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如何从命令行读取参数到双精度?

[英]How to read an argument in from command line into a double?

这个程序首先分叉然后由execlp运行,它的调用程序传递两个数字,一个幂和一个基数。

int main(int argc, char *argv[])
{
    int pid = getpid();
    printf("Calculator Process[%d]: started\n",pid);
    double base, power;
    sscanf(argv[1],"%d",&base);
    sscanf(argv[2],"%d",&power);
    double number = pow(base,power);
    printf("Calculator Process[%d]: %d ^^ %d == %d\n",pid,base,power,number);
    printf("Calculator Process[%d]: exiting\n",pid);
    return 1;
}

让我们说我进入它的基础3,力量5.这就是我得到的:

base = 4263 -- this also happens to be the PID. 
power = -1 
raised to power: 714477568

通话线路:

execlp("./calculator","./calculator",argv[1],argv[2],(char*)0);

当我打印argvs时,我得到它们的值(作为char *,但是转换失败)。

任何想法为什么我不能正确读入值?

阅读双倍:

double base, power;
sscanf(argv[1],"%lf",&base);
sscanf(argv[2],"%lf",&power);

或者扫描成整数:

int base, power;
sscanf(argv[1],"%d",&base);
sscanf(argv[2],"%d",&power);

快速调整代码应该这样做:

int main(int argc, char *argv[]) 
{
    int pid = getpid();
    printf("Calculator Process[%d]: started\n",pid);
    double base, power;
    base = atof(argv[1]);
    power = atof(argv[2]);
    double number = pow(base,power);
    printf("Calculator Process[%d]: %f ^^ %f == %f\n",pid,base,power,number);
    printf("Calculator Process[%d]: exiting\n",pid);
    return 1; 

}

  1. 要将char数组转换为数字,可以使用atof()
  2. 不要忘记将printf更新为double %f否则它们将无法在输出中显示!

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