These are some useful Linux Terminal Commands for productivity:

Commands using ls etc.

use to
ls -ltr list files in reverse modification history order with details.
`ls -ltr tail -n 5`
`ls head -n 5`
rename 's/original/new/' * To rename all filenames and directories containing “original” string to “new” string. To recursively do this in sub-directories, use **/*. See: here and here
for dir in */; do mkdir -- "$dir"/{tmp1,foo,bar,qux}; done To create directories within sub-directories in one go!

For opening image files from Terminal

Opening files directly through the Terminal is both easy and fast. Additionally, these commands are useful to view resulting files when using subprocess.run in Python to run Terminal commands.

use to
evince filename open PDF files and PS document files.
eog filename open image files in normal image formats like JPEG, JPG, PNG etc.
ds9 filename open FITS format image files. Requires DS9
fv filename open FITS format event lists and datasets. Requires initiation of NASA’s heasarc