Strange behavior on fresh Debian installation

[Linux for blind general discussion]

On Mon, 4 Feb 2019, Linux for blind general discussion wrote:

> I'm having strange behaviour on fresh install of Debian 9
> After I login and work for  a while then any command on bash terminal is
> missing with message such as the following
> bash: ls command not found

You're not bumping the capslock by any chance?

If not, run:

echo $PATH

(note PATH in all capitals)

to make sure that your search path hasn't changed.  It should include 
/usr/bin and /bin and ideally /usr/local/bin.  Root should also have 
/usr/sbin and /sbin.

HTH,
Geoff.