rm
rm [options] files -d remove directory even if they are not empty.the option is reserved(保留，预定)for privilege users -f force removal of write-protected files without prompting -i query interactive before removing files -r -R if the files is a directory,recursively remove the entire directory and all of its contents,include subdirectories
the parameter -d ,I can't test success.
rmdir rmdir [options] directories delete directories ,which must be empty -p remove directories and any intervening(插入，干涉，干预) parent directories that become empty as a result.
touch touch [options] files change the access and/or modification times of files. -a change only the access time -m change only the modification time -t timestamp ;instead of the current time,use timestamp in the form of [[cc]yy]MMDDhhmm[.ss],for example,the timestamp for january 12,2001,at 6:45 p.m is 200101121845
pipes this is accomplished using a pipe(|) to join two or more commands together.for example: grep "01254" order*|less this command searches through all files whose names begin with order to find lines contains the word 01254.
