Integer expression expected error in shell script

Question

I'm a newbie to shell scripts so I have a question. What Im doing wrong in this code?

#!/bin/bash
echo " Write in your age: "
read age
if [ "$age" -le "7"] -o [ "$age" -ge " 65" ]
then
echo " You can walk in for free "
elif [ "$age" -gt "7"] -a [ "$age" -lt "65"]
then
echo " You have to pay for ticket "
fi

When I'm trying to open this script it asks me for my age and then it says

./bilet.sh: line 6: [: 7]: integer expression expected
./bilet.sh: line 9: [: missing `]'

I don't have any idea what I'm doing wrong. If someone could tell me how to fix it I would be thankful, sorry for my poor English I hope you guys can understand me.

Answer 1

You can use this syntax:

#!/bin/bash

echo " Write in your age: "
read age

if [[ "$age" -le 7 || "$age" -ge 65 ]] ; then
    echo " You can walk in for free "
elif [[ "$age" -gt 7 && "$age" -lt 65 ]] ; then
    echo " You have to pay for ticket "
fi

Answer 2

If you are using -o (or -a), it needs to be inside the brackets of the test command:

if [ "$age" -le "7" -o "$age" -ge " 65" ]

However, their use is deprecated, and you should use separate test commands joined by || (or &&) instead:

if [ "$age" -le "7" ] || [ "$age" -ge " 65" ]

Make sure the closing brackets are preceded with whitespace, as they are technically arguments to [, not simply syntax.

In bash and some other shells, you can use the superior [[ expression as shown in kamituel's answer. The above will work in any POSIX-compliant shell.