turn role info in env variables.

role-creds.sh

#!/usr/bin/env bash

which jq > /dev/null 
if [ $? != 0 ]; then
    echo "You need to install jq for this to work"
    exit 1
fi

which aws > /dev/null
if [ $? != 0 ]; then
    echo "You need to install awscli for any of this to work"
    exit 1
fi

usage() {
    echo "Usage: $0 -r ROLE_ARN -s SESSION_NAME"
    exit 1
}

while getopts "r:s:" o; do
    case "${o}" in
        r)
            ROLE_ARN=${OPTARG}
            ;;
        s)
            SESSION_NAME=${OPTARG}
            ;;
        *)
            usage
            ;;
    esac
done

if [ -z "$ROLE_ARN" ] || [ -z "$SESSION_NAME" ]; then
    usage
fi

unset AWS_ACCESS_KEY_ID
unset AWS_SECRET_ACCESS_KEY
unset AWS_SESSION_TOKEN

OUTFILE="$SESSION_NAME.env"
aws sts assume-role --role-arn "$ROLE_ARN" --role-session-name "$SESSION_NAME" | \
    jq -r '"export AWS_ACCESS_KEY_ID=\(.Credentials.AccessKeyId)\nexport AWS_SECRET_ACCESS_KEY=\(.Credentials.SecretAccessKey)\nexport AWS_SESSION_TOKEN=\(.Credentials.SessionToken)"' \
       | tee $OUTFILE

echo "'source $OUTFILE' to assume the role." >&2