Question

I am working on an assignment that deals with reading data from a text file, and parsing that data to various arrays. For example, a portion of my text file looks as follows:

arbrick  pts/26       141.219.210.189  Thu Mar 29 11:23 - 11:24  (00:00)    
rjmcnama pts/27       141.219.205.107  Thu Mar 29 11:02   still logged in   
ajhoekst pts/26       99.156.215.40    Thu Mar 29 10:59 - 11:08  (00:08)    
eacarter pts/31       141.219.162.145  Thu Mar 29 10:50 - 10:51  (00:00)    
kmcolema pts/31       141.219.214.128  Thu Mar 29 09:44 - 09:47  (00:03) 

I need to parse the data into the following arrays: user id, terminal, ip address, and event times. How can I do this considering that there isn’t a consistant amount of white space between the columns?

EDIT:
I tried using the suggestion that Thiruvalluvar provided, but I just could not get it to work. However, I did switch to sscanf and that is working quite well almost…

while(!feof(myfile)) {
        fgets(buffer, 256, myfile);
        sscanf(buffer, "%s %s %s %s", user_id[i], terminal_id[i], ip_addr[i], events[i]);
    } /*End while not EOF*/

What is working, is the user_id, terminal_id, and ip_addr arrays. However, the events array isn’t working perfectly as of yet. Since the events array is a string that contains white space, how can I use sscanf to add the remainder of the buffer to the events array?

Answer 1

I think, the real part of the question is how to strore them in only 4 arrays. E.g.:

arbrick  pts/26       141.219.210.189  Thu Mar 29 11:23 - 11:24  (00:00)    

Tokenizing this line with whitespace is goin to give many strings. But we are only interested in splitting the entire line into only 4 lines, not more than that.

Solution:

1. Read the line using fgets().

2. Tokenize it using strtok() or strtok_r() (for thread-safe) with whitespace as delimiter.

3. Read the 1st 3 strings into the arrays: user_id, terminal_id and ip_address

4. Store ( and append) the rest of strings into the array events.

   int i = 0;    
   int line_index = 0;     
   char *p;    
   while(...) //loop to read the file
   {
       fgets(line);
       p = strtok(line, " ");
       i=0;
   
       while(p!=NULL)
       {
   
           if(i==0) strcpy(user_id[line_index], p);
   
           if(i==1) strcpy(terminal_id[line_index], p);
   
           if(i==2) strcpy(ip_addr[line_index], p);
   
           else     strcat(events[line_index], p); //anything else goes into array events
   
           i++;
   
       }
   
       line_index++;
   } //end of file-reading loop.