hunspell: add word to dictionary from command line

From [hunspell man page](http://www.manpagez.com/man/1/hunspell/) : ... When in the -a mode, hunspell will also accept lines of single words prefixed with any of '*', '&', '@', '+', '-', '~', '#', '!', '%', '`', or '^'. A line starting with '*' tells hunspell to insert the word into the user's dictionary (similar to the I command). ... I tried something like: echo "* my_word" | hunspell -a but the word is not in my dictionary as parsing sample file again shows it as misspelled word How does this work, how can I add custom word? Or with Aspell, or any "common" program that writes to compatible dictionaries read by Hunspell/Aspell?