数据单独读取 fscanf

Question

我正在尝试从文件中读取数字。文件格式如下：

2 4 5 7
3 2 4 7

我尝试使用fscanf 收集所有数字到换行符并将数字存储在一个数组中，与第二行相同。但直接从第二行开始不会再次开始并将其存储在另一个数组中。是否可以使用fscanf 做到这一点？

int main(void)
{
    FILE* fp;
    int *vec = malloc(sizeof(int)*6);
    int *vec_2 = malloc(sizeof(int)*6);
    int row, i;

    fp = fopen("vector.txt","r");

    for(i = 0; i < row; i++) //I don't know how to read until newline
        fscanf(fp, "%d", &vec[k]); //here store the first row in the array

    for(i = 0; i < row; i++)
       fscanf(fp, "%d", &vec_2[i]); //start reading here from the second row

    free(vec);
    free(vec_2);
    return 0;
}

Answer 1

int main(void){
    FILE* fp;
    int cols = 6;
    int *vec_1 = malloc(sizeof(int)*cols);
    int *vec_2 = malloc(sizeof(int)*cols);
    int i, i1, i2;
    char ch;

    fp = fopen("vector.txt","r");

    for(i1 = 0; i1 < cols; ){
        fscanf(fp, "%d%c", &vec_1[i1++], &ch);//Format is limited. "num[ \t\n]"
        if(ch == '\n')
            break;
    }

    i2 = 0;
    while(1==fscanf(fp, "%d", &vec_2[i2])){
        if(++i2 == cols)
            break;
    }
    fclose(fp);
    printf("first  : ");
    for(i=0; i<i1; ++i)
        printf("%d ", vec_1[i]);
    printf("\n");
    printf("second : ");
    for(i=0; i<i2; ++i)
        printf("%d ", vec_2[i]);
    printf("\n");
    free(vec_1);
    free(vec_2);
    return 0;
}

Answer 2

任何时候数据都存储在行中，最好考虑fgets()。

此解决方案适应 N 行和用户可选择的列宽

#define MAX_INT_WIDTH (sizeof (int) * CHAR_BIT/3 + 3)

int **Read_Lines_Of_Numbers(FILE* inf, size_t Expected_Row_Width) {
  int **Row = NULL;
  size_t RowCount = 0;
  size_t RowSize = 0;
  char buf[Expected_Row_Width * (MAX_INT_WIDTH + 1) + 2];
  while (fgets(buf, sizeof buf, inf) != NULL) {
    if (RowCount >= RowSize) {
      RowSize = (RowSize + 1) * 2; // Double size
      Row = realloc(Row, RowSize * sizeof *Row);  // OOM checking omitted
    }
    Row[RowCount] = calloc(Expected_Row_Width, sizeof *Row[RowCount]); // OOM checking omitted
    size_t i;
    char *p = buf;
    for (i = 0; i < Expected_Row_Width; i++) {
      int n;
      if (sscanf(p, "%d %n", &Row[RowCount][i], &n) != 1)
        break;
      p += n;
    }
    if (*p || i != Expected_Row_Width) { // Bad data on line
      free(Row);
      return NULL;
    }
    RowCount++;
  }
  Row = realloc(Row, (RowCount + 1) * sizeof *Row);  // OOM checking omitted
  Row[RowCount] = NULL;
  return Row;
}

int main(void) {
  FILE *inf = fopen("c:/tmp/vector.txt", "r");
  size_t Width = 4;
  int **Data = Read_Lines_Of_Numbers(inf, Width);
  fclose(inf);

  if (Data) {
    size_t i;
    for (i = 0; Data[i]; i++) {
      size_t j;
      for (j = 0; j < Width; j++) {
        printf(" %d", Data[i][j]);
      }
      fputc('\n', stdout);
    }
    free(Data);
  }
  return 0;
}

Answer 3

row 必须初始化为 6 并且可能 col 也可能，您可以使用以下二维数组。

int main()
{
    FILE* fp;
    int **vec;
    int row = 6, col = 6, i, j;
    vec = malloc(sizeof(int *)*row); // allocates space for each row
    for (i = 0; i < row; i++) {
     vec[i] = malloc(sizeof(int)*col); // now allocate space for each cell within a row
    }
    fp = fopen("vector.txt","r");

    for(i = 0; i < row; i++) {
     for (j=0; j < col; j++) {
       fscanf(fp, "%d", &vec[i][j]); // read ith row, jth col
     }
    }

    vec = malloc(sizeof(int *)*row);
    for (i = 0; i < row; i++) {
       free(vec[i]);
    }    
    free(vec);
    return 0;
}