c - 伪终端不打印输出

Question

下面是我的代码，旨在打开一个额外的 gnome 终端并在新打开的终端控制台中打印前 20 个斐波那契数:

#include <stdio.h>
#include "apue.h"

int Fibonacci(unsigned int n);

int main() {
    char cmd[256];
    char str[40][256];
    char *name = tempnam(NULL, NULL);
    char *line = "\n";
    FILE *log;

    mkfifo(name, 0777);
    log = fopen(name, "w+");

    for (unsigned int i = 0; i < 20; i++) {
         sprintf(str[(2 * i)], "%s",line);
         fputs(str[(2 * i)], log);
         sprintf(str[(2 * i) + 1], "%u\n", Fibonacci(i));
         fputs(str[(2 * i) + 1], log);
         fflush(NULL);
    }
    if (fork() == 0) {
        sprintf(cmd, "gnome-terminal -e cat %s", name);
        system(cmd);       
        for (unsigned int j = 0; j < 40 ; j++) {    
            fgets(str[j], sizeof(cmd), log);            
        }
        exit(0);
    } else
    if (fork() < 0) {
        perror("fork () error");    
    }
}

int Fibonacci(unsigned int n) {
    if (n == 0) {
        return 0;
    } else
    if (n == 1) {
        return 1;
    } else
    if (n > 1) {
        return Fibonacci(n - 2) + Fibonacci(n - 1);
    }
}

当我编译它时，我收到以下警告消息:

-*- mode: compilation; default-directory: "/usr/lib/gcc/x86_64-linux-gnu/4.8.4/include/" -*-
Compilation started at Sun Sep  3 15:46:28

gcc  -o FIB0   Fibonacci.c
/tmp/ccobnJV9.o: In function `main':
Fibonacci.c:(.text+0x231f): warning: the use of `tempnam' is dangerous, better use `mkstemp'

Compilation finished at Sun Sep  3 15:46:28

当我从 gnome 终端命令行执行它时，新终端弹出，但没有输出!我如何修复这段代码以使其工作？

当我使用

 sprintf(cmd, "xterm -e cat %s", name);

而不是“gnome-terminal”，它工作正常。那么如何使用 GCC 在 gnome 终端之间进行通信呢？

Answer 1

你的 fork 机制有一个额外的问题:

if (fork() == 0) {
    /* do something in the child */
} else
if (fork() < 0) {   //<--- fork AGAIN!
    perror("fork () error");    
}

父进程 fork 了两次!

您应该改为存储 pid:

int pid = fork();
if (pid == 0) {
    /* do something in the child */
} else
if (pid < 0) {
    perror("fork () error");    
}