(key, SHMSZ, IPC_CREAT | 0666)) < 0) {
+		perror("shmget");
+		return 1;
+	}
+
+    /*
+     * Now we attach the segment to our data space.
+     */
+	if ((shm = shmat(shmid, NULL, 0)) == (char *) -1) {
+		perror("shmat");
+		return 1;
+	}
+
+	/*
+	 * Zero out memory segment
+	 */
+	memset(shm,0,SHMSZ);
+	s = shm;
+
+	/*
+	* Read user input from client code and tell
+	* the user what was written.
+	*/
+	while (*shm != 'q'){
+		sleep(1);
+		if(tmp == *shm)
+			continue;
+
+		fprintf(stdout, "You pressed %c\n",*shm);
+		tmp = *shm;
+	}
+
+	if(shmdt(shm) != 0)
+		fprintf(stderr, "Could not close memory segment.\n");
+
+	return 0;
+}