shared_s.c

#include <sys/types.h> 
#include <sys/ipc.h> 
#include <sys/shm.h> 
#include <stdio.h> 
#include<stdlib.h> 
#define SHMSZ 27 
 
void main() 
{ 
    char c; 
    int shmid; 
    key_t key; 
    char *shm, *s; 
 
    /* 
     * We'll name our shared memory segment 
     * "5678". 
     */ 
    key = 5678; 

 
    /* 
     * Create the segment. 
     */ 
    if ((shmid = shmget(key, SHMSZ, IPC_CREAT | 0666)) < 0) { 
        perror("shmget"); 
        exit(1); 
    } 
 
    /* 
     * Now we attach the segment to our data space. 
     */ 
    if ((shm = shmat(shmid, NULL, 0)) == (char *) -1) { 
        perror("shmat"); 
        exit(1); 
    } 
 
    /* 
     * Now put some things into the memory for the 
     * other process to read. 
     */ 
    s = shm; 
 
    for (c = 'a'; c <= 'z'; c++) 
        *s++ = c; 
    *s = '\0'; 

 
    /* 
     * Finally, we wait until the other process  
     * changes the first character of our memory 
     * to '*', indicating that it has read what  
     * we put there. 
     */ 
    while (*shm != '*') 
        sleep(1); 
 
    exit(0); 
}