I really didn't find how to do this and I'm starting to thinks it just can't be done in tsql. However I solved for my specific problem redirecting the stdin and stdout. I use a bash script like this:
tsql connection parameters < tsql_input.sql > tsql_output.csv
lines=`cat tsql_output.csv | wc -l`
# The output includes the header info of tsql and the "(n number of rows)" message
# so I use a combination of head and tail to select the lines I need
headvar=$((lines-2))
tailvar=$((lines-8))
head -$headvar tsql_output.csv | tail -$tailvar tsql_output.csv > new_output_file.csv
And that saves just the query result on 'new_output_file.csv'