What command means "do nothing" in a conditional in Bash?

Question

Sometimes when making conditionals, I need the code to do nothing, e.g., here, I want Bash to do nothing when $a is greater than "10", print "1" if $a is less than "5", otherwise, print "2":

if [ "$a" -ge 10 ]
then
elif [ "$a" -le 5 ]
then
    echo "1"
else
    echo "2"
fi

This makes an error though. Is there a command which will do nothing and also not slow down my script?

Answer 1

The no-op command in shell is : (colon).

if [ "$a" -ge 10 ]
then
    :
elif [ "$a" -le 5 ]
then
    echo "1"
else
    echo "2"
fi

From the bash manual:

: (a colon)
Do nothing beyond expanding arguments and performing redirections. The return status is zero.