How to invoke octave script in unix shell

Yes, of course you can write an Octave program. Like so:

$ cat octave_program 
#!/usr/bin/env octave
## Never forget your licence at the top of the files.
1;

function [rv] = main (argv)
  disp ("hello world");
  rv = 0;
  return;
endfunction

main (argv);

$ chmod a+x octave_program # add executable permissions
$ ./octave_program 
hello world

There's a couple of things important for an Octave program:

1. the first statement cannot be a function declaration. In all my programs, the first statements are loading of necessary packages. If you don't have packages, it is common to use 1;

2. a she-bang line. That's the first line of your program which tells you how to run your program. If you know where Octave will be installed, you can use #!/usr/bin/octave but using #!/usr/bin/env octave will be more portable and flexible.

3. your program needs executable permissions