参考

download-db-log-file-portion — AWS CLI 1.14.46 Command Reference

前提

Amazon Linux 2

説明にはこう書かれてた

In order to download the entire file, you need --starting-token 0 parameter:

aws rds download-db-log-file-portion --db-instance-identifier myinstance
--log-file-name log.txt --starting-token 0 --output text > full.txt

スクリプト

download_rds_logs.sh

# !/bin/bash

set -u
: $1

DB_INSTANCE_IDENTIFIER=$1
OUTPUT="."

logs_json=`aws rds describe-db-log-files --db-instance-identifier ${DB_INSTANCE_IDENTIFIER} | jq ".DescribeDBLogFiles"`

len=$(echo $logs_json | jq length)
for i in $( seq 0 $(($len - 1)) )
do
        row=$(echo $logs_json | jq .[$i])
        logfilename=`echo $row | jq -r ".LogFileName"`
        size=`echo $row | jq -r ".Size"`
        if [ ${size} -gt 1000000 ]; then
                echo ""
                echo "WARN: ${logfilename} is over 1M ${size}. Please check this logfile is copmletion."
                echo ""
        else
                echo ${logfilename}
        fi
        
        # 保存用のファイル名用意
        savefile=`echo ${logfilename}| sed -e "s/\//-/g"`

        aws rds download-db-log-file-portion --db-instance-identifier ${DB_INSTANCE_IDENTIFIER} \
        --log-file-name ${logfilename} --starting-token 0 --output text \
        > ${OUTPUT}/${savefile}
done