BASH and Octave

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One of the nice features of Octave (and similar languages) is that you don't have to compile the code that you generate. It is interpreted by Octave instead. This make learning the language easy by trial-and-error. Very often it is useful to save what you have learned from you fiddlings during the current Octave 'session' that you have opened for this fiddling. Octave keeps a copy of all your command you give on the Octave command line. In Linux it is saved in the file ~/.octave_hist.

If you want to save all the Octave commands you gave during the last Octave session, generate a file octave_save_last_session in your directory ~/bin and put the following inside: (that is: you have to open a terminal on your Linux computer and type the following commands on the terminal command line (make sure it is the BASH shell).

#!/bin/bash                                                                                                                                                                                 
filename='octave_save_last_session.m'
if [[ $# -eq 1 ]] ; then
        filename=$1
fi
 
tac $HOME/.octave_hist | awk '/^#/ {found++} ; found<2 ' |tac >$filename

Then you still need to tell the BASH shell to make this file ~/bin/octave_save_last_session executable:

chmod u+x ~/bin/octave_save_last_session

Now, imaging you have 'played around' in an interactive Octave session to try/test something: you want to save the commands you just used to not-forget. Just close the Octave session. If (in Linux) you close Octave that you have started from the command line, you will automatically return to the command line. Now you want to have a seperate copy of your last session put in a file (a *.m file). On the command line, you just type octave_save_last_session, and the last session (only!) is copied from the ~/.octave_hist file and saved to octave_save_last_session.m. You can edit that file to remove parts you don't want to save, or you can re-execute the commands by octave --persist octave_save_last_session.m.