Options to call s3 objects inside shell script from lambda?

Question

I have quite a lot of shell scripts running in linux server. Planning to migrate to cloud. Some functionalities of the script include,

• Moving list of files from one folder to another/to different server
• Business logic included to process the files
• Encryption/Decryption of files with ssh keys

Am trying to run the bash script on lambda . But When I try to call s3 bucket using AWS CLI command inside my bash script. Lambda Fails with run time error.

function handler () {
    be_bucketname=$1

    # Check whether the bucket already exists. 
    # We suppress all output - we're interested only in the return code.
    aws s3api head-bucket \
        --bucket s3://mybucket \
        >/dev/null 2>&1

    if [[ ${?} -eq 0 ]]; then
        return 0        # 0 in Bash script means true.
    else
        return 1        # 1 in Bash script means false.
    fi
    RESPONSE="{\"statusCode\": 200, \"body\": \"be_bucketname\"}"
    echo $RESPONSE
}

So how can I read s3 objects using shell scripts from Lambda. If I use Python to call shell script will aws cli works.