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In the first case, you're comparing a std_logic_vector to an array of std_logic_vector. Doesn't work.
In the 2nd case, you're comparing a std_logic to a std_logic_vector. Doesn't work either.
I assume the problem is that the type of com_str is wrong. I guess it should really be this:
signal command: std_logic_vector(7 downto 0);
That would, from the context, make more sense to me.
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'command' is not a char - it's array of chars. this way - command: std_logic_vector(7 downto 0); - it holds only one char, and I need to get array of chars from terminal.