c - 如何从标准输入读取数字直到结束

Question

在有 for(;;) 的地方，我需要从 stdin 读取一些内容并保存到 N。可能有 read(stdin,N,sizeof(float)) 和 while(s!=EOF) s=getc(stdin) 吗？ 我假设数字列表保存在标准输入分隔的行尾

问题是这样的:

Your program must print its pid to standard output. Then it should start to read values of N from standard input until the end of the file. After receiving a signal (SIGUSR1) your program should subtract (then multiply, then divide, then subtract) the value of N from sum (first value of sum=0) as a cycle. After receiving SIGUSR2 your program should print the current sum.

我如何解释问题和尝试:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>

float N,sum=0;
int count=0;

void handler(int s){
    count++;
    if (s==SIGUSR1){
        if (count==1){
            sum-=N;
        }   
        if (count==2){
            sum*=N;
        }
        if (count==3){
            sum/=N;
        }
        if (count==4){
            sum+=N;
            count==0;
        }

    }

    else if (s==SIGUSR2){
        printf("sum=%d",sum);
    }
}


int main(){
    pid_t pid=getpid();
    signal(SIGUSR1,handler);
    signal(SIGUSR2,handler);
    printf("%d",pid);
    fflush(stdout); 

    for(;;)
    scanf("%d",&N);


    return(0);
}

Answer 1

检查scanf的返回值。它返回成功匹配的项目数，因此如果它不返回 1，那么就完成了。

while (scanf("%d", &N) == 1)
    ;