header for public argument：shmdata.h
#define TEXT_SZ 2048
struct shared_use_st
{
int written;
char text[TEXT_SZ];
};
#endif
shmread.c
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/shm.h>
#include "shmdata.h"
int main()
{
int running = 1;
void *shm = NULL;
struct shared_use_st *shared;
int shmid;
shmid = shmget((key_t)1234, sizeof(struct shared_use_st), 0666|IPC_CREAT);
if(shmid == -1)
{
fprintf(stderr, "shmget failed\n");
exit(EXIT_FAILURE);
}
shm = shmat(shmid, 0, 0);
if(shm == (void*)-1)
{
fprintf(stderr, "shmat failed\n");
exit(EXIT_FAILURE);
}
shared = (struct shared_use_st*)shm;
shared->written = 0;
while(running)
{
if(shared->written != 0)
{
printf("You wrote: %s", shared->text);
sleep(rand() % 3);
shared->written = 0;
if(strncmp(shared->text, "end", 3) == 0)
running = 0;
}
else
sleep(1);
}
if(shmdt(shm) == -1)
{
fprintf(stderr, "shmdt failed\n");
exit(EXIT_FAILURE);
}
if(shmctl(shmid, IPC_RMID, 0) == -1)
{
fprintf(stderr, "shmctl(IPC_RMID) failed\n");
exit(EXIT_FAILURE);
}
exit(EXIT_SUCCESS);
}
shmwrite.c
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/shm.h>
#include "shmdata.h"
int main()
{
int running = 1;
void *shm = NULL;
struct shared_use_st *shared = NULL;
char buffer[BUFSIZ + 1];
int shmid;
shmid = shmget((key_t)1234, sizeof(struct shared_use_st), 0666|IPC_CREAT);
if(shmid == -1)
{
fprintf(stderr, "shmget failed\n");
exit(EXIT_FAILURE);
}
shm = shmat(shmid, (void*)0, 0);
if(shm == (void*)-1)
{
fprintf(stderr, "shmat failed\n");
exit(EXIT_FAILURE);
}
shared = (struct shared_use_st*)shm;
while(running)
{
while(shared->written == 1)
{
sleep(1);
printf("Waiting...\n");
}
printf("Enter some text: ");
fgets(buffer, BUFSIZ, stdin);
strncpy(shared->text, buffer, TEXT_SZ);
shared->written = 1;
if(strncmp(buffer, "end", 3) == 0)
running = 0;
}
if(shmdt(shm) == -1)
{
fprintf(stderr, "shmdt failed\n");
exit(EXIT_FAILURE);
}
sleep(2);
exit(EXIT_SUCCESS);
}