[英]Creating PIPE blocks
I created a PIPE using the below code. 我使用以下代码创建了PIPE。 But there is something wrong when the program runs fd = open(FIFO, O_RDONLY);
但是当程序运行fd = open(FIFO, O_RDONLY);
. 。 The phenomenon is blocking. 该现象正在阻止。 Could someone give me some advice? 有人可以给我一些建议吗? Thanks a lot . 非常感谢 。
#include<errno.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<stdio.h>
#define FIFO "/tmp/test"
int main(int argc, char** argv)
{
char buf_r[100];
int fd;
int nread;
if((mkfifo(FIFO, O_CREAT) < 0) && (errno != EEXIST))
{
printf("can not create FIFO\n");
exit(1);
}
printf("Prepare read data\n");
fd = open(FIFO, O_RDONLY);
if(fd == -1)
{
exit(1);
}
while(1)
{
if((nread = read(fd, buf_r, 100)) == -1)
{
if(errno == EAGAIN) printf("No data\n");
}
if(buf_r[0]=='Q') break;
buf_r[nread]=0;
printf("data is:%s\n", buf_r);
sleep(1);
}
}
Opening a FIFO blocks until a "communication peer" is connected to the FIFO as well so that the pipe is successfully established. 打开FIFO块,直到“通信对等体”也连接到FIFO,以便成功建立管道为止。
BTW, when creating the FIFO fails, you should output (at most) a warning and continue - there are chances that the FIFO already exists and can be reused. 顺便说一句,当创建FIFO失败时,您应该最多输出警告并继续-FIFO已经存在并且可以重复使用的机会。 And maybe /root/test/test
is not the best place for this FIFO... 也许/root/test/test
不是此FIFO的最佳位置...
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