兩個子進程間可以使用命名管道，非常簡單。管道如果文件一樣存在硬盤中，使用ls可以查看，管道文件0字節。使用fork函數分別創建兩個子進程。
一個負責讀數據，一個負責寫數據。

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/wait.h>#define FIFO_PATH "./fifo_fork_demo"
#define MSG       "Hello from child writer!\n"int main(void)
{/* 1. 創建有名管道 ----------------------------------------------------- */if (mkfifo(FIFO_PATH, 0666) == -1) {perror("mkfifo");return 1;}/* 2. fork 兩個子進程 --------------------------------------------------- */pid_t writer_pid = fork();if (writer_pid == 0) {                        /* 子進程 A：寫 */int fd = open(FIFO_PATH, O_WRONLY);       /* 阻塞到有讀端 */if (fd == -1) { perror("open writer"); _exit(1); }write(fd, MSG, sizeof(MSG));close(fd);_exit(0);}pid_t reader_pid = fork();if (reader_pid == 0) {                        /* 子進程 B：讀 */int fd = open(FIFO_PATH, O_RDONLY);       /* 阻塞到有寫端 */if (fd == -1) { perror("open reader"); _exit(1); }char buf[64];ssize_t n = read(fd, buf, sizeof(buf) - 1);if (n > 0) {buf[n] = '\0';printf("reader child got: %s", buf);}close(fd);_exit(0);}/* 3. 父進程等待兩個子進程結束 ----------------------------------------- */int st;waitpid(writer_pid, &st, 0);waitpid(reader_pid, &st, 0);/* 4. 清理 FIFO --------------------------------------------------------- */unlink(FIFO_PATH);puts("parent: all children finished, fifo removed.");return 0;
}