I am using midnight commander. To view the content of a .txt file I press F3. Then I can select text holding Shift + selecting with mouse:
But I would like to select the whole content of the file and it is not possible to scroll while I am selecting with the mouse.
Is there a "select all" option in that View mode?
Midnight Commander cannot do it. You may want to file a feature request here: https://midnight-commander.org/wiki/NewTicket
Please use any graphical text editor instead.
On a second thought I don't believe it's technically possible. MC disables scrolling which means your terminal must and must not have a scrolling history at the same time. You cannot select less output which spans more than a single screen either.
smcup/rmcup (ti/te) cursor-addressing mode, which generally switches to alternate screen (and that disables "scrolling"). But selecting a whole file would have to be done using new code in MC (unrelated to shifted-mouse selection), since the whole file is not on the terminal's screen/scrollback. Most likely the best you could do is to put command cat a.txt in your terminal and then select trxt yoy need using mouse directly in terminal. Afaik, mcview does not support functionality you need
