Bash

Watch for file change

tail -f file

Move file/directory

mv /path/to/source /path/to/dest

-v add verbose

for multiple directories (in this case 2 but can be done with more) at once:
mv /path/to/source1 /path/to/source2 -t /path/to/dest
-t is for the target directory to move to

Copy file/directory on/from a remote machine

From remote:

scp user@ip_or_name:/path/to/source/ /path/to/dest

To Remote:

scp /path/to/source/ user@ip_or_name:/path/to/dest

-r for directories
-P for a specific port

Disk Usage

The command du (disk usage) lets you find out how much space is used by files.

Human-readable

-h shows the size of the files in a more human-friendly format (Ko, Mo, Go, To).

Summarize

-s sums the sizes of all the files and subfolders in the given folder.

Limit depth

-d N limits the depth of the output to subfolders of depth N.