Converting a string timestamp HH:MM:SS to an integer in C

Question

Forgive me for my naivety I'm just learning C for the first time. Basically I have a series of strings that contain a timestamp in the format "HH:MM:SS". I'm looking to write a function of the form int tsconvert(char *) that can covert the timestamp to an integer. Here is some code I've written so far

int tsconvert(char *timestamp)
{
    int x;
    removeColon(timestamp,8);
    x = atoi(timestamp);
    return x; 
}

void removeColon(char *str1, int len)    
{
    int j = 0;
    for (int i = 0; i < len; i++)
    {
        if (str1[i] == ':')
        {
            continue;
        }

        else
        {
            str1[j] = str1[i];
            j++;
        }
    }

    str1[j] = '\0';
}

When I try and use this code however I get a segmentation error. Some one in my programing class suggested that I simply extract the numbers from the timestamp and place those in a new string but I'm not sure how to do that.

Answer 1

To extract the numbers from the timestamp (HH:MM:SS), just use sscanf():

const char *str = "01:02:03";
int h, m, s;
sscanf(str, "%d:%d:%d", &h, &m, &s);
printf ("%d, %d, %d\n", h, m, s);

Answer 2

My suggestion is not much different than @Younggun Kim but with recommended additional error checking.

Use "%n" to determine if scanning completed to the end of the string with no additional junk.

// -1 error else 0 - 86399
long tsconvert(const char *timestam) {
  unsigned h, m, s;
  int n = 0;
  int cnt = sscanf(timestam, "%2u:%2u:%2u %n", &h, &m, &s, &n);
  if (cnt != 3 || timestam[n] != '\0') return -1 ; // Format Error;
  if (h >= 24 || m >= 60 || s >= 60) return -1; // Range Error
  // 0 - 86400-1
  return ((h*60 + m)*60L + s;
}