如何从文件中读取一行？

Question

I have to read a txt file with lines formated like this:

1: (G, 2), (F, 3)
2: (G, 2), (F, 3)
3: (F, 4), (G, 5)
4: (F, 4), (G, 5)
5: (F, 6), (c, w)
6: (p, f), (G, 7)
7: (G, 7), (G, 7)
w: (c, w), (c, w)

Each line will feed a struct with its data (the 5 numbers or letters in it).
What's the best way to read the line and get the strings I want?
I'm currently using a long sequence of conditions using fgetc but that seems ugly and not very smart.
I can't use arrays because the lines may vary in size if the numbers have two digits.

Answer 1

我想你可以解析它：

fscanf(file,"%c: (%c, %c), (%c, %c)", &first,&second,&third,&fourth,&fifth);

Answer 2

Use fgets() :

#include <stdio.h>

int main(void)
{
  char line[256];
  while(fgets(line, sizeof(line), stdin) != NULL)  // fgets returns NULL on EOF
  {
    // process line; line is guaranteed to be null-terminated, but it might not end in a
    // newline character '\n' if the line was longer than the buffer size (in this case,
    // 256 characters)
  }

  return 0;
}

Answer 3

#include <stdio.h>

int main (void)
{
  char buf[81];       /* Support lines up to 80 characters */
  char parts[5][11];  /* Support up to 10 characters in each part */

  while (fgets(buf, sizeof(buf), stdin) != NULL)
  {
    if (sscanf(buf, "%10[^:]: (%10[^,], %10[^)]), (%10[^,], %10[^)])",
               parts[0], parts[1], parts[2], parts[3], parts[4]) == 5)
    {
      printf("parts: %s, %s, %s, %s, %s\n",
             parts[0], parts[1], parts[2], parts[3], parts[4]);
    }
    else
    {
      printf("Invalid input: %s", buf);
    }
  }
  return 0;
}

Sample run:

$ ./test
1: (G, 2), (F, 3)
2: (G, 2), (F, 3)
3: (F, 4), (G, 5)
4: (F, 4), (G, 5)
5: (F, 6), (c, w)
6: (p, f), (G, 7)
7: (G, 7), (G, 7)
w: (c, w), (c, w)
parts: 1, G, 2, F, 3
parts: 2, G, 2, F, 3
parts: 3, F, 4, G, 5
parts: 4, F, 4, G, 5
parts: 5, F, 6, c, w
parts: 6, p, f, G, 7
parts: 7, G, 7, G, 7
parts: w, c, w, c, w

If the last value in the input is more than 10 characters it will be truncated with no indication of error, if this is not acceptable you can use the %c conversion specifier as a sixth argument to capture the next character after the last value and make sure it is a closing parenthesis.

Answer 4

我记得fgets（）和sscanf（）

Answer 5

fscanf works pretty nice, but you'll have to use string conversions, because chars wouldn't work for numbers with more than one digit.

Isn't this some kind of homework?

#include <stdio.h>

void main(int argc, char **argv) {
    FILE * f;
    f = fopen(argv[1], "r");

    while (1) {
        char char_or_num[32][5]; // five string arrays, up to 32 chars
        int i;
        int did_read;

        did_read = fscanf(f, "%32[0-9a-zA-Z]: (%32[0-9a-zA-Z], %32[0-9a-zA-Z]), (%32[0-9a-zA-Z], %32[0-9a-zA-Z])\n", char_or_num[0], char_or_num[1], char_or_num[2], char_or_num[3], char_or_num[4]);
        if (did_read != 5) {
            break;
        }
        printf("%s, %s, %s, %s, %s\n", char_or_num[0], char_or_num[1], char_or_num[2], char_or_num[3], char_or_num[4]);
    }

    fclose(f);
}

Answer 6

#include
void
f()
{
    FILE* fp;

    if ( (fp = fopen("foo.txt", "r")) == NULL)
    {
        perror("fopen");
        return;
    }

    char ch[5];
    while (fscanf(fp, "%c: (%c, %c), (%c, %c)\n", &ch[0], &ch[1], &ch[2], &ch[3], &ch[4]) == 5)
    {
        printf("--> %c %c %c %c %c\n", ch[0], ch[1], ch[2], ch[3], ch[4]);
    }

fclose(fp);
}

Answer 7

基本上你必须通过fgetpos保存文件ptr的位置，走到行的末尾（但是你定义它），保存那个大小，fsetpos到前一个位置，分配一个足够大的缓冲区来保存行，然后使用新缓冲区调用fread。

Answer 8

Assuming you have the correct variables, this should work:

 fscanf(fp, "%[^:]: (%[^,], %[^)]), (%[^,], %[^)])", a, b, c, d, e);

fp is a file pointer and "a" to "e" are char pointers