mmm.c

#include <stdio.h>
#include <string.h>
#include <mpi.h>

const int MAX_STRING = 100;

int main(void) {
    char  greeting[MAX_STRING];
    int   comm_sz;
    int   my_rank;

    MPI_Init(NULL, NULL);
    MPI_Comm_size(MPI_COMM_WORLD, &comm_sz);
    MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);

    if (my_rank != 0) {
        sprintf(greeting, "Greetings from process %d of %d",
                my_rank, comm_sz);
        MPI_Send(greeting, strlen(greeting)+1, MPI_CHAR, 0, 0,
                 MPI_COMM_WORLD);
    } else {
        printf("Greetings from process %d of %d\n", my_rank, comm_sz);
        for (int q = 0; q < comm_sz; q++) {
            MPI_Recv(greeting, MAX_STRING, MPI_CHAR, q,
                     0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
            printf("%s\n", greeting);
        }
    }

    MPI_Finalize();
    return 0;
}