Simple if/else not working

Question

i have been looking at this for an hour without figuring out what the problem is. The else statement is not working for some reason.

#!/bin/bash
if [ $#=3 ]
then
echo $*
else
echo "error" 1>&2
exit
fi

Answer 1

The problem is in the line:

if [ $#=3 ]

As you have no spaces around =, it is necessarily doing:

if [ -n $#=3 ]

test which will always be true as =3 is always there, hence the else will never be triggered.

You need to use spaces around =:

if [ $# = 3 ]

Also use double quotes on variable expansion to avoid word splitting and pathname expansion, not strictly necessary in case of $# though.