Get the MD5 value of an S3 file using curl - amazon-web-services

Question

In order to get a particular file from S3, I use, the script shown below:
# Get the configuration file
outputfilecfg=XXXX
amzFilecfg=XXXX
bucket=XXXX
resource="/${bucket}/${amzFilecfg}"
contentType="text/plain"
dateValue=`date -R`
stringToSigncfg="GET\n\n${contentType}\n${dateValue}\n${resource}"
s3Key=$S3_KEY
s3Secret=$S3_SECRET
signature=`echo -en ${stringToSigncfg} | openssl sha1 -hmac ${s3Secret} -binary | base64`
curl -H "Host: ${bucket}.s3.amazonaws.com" \
-H "Date: ${dateValue}" \
-H "Content-Type: ${contentType}" \
-H "Authorization: AWS ${s3Key}:${signature}" \
https://${bucket}.s3.amazonaws.com/${amzFilecfg} -o $outputfilecfg
Now I want to be able to get the value of
the object metadata as specified by the S3 docs(https://docs.aws.amazon.com/AmazonS3/latest/dev/UsingMetadata.html). I want to be able to do this exclusively through curl and not the aws-cli. Is this possible?

Answer 1

You can get just the object metadata by making a HEAD request instead of a GET request. To make a HEAD request in cURL, use the -I option.
curl -I -H "Host: ${bucket}.s3.amazonaws.com" \
-H "Date: ${dateValue}" \
-H "Content-Type: ${contentType}" \
-H "Authorization: AWS ${s3Key}:${signature}" \
https://${bucket}.s3.amazonaws.com/${amzFilecfg} -o $outputfilecfg
For more details about either of these, see
S3 documentation for the HEAD Object API
cURL manual