Unix command to trim file contents

Question

can someone help me with the unix command to trim the contents of files in a directory. I use Cygwin in windows.

Answer 1

for file in * do >$file done 

Answer 2

Just redirect from nowhere:

 > somefile.txt 

Answer 3

If you want to truncate the file in order to save the n last lines of the file, you can do something like (500 lines in this example)

 mv file file.tmp && tail -n 500 file.tmp > file && rm file.tmp