c - 带管道的非终止 C 程序

Question

我正在尝试编写一个C程序，使用管道在两个 child 之间玩“石头、剪刀、布”的游戏。我已经编写并运行了大部分代码。当我运行代码时，它会玩游戏，但拒绝终止。它锁定了终端，并迫使我关闭它并重试。我不确定这是为什么。

    #include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>
    #include <string.h>
    #include <errno.h>
    #include <time.h>

    static char* const ARGV[] = {
          "prog","4",NULL
    };

   int main(int argc, char *argv[]) {
   int pipe1[2], pipe2[2], pipe3[2], pipe4[2];
   int pid, pid2, cpid;
   int turns, readbyte;
   char message[100];
   int object, i, status;
   char p1[5], p2[5], choice[5];
   srand(time(NULL));


if((argc != 2) || ((turns = atoi(argv[1])) <= 0)) {
    fprintf(stderr, "Usage: %s turns\n",argv[0]);
    exit(1);
}

if(pipe(pipe1) == -1) {
    perror("Could not create pipe");
    exit(1);
}

if(pipe(pipe2) == -1) {
    perror("Could not create pipe");
    exit(1);
}

if(pipe(pipe3) == -1) {
    perror("Could not reach pipe");
    exit(1);
}

if(pipe(pipe4) == -1) {
    perror("Could not reach pipe");
    exit(1);
}


if(pid = fork()) {
    write(pipe1[1], "Ready", strlen("Ready")+1);
    for(i=1; i <= turns; i++) {
        readbyte = read(pipe2[0],message,100);
        srand(time(NULL));
        object = rand() % 3;
        sprintf(choice,"%d",object);
        write(pipe1[1],choice,strlen(choice)+1);
    }
}

if(pid = fork()) {
    write(pipe3[1], "Ready", strlen("Ready")+1);
    for(i=1; i<=turns; i++){
        readbyte = read(pipe4[0],message,100);
        sleep(1);
        srand(time(NULL));
        object = rand()%3;
        sprintf(choice,"%d",object);
        write(pipe3[1],choice,strlen(choice)+1);
    }
}

cpid = wait(&status);
readbyte = read(pipe3[0],message,100);
readbyte = read(pipe1[0],message,100);
printf("Child 1 PID: %d\n", getpid());
printf("Child 2 PID: %d\n", getpid()-1);

printf("A brawl is surely brewing\n%d Rounds\nFight! \n",turns);
for(i=1; i<=turns; i++){
    write(pipe2[1],"Go",strlen("Go")+1);
    write(pipe4[1],"Go",strlen("Go")+1);
    readbyte = read(pipe1[0],p1,5);
    readbyte = read(pipe3[0],p2,5);

    printf("Round %d:\n",i);

    if((atoi(p1)) == 0){
        printf("Child 1 throws Rock\n");
    }
    else if((atoi(p1)) == 1){
        printf("Child 1 throws Paper\n");
    }
    else{
        printf("Child 1 throws Scissors\n");
    }
    if((atoi(p2)) == 0){
        printf("Child 2 throws Rock\n");
    }
    else if((atoi(p2)) == 1){
        printf("Child 2 throws Paper\n");
    }
    else{
        printf("Child 2 throws Scissors\n");
    }
    if(atoi(p1) == atoi(p2)){
        printf("This round is a tie\n");
    }
    else if((atoi(p1) == 0) && (atoi(p2) == 2)){
        printf("Rock beats Scissors: Child 1 wins!\n");
    }
    else if((atoi(p1) == 0) && (atoi(p2) == 1)){
        printf("Paper beats Rock: Child 2 wins!\n");
    }
    else if((atoi(p1) == 1) && (atoi(p2) == 0)){
        printf("Paper beats Rock: Child 1 wins!\n");
    }
    else if((atoi(p1) == 1) && (atoi(p2) == 2)){
        printf("Scissors beats Paper: Child 2 wins!\n");
    }
    else if((atoi(p1) == 2) && (atoi(p2) == 1)){
        printf("scissors beats Paper: Child 1 wins!\n");
    }
    else if(((atoi(p1)) == 2) && (atoi(p2) == 0)){
        printf("Rock beats Scissors: Child 2 wins!\n");
    }
}
}

Answer 1

Fork() 使子进程继承父进程的打开文件描述符，包括 pipeline()。当所有“编写者”都关闭其管道时，管道将变得不可读(EOF)。您打开了管道的无关“写入”端，因此它将无法正确关闭。

至少，您需要父级关闭 pipeline1[1]、pipe3[1]。稍微检查一下返回值可能也不会损害您的努力。