You can use ''file'' command available on linux to see the type of the file. sometimes, when you download a file, the file may have been expanded. in my case, i was downloading a ps.gz file. but i could not use gunzip to expand it at last, i was told to use ''file'' to detect the type of the file disregarding the suffix, then it ended up with finding out the file actually has been expanded. but the stupid windows application did not change its name accordingly. so i had to change the suffix by f