使用命令行参数中的getchar和putchar编码程序以发送以进行解码 [英] encode program using getchar from command line argument and putchar to send to decode

问题描述

所以我正在尝试制作一个编码/解码程序。到目前为止，我还停留在编码部分。我必须能够从命令行参数中获取一条消息，并使用种子随机数对其进行编码。该数字将由用户作为第一个参数给出。

So I'm trying to make a encode/decode program. So far I'm stuck in the encode part. I have to be able to get a message from the command line arguments, and encode it using a seeded random number. This number will be given by the user as the first argument.

我的想法是从getchar中获取整数，然后向其中添加随机数结果。然后，我想将其返回到std，以便另一个程序可以将其读取为参数，以使用相同的种子对其进行解码。到目前为止，我无法正常使用Putchar。对我应该解决或关注的问题有任何想法吗？提前致谢！

My idea is to get the int from getchar and just add random number result to it. I then want to get it back to the std out so that another program can read it as an argument to decode it using the same seed. So far, I can't get the putchar to work properly. Any ideas on what I should fix or focus in? Thanks in advance!

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

int main(int argc, char *argv[]) { 
    int pin, charin, charout;
    // this verifies that a key was given at for the first argument
    if (atoi(argv[1]) == 0) {
        printf("ERROR, no key was found..");
        return 0;
    } else {
        pin = atoi(argv[1]) % 27; // atoi(argv[1])-> this part should seed the srand
    }    

    while ((getchar()) != EOF) {        
        charin = getchar();        
        charout = charin + pin;        
        putchar(charout);        
    }    
}

推荐答案

您不应两次调用 getchar（），它会消耗流中的字符，而您会丢失它们，请尝试这样

You should not call getchar() twice, it consumes the characters in the stream and you lose them, try like this

while ((charin = getchar()) != EOF) {
    charout = charin + pin;
    putchar(charout);
}

此外，也不要检查 atoi（）返回 0 这是一个数字和有效的种子，执行此操作

Also, instead of checking if atoi() returns 0 which is a number and a valid seed, do this

char *endptr;
int pin;
if (argc < 2) {
    fprintf(stderr, "Wrong number of parameters passed\n");
    return -1;
}
/* strtol() is declared in stdlib.h, and you already need to include it */
pin = strtol(argv[1], &endptr, 10);
if (*endptr != '\0') {
    fprintf(stderr, "You must pass an integral value\n");
    return -1;
}

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