#include <unistd.h>
int pipe(int filedes[2]);
int main(void)
{
int n;
int fd[2];
pid_t pid;
char line[MAXLINE];
if(pipe(fd) 0){ /* 先建立管道得到一对文件描述符 */
exit(0);
}
if((pid = fork()) 0) /* 父进程把文件描述符复制给子进程 */
exit(1);
else if(pid > 0){ /* 父进程写 */
close(fd[0]); /* 关闭读描述符 */
write(fd[1], "\nhello world\n", 14);
}
else{ /* 子进程读 */
close(fd[1]); /* 关闭写端 */
n = read(fd[0], line, MAXLINE);
write(STDOUT_FILENO, line, n);
}
exit(0);
}
#include <sys/types.h>#include <sys/stat.h>
int mkfifo(const char *filename, mode_t mode);
int mknode(const char *filename, mode_t mode | S_IFIFO, (dev_t) 0 );
#include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <sys/stat.h>
int main()
{
int res = mkfifo("/tmp/my_fifo", 0777);
if (res == 0)
{
printf("FIFO created/n");
}
exit(EXIT_SUCCESS);
}
int semget(key_t key, int num_sems, int sem_flags);
int semop(int sem_id, struct sembuf *sem_opa, size_t num_sem_ops);
· 1
struct sembuf{
short sem_num;//除非使用一组信号量，否则它为0
short sem_op;//信号量在一次操作中需要改变的数据，通常是两个数，一个是-1，即P（等待）操作，
//一个是+1，即V（发送信号）操作。
short sem_flg;//通常为SEM_UNDO,使操作系统跟踪信号，
//并在进程没有释放该信号量而终止时，操作系统释放信号量
};
int semctl(int sem_id, int sem_num, int command, ...);
· 1
union semun{
int val;
struct semid_ds *buf;
unsigned short *arry;
};
struct msg_queue {
struct kern_ipc_perm q_perm;
time_t q_stime; /* last msgsnd time */
time_t q_rtime; /* last msgrcv time */
time_t q_ctime; /* last change time */
unsigned long q_cbytes; /* current number of bytes on queue */
unsigned long q_qnum; /* number of messages in queue */
unsigned long q_qbytes; /* max number of bytes on queue */
pid_t q_lspid; /* pid of last msgsnd */
pid_t q_lrpid; /* last receive pid */
struct list_head q_messages;
struct list_head q_receivers;
struct list_head q_senders;
};
struct msqid_ds {
struct ipc_perm msg_perm;
struct msg *msg_first; /* first message on queue,unused */
struct msg *msg_last; /* last message in queue,unused */
__kernel_time_t msg_stime; /* last msgsnd time */
__kernel_time_t msg_rtime; /* last msgrcv time */
__kernel_time_t msg_ctime; /* last change time */
unsigned long msg_lcbytes; /* Reuse junk fields for 32 bit */
unsigned long msg_lqbytes; /* ditto */
unsigned short msg_cbytes; /* current number of bytes on queue */
unsigned short msg_qnum; /* number of messages in queue */
unsigned short msg_qbytes; /* max number of bytes on queue */
__kernel_ipc_pid_t msg_lspid; /* pid of last msgsnd */
__kernel_ipc_pid_t msg_lrpid; /* last receive pid */
};
struct kern_ipc_perm{ //内核中记录消息队列的全局数据结构msg_ids能够访问到该结构；
key_t key; //该键值则唯一对应一个消息队列
uid_t uid;
gid_t gid;
uid_t cuid;
gid_t cgid;
mode_t mode;unsigned long seq;
}
struct msgbuf{long mtype;char mtext[1];
};
