Question

如何创建一个打开输入文件并从文件中读取数据的输入函数？该文件是否必须存储在某个位置？我可以将它作为文本文件保存在桌面上吗？这就是我到目前为止所拥有的

#include <stdio.h>  /* NULL is defined here */
#include <stdlib.h> /* for malloc() */
#include <string.h> /* for string related functions */

#define  NAME_LEN  10

struct data {
   char  name[NAME_LEN];
   int   age;
   int   weight;
};

typedef  struct data  DATA;

struct linked_list {
   DATA                d;
   struct linked_list * next;
};

typedef  struct linked_list  ELEMENT;
typedef  ELEMENT *           LINK;

/* function prototypes */
LINK create_list_from_file(const char *);
void print_list_to_file(LINK, const char *, const char *);
int count(LINK, const int, const int);
LINK lookup(const DATA, LINK);
void insert(LINK, LINK, LINK);

nt main(int argc, char *argv[])
{
   LINK head, found, to_add;
   char *in_file_name = "infile";   /* default input file name */
   char *out_file_name = "outfile"; /* default output file name */
   int a = 20, w = 150;  /* will be used as the age limit and weight limit */


   /* The input and output files can be given as command line arguments */ 
   switch (argc) {
   case 1:
      printf("The default input and output files are %s and %s.\n",
              in_file_name, out_file_name);
      break;
   case 2: 
      printf("The input file is %s and the default output file is %s.\n",
              argv[1], out_file_name);
      in_file_name = argv[1]; 
      break;
   case 3:
      printf("The input file is %s and the output file is %s.\n",
              argv[1], argv[2]);
      in_file_name = argv[1]; 
      out_file_name = argv[2];
      break;
   default:
      printf("The input file is %s and the output file is %s.\n",
              argv[1], argv[2]);
      in_file_name = argv[1]; 
      out_file_name = argv[2];
      printf("The remaining arguments are not used.\n");
   }

/*
1. invoke create_list_from_file() function to create a linear linked list 
   from the data in the input file,
*/
   head = create_list_from_file(in_file_name);
/*
2. invoke print_list_to_file() function with the writing mode ("w"),
*/
   print_list_to_file(head, out_file_name, "w");
/*
3. invoke the count() function,
4. output the counted result to the screen,
*/
   printf("The number of people with age over %d and weight over %d is %d.\n", 
           a, w, count(head, a, w));
/*
5. invoke the lookup() function and insert() function, and
*/
   /* prepare an element to be looked-up and added */
   to_add = malloc(sizeof(ELEMENT));
   strcpy(to_add -> d.name, "Janet");
   to_add -> d.age = 21;
   to_add -> d.weight = 150;
   to_add -> next = NULL;

   found = lookup(to_add -> d, head);
   insert(head, found, to_add);
/* 
6. invoke print_list_to_file() function with the append mode ("a").
*/
   print_list_to_file(head, out_file_name, "a");

/* 
repeat step 5 with an element that does not exist in the current list 
*/
   /* prepare an element to be looked-up and added */
   to_add = malloc(sizeof(ELEMENT));
   strcpy(to_add -> d.name, "Jerry");
   to_add -> d.age = 24;
   to_add -> d.weight = 220;
   to_add -> next = NULL;

   found = lookup(to_add -> d, head);
   insert(head, found, to_add);
/* 
repeat step 6: invoke print_list_to_file() function with the append mode ("a").
*/
   print_list_to_file(head, out_file_name, "a");

   return 0;
}

Answer 1

您可以使用标准库打开计算机上的几乎任何文件，包括可访问的网络存储。可以读取文本或二进制文件，包括简单的“.txt”文件。例如，您可以从文件中读取一个整数：

#include <stdio.h>
...
int i;
FILE *f;
f= fopen("D:\Temp\SomeFile.txt", "r");
fscanf(f, "%d", &i);
fclose(f);

如果需要，您可以使用面向行的语义（如上例所示） - look C library reference for fopen等。应该有一些可能有用的示例。

创建输入功能

1 个答案: