Please do not create new threads if one already exists. As already said and confirmed by Jaap, seq.puts() will add new line character automatically. You just need to pass the string you want to write to the file.
e.g. Lets write item code and description from tcibd001 to a file.
filename = creat.tmp.file$( bse.tmp.dir$() ) |# Create temp file
fp = seq.open(filename,"w+") |# Open temp file
select tcibd001.item, tcibd001.dsca
str = tcibd001.item & "," & tcibd001.dsca |# Item Code , Description
seq.puts(str,fp) |# Write to file
seq.close(fp) |# Close file
This should create and write the item code and description with comma separator the the output file in bse\temp directory. Each item will be written to a new line.