Question

我正在尝试从K＆amp; R C 2.9获取getbits并传递包含ints的文本文件，检查以确保getbits（）可以处理它们，并将输出格式化为另一个txt文件。我很难过，我的导师告诉我不要使用fscanf，使用stdin和scanf。

这是我的代码

include <stdio.h>


unsigned int getbits(unsigned int x, int p, int n) 
{
  return (x >> (p + 1 - n)) &  ~(~0 << n);
}


int main()
{
  File * ipf = fopen("input.txt", "r");
  int x = 0 , p = 0, n = 0, b = 0;

  while(fscanf(ipf, "%d, %d, %u", &p, &n, &x) != EOF)
  {

    if(x < 4294967296 && p < 32 && n < p + 2)
    { 
      b = getbits(x,p,n);
      printf("gebits( x = %u, p = %d, n =  %d) = %u\n", x, p, n, b);
    } 
    else { printf("ERROR"); }
  }

  return 0;
}

input.txt中

2,1,127
2,4,127
31,3,1431655765
32,3,1431655765

output.txt的

getbits(x=127, p=2, n=1) = 1
ERROR
getbits(x=1431655765, p=31, n=3) = 2
ERROR

我知道这是基本的，但我真的很赞赏任何帮助：）

Answer 1

您还可以在不使用fscanf的情况下从文件中读取整数。以下是一些从文件中读取内容的代码，而不使用fscanf。我还更正了您将int数据与long long进行比较的值的某些数据类型声明。

int main()
{
    FILE * ipf = fopen("input.txt", "r");
    long long x = 0 , p = 0, n = 0, b = 0;
    char * line = NULL;
    size_t len = 0;
    ssize_t read;
    char *token;

      while ((read = getline(&line, &len, ipf)) != -1)
      {   
            token=strtok(line,",");
            p=atoi(token);

            token=strtok(NULL,",");
            n=atoi(token);

            token=strtok(NULL,"");
            x=atoi(token);

            if(x < 4294967296 && p < 32 && n < p + 2)
            { 
              b = getbits(x,p,n);
              printf("gebits( x = %lld, p = %lld, n =  %lld) = %lld\n", x, p, n, b);
            } 
            else { printf("ERROR\n"); }
      }

  return 0;
}

对于Windows，请使用以下解决方案：

int main()
{
    FILE * ipf = fopen("input.txt", "r");
    long long x = 0 , p = 0, n = 0, b = 0;
    char line [256];
    size_t len = 0;
    ssize_t read;
    char *token;

  while ((fgets(line,256, ipf)) != 0)
  {   
        token=strtok(line,",");
        p=atoi(token);

        token=strtok(NULL,",");
        n=atoi(token);

        token=strtok(NULL,"");
        x=atoi(token);

        if(x < 4294967296 && p < 32 && n < p + 2)
        { 
          b = getbits(x,p,n);
          printf("gebits( x = %lld, p = %lld, n =  %lld) = %lld\n", x, p, n, b);
        } 
        else { printf("ERROR\n"); }
  }

  return 0;
}

C从没有fscanf的txt读取整数

1 个答案: