Algorithms, Design, Code and more: April 2013

Saturday, April 20, 2013

Linux/Unix Shell Function For Date Addition and Subtraction

Here is a small shell script to do date addition and subtraction. This works on the bash shell with GNU Date.

#!/bin/bash

function getPreviousDateTime(){
d1=`date -d "$1" +'%Y-%m-%d %H:%M:%S'`;
secs1=`date -d"$d1" +%s`;
secs2=`expr $secs1 - $2`;

# change to %H:%M:%S if you want the nos. left padded
result=`date -d@"$secs2" +'%Y-%m-%d %-H:%-M:%-S'`;
# return formatted string
echo $result;
}

function getNextDateTime(){
d1=`date -d "$1" +'%Y-%m-%d %H:%M:%S'`;
secs1=`date -d"$d1" +%s`;
secs2=`expr $secs1 + $2`;
result=`date -d@"$secs2" +'%Y-%m-%d %H:%M:%S'`;
# return formatted string
echo $result;
}

# Tests

echo `getPreviousDateTime "2012-04-29 18:00:31" 30`
echo `getPreviousDateTime "2012-04-29 00:00:00" 60`
echo `getPreviousDateTime "2012-04-29 02:00:00" 60`

echo `getNextDateTime "2012-04-29 19:00:00" 60`;
echo `getNextDateTime "2012-04-30 23:59:00" 60`;
echo `getNextDateTime "2012-02-28 23:59:00" 60`;
echo `getNextDateTime "2012-02-28 2:59:00" 60`;

Wednesday, April 17, 2013

Upload to Amazon S3 Bucket via Signed Url with Server Side Encryption

Continuing further from my previous post on upload & download from Amazon S3 bucket via signed url's, here is how to enable Server Side Encryption (SES) with the file being uploaded to S3.

Add a x-amz-server-side-encryption request parameter with the GeneratePresignedUrlRequest before getting the signed url:

Monday, April 1, 2013

Upload and Download from Amazon AWS S3 Bucket via Signed Url

While the code snippets are using the Java AWS SDKs, principally these will work with the other SDKs as well.

1. Get hold of FederatedCredentials using your AWS credentials:

Pass in proper access Policy settings for the FederatedCredentials on the S3 Bucket and/ or Item.

E.g.

For Download you could additionally set up ResponseHeaderOverrides for withContentDisposition, ContentType, etc.

2. Get BasicSessionCredentials using the Federated Credentials

3. Generate GeneratePresignedUrlRequest

4. Finally, generate a pre-signed url via the S3Client object:

5. To test this:
- Download:
Get the url.toString() & hit it from a browser

- Upload: