1. How should I read in the data?

There are many ways, but I would suggest using fgets to read a line into a single char array. Make a read loop that calls fgets, then calls a function to read the date. Have that function return the integer index where it stopped reading, and pass the index to a function that reads the temperatures, etc.

Now put the whole loop into a function you can call from main(). Put a loop around it to read the whole data file; when that works, put it into a function you can call from main(), so that your whole data reading process is a single call from main().

2. Some of the numeric columns have the word "error" in them. How do I handle this?

See number 1. If you read the whole line in, you can look at the place where you expect a number to be and see if it has "error" there instead. If it does, then put a value in your array that indicates an error. If not, then read the double (sscanf would be good here) into your data array.

3. How do I copy the file?

You could get the file using your browser and the "save as" button, but since it is on a disk that the composer's use, you can just copy it:

cp /www/htdocs/CIS/105/tharvey/06F/projects/project2/wilm0110temperatures.csv temps.csv

After you copy or save the file into your directory, open it with emacs and make sure that it ends with a newline, and save.

4. Can I make another array to temporarily hold a line of text thta I read in with fgets()?

Yes.