Question

I’m trying to analyze an enormous text file (1.6GB), whose data lines look like this:

20090118025859 -2.400000 78.100000 1023.200000 0.000000
20090118025900 -2.500000 78.100000 1023.200000 0.000000
20090118025901 -2.400000 78.100000 1023.200000 0.000000

I don’t even know how many lines there are. But I’m trying to split the file by date. The left number is a time stamp (these lines for example are from 2009, january 18th).
How can I split this file into pieces according to the date?

The number of entries per date differs, so using split with a constant number won’t work.
Everything I know would be to grep file '20090118*' > data20090118.dat , but there sure is a way to do all the dates at once, right?

Thanks in advance,
Alex

Answer 1

Using awk:

awk '{print  > "data"substr($1,0,8)".dat"}' myfile