S3 Upload via CURL fails when triggered via cronjob - bash

Question

I'm using a script dump-to-s3.sh to put database dumps in a S3 bucket.
When triggered manually it works perfectly but when I trigger it via this cron (as root crontab) it fails with the following error message:
crontab
31 12 * * * /home/dokku/.mongodb/dump-to-s3.sh
error from CURL
<?xml version="1.0" encoding="UTF-8"?>
<Error><Code>SignatureDoesNotMatch</Code>
<Message>The request signature we calculated does not match the signature you provided.
Check your key and signing method.</Message>...
dump-to-s3.sh
PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
#cd to dump-folder
cd /dump/folder
file="mydump.tar.gz"
bucket="mybucket"
resource="/${bucket}/dumps/${file}"
contentType="application/x-compressed-tar"
dateValue=`date -R`
stringToSign="PUT\n\n${contentType}\n${dateValue}\n${resource}"
s3Key="xxxxxxxxxxxxxxxx"
s3Secret="xxxxxxxxxxxxxxxx"
signature=`echo -en ${stringToSign} | openssl sha1 -hmac ${s3Secret} -binary | base64`
curl -X PUT -T "${file}" \
-H "Host: ${bucket}.s3.amazonaws.com" \
-H "Date: ${dateValue}" \
-H "Content-Type: ${contentType}" \
-H "Authorization: AWS ${s3Key}:${signature}" \
https://${bucket}.s3.amazonaws.com/dumps/${file}

Answer 1

I think you might need to run bash manually, e.g.
/bin/bash /home/dokku/.mongodb/dump-to-s3.sh
The -en options for echo don't work in the regular shell; it might just be a bash extension.
In sh:
$ sh
sh-3.2$ echo -en foo
-en foo
sh-3.2$
In bash:
$ bash
bash-3.2$ echo -en foo
foobash-3.2$