从文本文件读取和打印输出

Question

I have to make a program written in C that will read and print out some things in a text file.

But 2 function of the program below wont work for some reason. Case 3 works fine. But the other 2 print nothing or just 1 name. How is this possible and how can I fix this.

I don't get any errors btw.

#include <stdio.h>

main()
{
  FILE *list;
  int number, menu, total;
  char name[20];

  list = fopen("C:\\PATH\\TO\\FILE", "r");

  printf("Menu: \n"\n);
  printf("[1] Positive total: \n");
  printf("[2] Negative total: \n");
  printf("[3] Total: \n");
  printf("[4] Quit \n\n");
  printf("Choose: 1,2,3 or 4:\n");
  scanf("%d", &menu);

 while (menu!=4)
 {
        fscanf(list, "%d%s%d", &number, name, &total);
        switch(menu)
        {
                    case 1: printf("Negative total \n");
                            while(!feof(list))
                            {
                                if (total<0)
                                {
                                      printf("-%6d%-15s%6d\n", number, name , total);
                                      fscanf(list, "%d%s%d", &number, name, &total);
                                }
                            }
                            break;

                    case 2: printf("Positive: \n");
                            while(!feof(list))
                            {
                                if (total>=0)
                                {
                                      printf("-%6d%15s%6d\n", number, name , total);
                                      fscanf(list, "%d%s%d", &number, name, &total);
                                }
                            }
                            break;

                    case 3: printf("Total: \n");
                            while(!feof(list))
                            {
                                printf("-%6d%15s%6d\n", number, name , total);
                                fscanf(list, "%d%s%d", &number, name, &total);
                            }
                            break;
        }

        rewind(list);
        printf("\nChoose again, 1, 2, 3, 4: ");
        scanf("%d", &menu);
        }
        printf("End of Program");
        fclose(list);

        return 0;
}

The text file consist of numbers, names, total money they have (you could see it as a bank system). Here is the text file:

5892 John +7250
5893 Kate -94
5894 Mike +324
5895 Jack +9570
5896 Anne +800

Answer 1

You have an infinite loop condition in both case 1 and 2. In case 1, this:

if (total<0)
{
    printf("-%6d%-15s%6d\n", number, name , total);
    fscanf(list, "%d%s%d", &number, name, &total);
}

Should, instead, be:

if (total<0)
{
      printf("-%6d%15s%6d\n", number, name , total);
}
fscanf(list, "%d%s%d", &number, name, &total);

Otherwise, you will be stuck every time you read a positive amount of money: total will be >= 0, so you don't enter the if block, and you never perform the fscanf() call to keep on reading the file. The loop expects to reach the end of file, but you never reach it because you're not reading forward, you just stopped.

The same happens for case 2: you have to call scanf outside of the if block, like this:

if (total>=0)
{
      printf("-%6d%15s%6d\n", number, name , total);
}
fscanf(list, "%d%s%d", &number, name, &total);

Also, the code you posted doesn't compile on line 11 (you have printf("Menu: \\n"\\n), ie, with a newline out of the string. Please try to provide compilable code in the future.

Here's a working version:

#include <stdio.h>

int main()
{
  FILE *list;
  int number, menu, total;
  char name[20];

  list = fopen("example", "r");

  printf("Menu: \n\n");
  printf("[1] Positive total: \n");
  printf("[2] Negative total: \n");
  printf("[3] Total: \n");
  printf("[4] Quit \n\n");
  printf("Choose: 1,2,3 or 4:\n");
  scanf("%d", &menu);

 while (menu!=4)
 {
        fscanf(list, "%d%s%d", &number, name, &total);
        switch(menu)
        {
                    case 1: printf("Negative total \n");
                            while(!feof(list))
                            {
                                if (total<0)
                                {
                                      printf("-%6d%15s%6d\n", number, name , total);
                                }
                                fscanf(list, "%d%s%d", &number, name, &total);
                            }
                            break;

                    case 2: printf("Positive: \n");
                            while(!feof(list))
                            {
                                if (total>=0)
                                {
                                      printf("-%6d%15s%6d\n", number, name , total);
                                }
                                fscanf(list, "%d%s%d", &number, name, &total);
                            }
                            break;

                    case 3: printf("Total: \n");
                            while(!feof(list))
                            {
                                printf("-%6d%15s%6d\n", number, name , total);
                                fscanf(list, "%d%s%d", &number, name, &total);
                            }
                            break;
        }

        rewind(list);
        printf("\nChoose again, 1, 2, 3, 4: ");
        scanf("%d", &menu);
        }
        printf("End of Program");
        fclose(list);

        return 0;
}

Some final remarks: I would test for fopen()'s return value to make sure the file was successfully opened. You might also want to perform some error checking with ferror() on your loop conditions. Finally, make sure that your "name" buffer is big enough, 20 characters is not very large. For a safe program, you should use fgets(name, 19, stdin) instead, and then null-terminate the string.