Question

我们有一个赋值，即从文件中获取字符，将给定值向右移动（它在代码中有意义），然后将新值存储在新文件中，但我似乎遇到分段故障，据我所知，这意味着我试图访问我已经分配的内存之外的内存？我是C的新手，我设法调试此代码直到这一点，老实说，我不知道该去哪里。我甚至不太明白这个问题是什么。

#include<stdio.h>
//Get Shift amount
//Get ifilename
//Get ofilename
//open them
//Get characters one at a time from input
//Process and shift by shift amount
int main()
{
    int i;//loop value
    char a[62]="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";//Variable with every value
    int sa = 0;//Store Shift value
    char ofile[30];//contain the name of output file
    char ifile[30];//contain name of input file
    char value;//Value to keep the current value in

    printf("How far in ascii values would you like to shift?\n");
    scanf("%i", sa);//Get shift
    printf("What is the name of your input file located in this directory?");
    scanf("%s", ifile);//get input name
    printf("What would you like to name your new file?\n Do note that it will overwrite the current file named this!");
    scanf("%s", ofile);//Get output name

    FILE *oIfile = fopen(ifile, "r"), *oOfile = fopen(ofile, "w");

    while(value = fscanf(oIfile, "%c", value) != EOF)//Check to ensure that you never reach the end of the file
    {
        for(i=0; i<62; i++)//loop through the list of all characters
        {
            if(value == a[i])//check to see if the value from the input file matches with which letter
            {
                value = a[i+sa] % 62;//incrase the value by the shift amount, check if its longer than 62, add remainder
                break;//break the for loop so we can restart the while loop with the next letter
            }
        }
        fprintf(oOfile, "%c");//print the new value to the output file
    }
    fclose(oIfile);//close input file
    fclose(oOfile);//close output file
}

由于我的scanf方法，

是这个问题吗？

Answer 1

除了将地址传递给你必须做的scanf (scanf("%i",&sa)之外（检查它的返回值也是正确的） - 你需要纠正一些事情： - < / p>

应该是(value = fscanf(oIfile, "%c", value)) != EOF。 !=的优先级高于=，因此需要获得正确的结果。
同样a[(i+sa)%62]=...是正确的做事方式。因为否则它将访问某些sa值导致未定义行为的数组索引超出范围。
fprintf(stream,"%c",charvariable)这将用于fprintf。
value覆盖了fscanf返回的值返回的内容。您应该使用其他临时变量，或者甚至更好地使用此while(fscanf(oIfile, "%c", value)!=EOF)。但要获得更多支票，你需要做点什么，比如
```
  int c;
  while((c=fscanf(oIfile, "%c", value))!=EOF)
```

通过在sa中传递scanf的值而非其地址，您在此处出现了细分错误。

Answer 2

scanf将地址作为参数。试试这个;

scanf("%i", &sa);//Get shift

分段错误，scanf

2 个答案: