Question

I am developing a bison program and need to have a last option that allow it to recognize anything. Much like a else if…

Thanks

commands: F{
            t[top++] = 'F';
            }
      |PLUS{
            t[top++] = '+';
            }
      |MINUS{
            t[topo++] = '-';
            }
      |ACOL { 
            t[top++] = '[';
            }
      |FCOL{
            t[top++] = ']';
            }
      |POINT{
             t[top++] = '.';
            }
      |EQUAL {
            t[top++] = '=';
            }
      | {  
           /* generic command should be here
           if any of the commands above were found it should run whatever is here*/
      }

Answer 1

Attach the logic that you want to run after any command token has been recognized in a marker non-terminal, like the following. Notice that the right side of marker‘s production doesn’t match any tokens.

command_and_marker: command marker;

command:  F
            {
            t[top++] = 'F';
            }
        | PLUS
            {
            t[top++] = '+';
            }
        | MINUS
            {
            t[topo++] = '-';
            }
        | ACOL
            { 
            t[top++] = '[';
            }
        | FCOL
            {
            t[top++] = ']';
            }
        | POINT
            {
            t[top++] = '.';
            }
        | EQUAL
            {
            t[top++] = '=';
            } 
marker:     {  
            /* generic command should be here
            if any of the commands above were found it should run whatever is here*/
            }

I have formulated my answer to match the comments in the code, which are somewhat at odds with the text of your question. If you want command to match anything, not just F, PLUS, etc., then you will have to spell out all of the tokens that your lexer can generate in productions for command. This is not necessarily a good idea, for several reasons.