Scenario 1
The commands are simply saved as a list to the ~/.bash_history file. this is a hidden file (Begins with .), in your home directory (~). You can view the history of commands run by running history, which is similar to cat -n ~/.bash_history, except the latter does not include commands from the current running terminal session, as those are saved when the terminal closes. Here is the manual page for history:
history [n]
history -c
history -d offset
history -anrw [filename]
history -p arg [arg ...]
history -s arg [arg ...]
With no options, display the command history list with line num‐
bers. Lines listed with a * have been modified. An argument of
n lists only the last n lines. If the shell variable HISTTIME‐
FORMAT is set and not null, it is used as a format string for
strftime(3) to display the time stamp associated with each dis‐
played history entry. No intervening blank is printed between
the formatted time stamp and the history line. If filename is
supplied, it is used as the name of the history file; if not,
the value of HISTFILE is used. Options, if supplied, have the
following meanings:
-c Clear the history list by deleting all the entries.
-d offset
Delete the history entry at position offset.
-a Append the ``new'' history lines (history lines entered
since the beginning of the current bash session) to the
history file.
-n Read the history lines not already read from the history
file into the current history list. These are lines
appended to the history file since the beginning of the
current bash session.
-r Read the contents of the history file and use them as the
current history.
-w Write the current history to the history file, overwrit‐
ing the history file's contents.
-p Perform history substitution on the following args and
display the result on the standard output. Does not
store the results in the history list. Each arg must be
quoted to disable normal history expansion.
-s Store the args in the history list as a single entry.
The last command in the history list is removed before
the args are added.
If the HISTTIMEFORMAT variable is set, the time stamp informa‐
tion associated with each history entry is written to the his‐
tory file, marked with the history comment character. When the
history file is read, lines beginning with the history comment
character followed immediately by a digit are interpreted as
timestamps for the previous history line. The return value is 0
unless an invalid option is encountered, an error occurs while
reading or writing the history file, an invalid offset is sup‐
plied as an argument to -d, or the history expansion supplied as
an argument to -p fails.
Scenario 2
Dunno where that would be - Document Viewer - evince - has config files in ~/.config/evince, but nothing seems useful there. There is a local cache directory - ~/.cache - where it could be...
For the current session on the computer, temporary storage (Like opening compressed files in Archive Manager) is done in /tmp, and is cleared on shutdown. More permanent storage (e.g. file thumbnails for the File Broweser) is stored in ~/.cache, and hidden files in the home directory ~/.*.
