forked

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#define MSG_SZ_MAX 255

struct message{
    long mtype;
    pid_t pid;
    char mtext[MSG_SZ_MAX];
};

int descr;
struct message sendMsg, recieveMsg;

static void sigHandle(int signum);


void main(){
    descr = msgget(10, IPC_CREAT|0666);
    if(descr==-1){
        perror("msgget");
    }

    printf("descriptor : %d\n", descr);
    pid_t myPID = getpid();
    printf("PID : %d\n", myPID);

    if(signal(SIGINT, sigHandle) == SIG_ERR){
        perror("Can't handle a signal SIGINT.");
        exit(1);
    }
    if(signal(SIGUSR1, sigHandle) == SIG_ERR){
        perror("Can't handle a signal SIGUSR1.");
        exit(1);
    }
    if(signal(SIGTERM, sigHandle) == SIG_ERR){
        perror("Can't handle a signal SIGTERM.");
        exit(1);
    }

    //WHERE TO SEND
    printf("Receiver's PID : ");
    pid_t receiverPID;
    scanf("%d", &receiverPID);

    //setting sending msg metainfo
    sendMsg.mtype = receiverPID;
    sendMsg.pid = myPID;

    //setting recieve msg metainfo
    recieveMsg.mtype = myPID;


    fflush(stdout);
    if(fork() == 0){
        //printf("child's pid = %d\n", getpid());
        while(1){
            //printf("pid=%d,sending...\n", getpid());

            char buf[MSG_SZ_MAX];
            scanf("%s", buf);
            sprintf(sendMsg.mtext, "[%d] : %s", myPID, buf);

            if(msgsnd(descr, &sendMsg, sizeof(struct message), 0) == -1){
                perror("msgsnd");
                exit(2);
            }
        }
    } else {
        //printf("parent's pid = %d\n", getpid());
        while(1){
            //printf("pid=%d,receiving...\n", getpid());

            if(msgrcv(descr, &recieveMsg, sizeof(struct message), myPID, IPC_NOWAIT) != -1){
                printf("%s\n", recieveMsg.mtext);
            }
        }
    }
}

static void sigHandle(int signum){
    if(signum == SIGUSR1){
        printf("\nOther process has been terminated.\n");
        msgctl(descr, IPC_RMID, 0);
        exit(0);
    }
    if(signum == SIGINT){
        kill(recieveMsg.pid, SIGUSR1);
        msgctl(descr, IPC_RMID, 0);
        exit(0);
    }
    if(signum == SIGTERM){
        printf("\nSIGTERM has been received, terminated.\n");
        kill(recieveMsg.pid, SIGUSR1);
        msgctl(descr, IPC_RMID, 0);
        exit(0);
    }
}