Short for "change directory".
The shorthand name for the current directory is .
The shorthand name for the parent directory is ..
present working directory
list the contents of the present directory
mkdir <directory> //<directory> is the represent for the name of the directory
Short for "make directory",this command will create a new subdirectory called <directory> located in the current directory
cp <source> <destination> // 仅复制单个文件，不能复制文件夹
Short for "copy",this command will allow you to create a duplicate of the file you specify as <source>,whichi it will save in <destination>
eg. cp hello.c hi.c // copy hello.c and rename the copyfile as hi.c in the present directory
-r <directory> <destinction> //加了参数 -r 表示复制文件夹
Short for "recursive",copy the directory recursively.copy the <directory> and copy every folder that exists inside of it and every file that exists inside of it.In other words, It need to recursively dive down into <destincton> and make a copy of everything in there
rm <file> // 仅删除单个文件，不能删除文件夹
Short for "remove",this command will delete<file> after it asks you to confirm (y/n) you want to delete it.
Short for "force",foce rm to do exactly what we‘re telling it to do.
but use at your own peri!there‘s no undo.
to delete entire directories you need to use the -r flag,just as was the case with cp.
combine the -r and -f flags into -rf .Again,careful!There‘s no undo!
mv // 移动文件
Short for "move",this command will allow you to effectively rename a file,moving it from <source> to <destination>.
Rename Source to DEST,or move SOURCE(s)to DIRECTORY.
problem: su command cannot use
sudo passwd // set root password;and then you can use su command