#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <errno.h>


main()
{
	int uid, gid, mode, bytes;
	int rtrn, msqid, command, choice;
	struct msqid_ds msqid_ds, *buf;

	buf = &msqid_ds;

	printf("Enter the msqid: ");
	scanf("%i", &msqid);

	printf("\n1 = IPC_STAT\n2 = IPC_SET\n3 = IPC_RMID\n");
	printf("Enter command number: ");
	scanf("%i", &command);

	printf("\n\nmsqid = %d, command = %d\n", msqid, command);

	switch (command) {
		case 1:
			rtrn = msgctl(msqid, IPC_STAT, buf);
			if (rtrn != -1) {
				printf("User %d, group %d, perms 0%o\n",
					buf->msg_perm.uid, buf->msg_perm.gid,
					buf->msg_perm.mode);
				printf("cbytes: %d, qnum: %d, qbytes %d\n",
					buf->msg_cbytes, buf->msg_qnum, 
					buf->msg_qbytes);
			}
			break;

		case 2:
			rtrn = msgctl(msqid, IPC_STAT, buf);
			if (rtrn == -1)
				break;
			printf("\n1 = uid, 2 = gid, 3 = mode, 4 = qbytes\n");
			printf("Number of field to change: ");
			scanf("%i", &choice);
			switch (choice) {
				case 1:
					printf("\nUser id: ");
					scanf("%i", &uid);
					buf->msg_perm.uid = uid;
					printf("User = %d\n", buf->msg_perm.uid);
					break;
				case 2:
					printf("\nGroup id: ");
					scanf("%i", &gid);
					buf->msg_perm.gid = gid;
					printf("Group = %d\n", buf->msg_perm.gid);
					break;
				case 3:
					printf("\nMode: ");
					scanf("%i", &mode);
					buf->msg_perm.mode = mode;
					printf("Mode = 0%o\n", buf->msg_perm.mode);
					break;
				case 4:
					printf("\nQbytes: ");
					scanf("%i", &bytes);
					buf->msg_qbytes = bytes;
					printf("Qbytes = %d\n", buf->msg_qbytes);
					break;
			}
			rtrn = msgctl(msqid, IPC_SET, buf);
			break;

		case 3:
			rtrn = msgctl(msqid, IPC_RMID, NULL);
			break;
	}

	if (rtrn == -1)
		perror("msgctl");

	exit(0);
}