Question: While using functionality of authentication through firebase, emulator is showing error i.e.{ you attempted to use a firebase module that is not installed on your android project by calling firebase.app() }.Please help me to resolve this error.
I'm using Expo as command line input.

```
react-native version -0.63.6,
"@react-native-firebase/app": "^8.4.3",
"@react-native-firebase/auth": "^9.2.3"

```

![emulator](https://i.stack.imgur.com/GfOAc.png)

Answer: 
The regex to match a string which `starts with A- and ends with a digit`
should be: `^A-.*[0-9]$` or more strictly `^A-.*[[:digit:]]$`.
Then please modify your scpipt as:

```
#!/bin/bash

VAR="A-1"

if [[ $VAR =~ ^A-.*[0-9]$ ]]; then
    echo "yes"
else
    echo "no"
fi

```

Then invoke it with `bash test.sh`, not with `sh test.sh`.
`sh test.sh` does not use `bash` to run the script, it uses `sh`, which, depending on the system, may not have the same capabilities as bash.

You can use:

```
bash test.sh

```

Or:

```
chmod a+rx test.sh # one time only
./test.sh          # your script is set to use /bin/bash in the #! line.

```