我爲FIFO寫測試。服務器通過FIFO向客戶端寫入字符串「hello」。但似乎這兩個進程都被阻塞了。我認爲先進先出是爲服務器和客戶端的寫入和讀取而打開的。但是這兩個進程什麼都不輸出。當打開FIFO時,爲什麼進程被阻塞
/* FIFO test */
#include <stdio.h>
#include <sys/types.h>
#include <sys.stat.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#define FIFOPATH "/home/hel/fifo" // define file path
int client(void);
int server(void);
int main(void)
{
pid_t pid;
/* create FIFO */
if (mkfifo(FIFOPATH, S_IRUSR | S_IWUSR) < 0) {
if (errno == EEXIST) { // already exists, ok
}
/* error */
else {
exit(-1);
}
}
/* create process */
pid = fork();
if (pid < 0) { // error, process exits.
exit(-1);
} else if (pid == 0) { // child, server
server();
return 0; // exit
}
/* parent, client */
client();
return 0;
}
/* server */
int server(void)
{
int ret;
int fd;
/* open fifo for writing */
if ((fd = open(FIFOPATH, 0200)) < 0) {
printf("%s\n", strerror(errno));
return -1; // error
}
ret = write(fd, "hello", 5);
close(fd);
return 0;
}
/* client */
int client(void)
{
char recvBuf[100];
int fd;
int ret;
/* open fifo for reading */
if ((fd = open(FIFOPATH, 0400)) < 0) {
printf("%s\n", strerror(errno));
return -1; // error
}
ret = read(fd, recvBuf, 5);
printf("ret: %d %d\n", ret, fd);
printf("client receive %s\n", recvBuf);
close(fd);
return 0;
}