Read/Write/Execute a file

$ chmod +rwx App
$ ./App

Remove

$ rm namefile
$ rm -d Directory
$ rm -rf Directory_with_files

Copy file to a folder

$ cp namefile Downloads
$ ls
namefile  Desktop  Documents  Downloads  Music  Pictures  Public  Templates  Videos
$ cd Downloads
~/Downloads$ ls
namefile

Create empty file

$ touch namefile
$ touch --help

Show in the terminal the file

$ cat namefile
$ cat --help

Create new directory

$ mkdir name
$ mkdir --help

list files from directory

$ ls
Desktop  Documents  Downloads  Music  Pictures  Public  Templates  Videos
$ ls --help

Mounting a RAM drive

$ mount -t tmpfs -o size=5G,nr_inodes=5k,mode=700 tmpfs /tmp

Visudo

sudo visudo

username ALL=(ALL) NOPASSWD:/sbin/restart whatever

Display the amount of available disk space

df
df -h   # human-readable format
df -a   # all filesystems

Display disk usage

du
du -hsx * | sort -rh | head -10    # largest 10 folders

Answer yes in a bash script

yes | /your/command