-h --help give this help
-k --keepdate keep output file date [这里指时间]
-q --quiet quiet mode, suppress all warnings
always on in stdin->stdout mode
-V --version display version number
-c --convmode conversion mode
convmode ASCII, 7bit, ISO, default to ASCII
-o --oldfile write to old file
file ... files to convert in old file mode
-n --newfile write to new file
infile original file in new file mode
outfile output file in new file mode