aspell cannot open files

Good Afternoon.

I've just started using Ubuntu, so i don't know many basic thinks, and my
question will probably be stupid. But I am trying to make aspell sellcheck
my .tex file, using the command

aspell -c -t myfile.tex

and  I keep getting the message

cannot open the file myfile.tex for reading

So, how can i make it work properly? I could not find the answers anywhere
on the web. Thanks for much for your help.

Best regards,

Gustavo Costa