shmread.c
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#define ERR_EXIT(m) \
do \
{ \
perror(m); \
exit(EXIT_FAILURE); \
} while(0)
typedef struct stu
{
int age;
char name[32];
} STU;
int main(int argc, char *argv[])
{
int shmid;
shmid = shmget(1234, 0, 0);
if (shmid == -1)
ERR_EXIT("shmget");
STU *p;
p = shmat(shmid, NULL, 0);
if (p == (void*)-1)
ERR_EXIT("shmat");
printf("name = %s age = %d\n", p->name, p->age);
memcpy(p, "quit", 4);
shmdt(p);
return 0;
}
shmwrite.c
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#define ERR_EXIT(m) \
do \
{ \
perror(m); \
exit(EXIT_FAILURE); \
} while(0)
typedef struct stu
{
int age;
char name[32];
} STU;
int main(int argc, char *argv[])
{
int shmid;
shmid = shmget(1234, sizeof(STU), IPC_CREAT | 0666);
if (shmid == -1)
ERR_EXIT("shmget");
STU *p;
p = shmat(shmid, NULL, 0);
if (p == (void*)-1)
ERR_EXIT("shmat");
strcpy(p->name, "lisi");
p->age = 20;
while (1)
{
if (memcmp(p, "quit", 4) == 0)
break;
}
shmdt(p);
shmctl(shmid, IPC_RMID, NULL);
return 0;
}
makefile:
.PHONY:clean all
CC=gcc
CFLAGS=-Wall -g
BIN=shmwrite shmread
all:$(BIN)
%.o:%.c
$(CC) $(CFLAGS) -c $< -o [email protected]
clean:
rm -f *.o $(BIN)
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