Splitting one large file into many if the text in a column doesn't match the text in the one before it

Question

I searched for awhile and couldn\'t find a response to this. I have a standard tsv file with the following format:

1    100    101    350    A
1    101    102            


        

Answer 1

So using grep, something like:

for L in `grep -oE '[A-Z]+$'|uniq|sort|uniq`
do
grep -E ${L}'$' > file.${L}.txt
done 

The phrase grep -oE '[A-Z]+$'|uniq|sort|uniq should find all the unique keys, which you then use to re-parse the file multiple times. The sequence uniq|sort|uniq is to reduce the input to sort.

If you really need to do it in a single pass, then you could process each line, and append it immediately to the appropriate output file.