how to read specific input format

Question

i am supposed to read input from stdin in format like "%c %d:%d:%d %d" and allowed character at the beginning are + - #

what i have tried is

while(1){       
    ret = scanf(" %c %d:%d:%d %d",&c,&h,&m,&s,&id);
    if (ret != 5) break;

        if(c=='#') {
            log++;
            abs_prev=-1;
            continue;
        }else if(c=='+'){}
        else if(c=='-'){}
        else{
            printf("invalid input.\n");
            return 0;
        }
}

this code fails because when i enter input + 15:00:00 1enterbutton#enterbutton it puts \n character into the variable c which is not matched below and returns 0

here is what my input can look like + 8:00:00 100 + 8:50:00 105 - 9:30:00 100 - 18:20:00 105 - 19:00:00 100 # - 17:00:00 100 + 18:00:00 100 # # + 8:00:00 66 + 9:00:00 200 + 10:00:00 100 - 15:00:00 200 - 17:30:00 66

what i want to do with it is when first char is + i store data in tree A, if its - i will store it in tree B when its # i create new tree

You can change your scanf() as scanf(" %c %d:%d:%d %d %*c",&c,&h,&m,&s,&id); — Gopi
– Gopi, Commented Nov 23, 2014 at 17:05
ret = scanf(" %c %d:%d:%d %d",&c,&h,&m,&s,&id); ?. What is data type of ret ? — Shravan40
– Shravan40, Commented Nov 26, 2014 at 7:31

chux · Accepted Answer · 2014-11-26 18:34:24Z

1

Read user input with fgets(), then scan it.

char buf[100];
if (fgets(buf, sizeof buf, stdin) == NULL)
  Handle_EOF();

// Note spaces before %d are not needed
int ret = scanf(" %c%d:%d:%d%d", &c, &h, &m, &s, &id);
if (ret == 1) {
  if (c != '#')
    Handle_InvalidInput();
  log++;
  abs_prev = -1;
} else if (ret == 5) {
  if (c != '+' && c != '-') {
    printf("invalid input.\n");
    return 0;
  }
} else {
  Handle_InvalidInput();
}

answered Nov 26, 2014 at 18:34

chux

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Simon Woo · Accepted Answer · 2014-11-26 08:55:20Z

1

You'd better to restructure your code since the input lines can be in different formats. The following code seems to be work for your purpose:

while (1){
    if (scanf(" %c", &c) != 1) break;

    if (c=='#') {
        log++;
        abs_prev=-1;
        continue;
    }

    ret = scanf("%d:%d:%d %d",&h,&m,&s,&id);
    if (ret != 4) break;

    if (c == '+') {}
    else if (c == '-') {}
    else {
        printf("invalid input.\n");
        return 0;
    }
}

Please be sure that the type of c should be char not an integer since its address is passed as an argument of scanf.

edited Nov 26, 2014 at 8:55

answered Nov 26, 2014 at 7:24

Simon Woo

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