* on the linux command line

Question

I am making a little calculator in C, and i want to pass simple arithmetic formulae to my program. But it really does not like me passing character '*' to my program. Why not? And how can I work around this without changing the asterix to something else? Thanks

Answer 1

The character * is the shell's trigger for expanding matching filenames.

There are several ways to deal with it:

• Escape it when typing mycalc 5 \* 3
• Place the whole expression in quotes and make sure the calculator's parser works that way: myprog "5 * 3"
• Don't use the command line: use your own input instead.

Answer 2

* gets expanded to match all files in the current directory (this is called "globbing"). You need to quote or escape the *, or use a different symbol.