c fgets 重复最后一个字符

Question

I am trying to read integer values from stdin. I have a inner while loop that detects integer series so that I can parse ints with multiple characters. I strtok the buffer with newline delimiters because input can have integers over multiple lines.

My code to handle this is:

while (fgets(buf, BUF_SIZE, stdin)) {
    strtok(buf, "\n");
    for(int i = 0; buf[i] != '\0'; i++) {
        size_t j = 0;
        if(isdigit(buf[i])) {
            while(isdigit(buf[i+(int)j])) {
                j++;
            }
            char *new_str = malloc(j*sizeof(char));
            size_t k =0;
            while(k < j) {
                new_str[k] = buf[i+(int)k];
                k++;
            }
            printf("%s\n", new_str);
            free(new_str);
        }
    }
}

The input could be: 1 9 10 10 11

The output should be:

1
9 
10 
10 
11

The output I get is:

1
9
10
0
10
0
11
1

So every last character of input with n>1 gets read twice by the buffer some way.

I am unsure how this is possible but can't figure it out.

Answer 1

This happens because you grow j over the input string but you forget to grow i together with j . So you grow j and after you print it, you will grow i by 1 from the last value, and that i+1 will fall inside the input string that was already printed...

The solution is to reinitialize i so:

        if(isdigit(buf[i])) {
          .....
          free(new_str);
          i = i+j;
        }