linux下的mv mkdir cp tac commands

tac:
  tac [file]
  this command is named as an opposite for the cat command,which simply print text file to standard output.in this case,tac print the text files to standard output with lines in reverse order
  
cp:
  cp [options] file1 file2
  cp [options] file1 directory
  -f force an overwrite of existing files in destination
  -i prompt interactive before override destinations files.
  -p preserve all information.include owner,group,permission.and the timestamps.without the option,the copied file or files will have the present(现在的) date and time.default permission .owner and group
  -r or R recursively copy directories.
  -v display the name of each file verbosely before copying
  
mkdir:
  mkdir [options] directory
  frequence used parameters
   -m mode ;set the access mode for the directory
   -p ;create intervening parent directories if they don't exist
   example create a read-only directory
   mkdir -m 444 ~/ye/directories ;the tidle(~) is shortcut for the home directory.if is the superuser root,the ~ replace the /root,
   mkdir -p ~/dir1/dir2/dir3 ;the directory dir1,dir2,dir3 is not exist before perform the command.
   
mv:
  mv [options] source target
  description:move or rename files and directory.for targets on the different filesystem,such a change can't be made,so files are copyied to the target location and the original sources are deleted.if a target file or directory does not exist.source is rename to target.


example:
 mv files/file ~/home
  if the directory ~/home don't exist. it will create home at the home directory replace the file "files/file". if target is a existing directory. source is moved into that directory.
 -f     force the move even the target exists,suppressint warning message
 -i      query interactive before moving files