How can I check the length of an argument in bash?

问题:

Let's say I want to check if the first argument is 2 characters long. I tried

if [ ${#$1} -e 2]

but it doesn't work.

回答1:

• Don't use $ in the parameter expansion
• Use -eq for numerical comparison
• Add a space before the ]:

All in all:

if [ ${#1} -eq 2 ]
then
  echo "It's two characters long"
fi