I extracted a list of files in a directory with the command ls . However this is not my computer, so the ls functionality has been revamped so that it gives the filesizes in front like this :
This is the output of ls command : I stored the output in a file filelist
When shell encounters a redirection operator > the file will be truncated first (0 byte size) and then opened for writing, so after the redirection file is opened for writing, then shell starts test.awk process. This is the reason why you get a blank output file.
But in case of append >> the previous data is retained and then shell starts test.awk process. This is the reason why the data gets appended.