Unable to pass ‘#’ character as a command-line argument

# begins a comment in Unix shells, much like // in C.

This means that when the shell passes the arguments to the progam, it ignores everything following the #. Escaping it with a backslash or quotes will mean it is treated like the other parameters and the program should work as expected.

2 4 \# 5 6

or

2 4 '#' 5 6

or

2 4 "#" 5 6

Note that the # is a comment character only at the start of a word, so this should also work:

2 4#5 6