Question

I need parse through a file and do some processing into it. The file is a text file and the data is a variable length data of the form “PP1004181350D001002003……….”. So there will be timestamps if there is PP so 1004181350 is 2010-04-18 13:50. The ones where there are D are the data points that are three separate data each three digits long, so D001002003 has three coordonates of 001, 002 and 003.

Now I need to parse this data from a file for which I need to store each timestamp into a array and the corresponding datas into arrays that has as many rows as the number of data and three rows for each co-ordinate. The end array might be like

TimeStamp[1] = "135000", low[1] = "001", medium[1] = "002", high[1] = "003"
TimeStamp[2] = "135015", low[2] = "010", medium[2] = "012", high[2] = "013"
TimeStamp[3] = "135030", low[3] = "051", medium[3] = "052", high[3] = "043"
....

The question is how do I go about doing this in C? How do I go through this string looking for these patterns and storing the values in the corresponding arrays for further processing?

Note: Here the seconds value in timestamp is added on our own as it is known at each data comes after 15 seconds.

Answer 1

edit: updated to follow your specs.

While your file seems to be variable length, your data isn’t, you could use fscanf and do something like this:

while(fscanf(file,"PP%*6d%4d", &timestamp, &low, &medium, &high)) 
{
    for(int i = 0; fscanf(file, "D%3d%3d%3d", &low, &medium, &high); i++)
    {
        timestamp=timestamp*100+i*15;
        //Do something with variables (e.g. convert to string, push into vector, ...)
    }
}

Note that this reads the data into integers (timestamp, low, medium and high are int’s), A string version looks like this (timestamp, low, medium and high are char arrays):

int first[] = {'0', '1', '3', '4'};
int second[] = {'0','5'};

while(fscanf(file,"PP%*6d%4c", &timestamp, &low, &medium, &high)) 
{
    for(int i = 0; fscanf(file, "D%3c%3c%3c", &low, &medium, &high); i++)
    {
        timestamp[i][4]=first[i%4];
        timestamp[i][2]=second[i%2];
    }
}

edit: some more explanation about the formatting string, with %*6d I mean: look for 6 digits and discard them (* means: do not put in a variable). %4d or %4c means in this context the same (as 1 digit will be one char), but we do save them in corresponding variables.