Code on Evan Hoffman

Reorganizing photos in 1 line with exiftool

Fri, 02 Mar 2012 10:01:11 +0000

A few years ago I wrote a utility in Java to find all JPG files in a directory and move them into a date-based directory structure like /YYYY/MM/DD/ based on the date the photo was taken, extracted from the exif metadata in the file. Well, apparently that was a huge waste of time, as I just discovered that exiftool, an awesome perl utility I’ve used for years to edit/extract the metadata on the command line, can also do this natively. So my entire program can be replaced with this simple command:

Graphing SSH dictionary attacks with HighCharts

Fri, 18 Nov 2011 14:06:03 +0000

After my 10-year-old basement Linux server died this week from a power outage, I took the sad step of giving up on it. It’s died before and I’ve patched it back together with a new power supply here or an addon PCI SATA card there, but I finally decided to throw in the towel since I had a newer old computer that had been idle for several years. The one that died was an Athlon K7 750 MHz with 512 MB ram. The new one is an Athlon 2 GHz (3200+) with 1 gig. For my uses, specs don’t really matter that much, but it’s nice to have more power for free.

Displaying currently-playing iTunes track in the Mac menu bar

Fri, 21 Oct 2011 14:48:42 +0000

In an attempt to teach myself Objective C, and because I couldn’t find anything that did what I wanted, I wrote a little utility to display the currently-playing iTunes track in the Mac taskbar. Originally I had it display the full track name right in the taskbar but it was too much text for such a small space (especially on a 1440x900 screen), so now you click a little musical note and it shows you the info in a menu.

Benchmarking DNS servers with Java

Mon, 26 Sep 2011 12:33:28 +0000

I’m currently in the process of moving our DNS over to another provider and I was curious as to whether the old or new provider offers faster lookups. dig shows query times, but I didn’t want to just run that over and over. I decided to write something to do this, in Java since I like Java. I found this post, which has the meat of the work done already. I also read some of Sun’s JNDI/DNS lookup info, which was pretty dense. All I want to do is specify the name server’s IP and do the lookup. I don’t even really care about the result, just how long the query takes.

Amazon SES: "illegal headers" with ses-send-email.pl (followup)

Tue, 02 Aug 2011 14:39:45 +0000

A few people have emailed me asking me to integrate the perl code snippet into I wrote to strip illegal headers when sending email via Amazon SES into something actually usable. I’ve done so! I haven’t really tested this beyond sending some test emails, but here it is. Use this at your own risk, I make no warranty, blah blah blah. This fix requires editing ses-send-email.pl, so I’d advise making a backup copy, though I imagine you can always get a fresh version from Amazon if necessary.

MongoDB logrotate script

Thu, 21 Jul 2011 10:10:26 +0000

Daily mongodb log rotation via logrotate.

Teaching myself node.js: Part 3

Thu, 23 Jun 2011 17:39:59 +0000

Notes on MongoDB’s ObjectID vs sequential identifiers.

JavaScript regex for stripping leading & trailing whitespaces

Wed, 22 Jun 2011 00:09:51 +0000

str.replace(/^(\s*)((\S+\s*?))(\s)$/,"$2");

Teaching myself node.js: Part 2

Sat, 18 Jun 2011 00:45:02 +0000

More work learning node.

Teaching myself node.js: Part 1

Tue, 14 Jun 2011 00:50:59 +0000

In which I try to learn node.js by building a Quora-like site (since it seems everyone is building a blog).

Calculating SHA-1 sums in Java

Wed, 25 May 2011 18:19:27 +0000

Java code for calculating SHA-1 sums from arbitrary InputStreams, files, or Strings and printing them as strings.

Integrating Amazon Simple Email Service with postfix for SMTP smarthost relaying.

Thu, 28 Apr 2011 12:23:47 +0000

How I configured an EC2 instance to relay mail through Amazon’s SES, and some of the bumps I encountered along the way.

Perl script to calculate DNS queries per second in BIND (named)

Tue, 07 Dec 2010 18:53:43 +0000

I’m pricing out DNS providers and was asked what our current queries-per-second currently are. Sadly I had no idea. After lots of Googling I decided there was really no good way to get this information so I decided to parse the logfile myself. First, I turned on logging with timestamp in named.conf:

logging
{
...
 # Query logging 2010-12-07
 channel query-log {
 file "data/queries.log" versions 3 size 10m;
 print-time yes;
 };
 category queries { query-log; };
};
options
{
...
 # Query logging 2010-12-07
 querylog yes;

};

ldapsearch example on Active Directory

Thu, 26 Aug 2010 10:40:18 +0000

Just putting this here for safekeeping since I couldn’t remember the exact syntax.

[evan@ehoffman 10:35:50 ~]$ ldapsearch -x -LLL -D "ldapuser@example.com" -w password -b "OU=Users,DC=example,DC=com" -s sub -H ldaps://activedirectory.example.com "(sn=hoffman)" cn mail displayName samaccountname
dn: CN=Evan Hoffman,OU=Tech,OU=Users,DC=example,DC=com
cn: Evan Hoffman
displayName: Evan D. Hoffman
sAMAccountName: ehoffman
mail: Evan.Hoffman@example.com

Explanation: Connect to activedirectory.example.com using ldaps (SSL) with simple authentication, binding as ldapuser@example.com with password password; search for (sn=hoffman) within the OU=Users,DC=example,DC=com search base (branch), and search the subtree. Return the cn, displayName, and samaccountname fields.

Java Code: searching a Binary Search Tree for the largest value strictly less than X

Sun, 09 May 2010 13:43:17 +0000

Java code for creating and searching a Binary Search Tree of any element implementing the Comparable interface.

Code to flatten a list in Java, with and without recursion

Sat, 17 Apr 2010 23:42:16 +0000

Recently had someone ask me to solve this problem: assume you have a list of objects, some of which may be lists of arbitrary depths. Write a function to return the list “flattened,” so sublists are all in the “main” list. I solved it recursively pretty easily, but it took some thought to do it without recursion. My solutions are below.

package com.evanhoffman.listflattener;

import java.util.LinkedList; import java.util.List; import java.util.ListIterator;

import org.apache.log4j.BasicConfigurator; import org.apache.log4j.Logger;

Java compound interest calculator

Thu, 10 Jan 2008 00:00:08 +0000

I wrote a thing to calculate compound interest and print out how much you’ve accrued after each period. It’s pretty basic but I was bored and didn’t want to do it via calculator. The code is in InterestCalculator.java, sample output is below:

Initial principal: 5000.00
Interest rate: 0.05 (4.93%)
# of ann. periods: 4
Total years: 5
Annual Addition: 500.0
Starting year 1 with $5000.00
Year 1, period 1, accrued $61.62, value is now: $5061.62
Year 1, period 2, accrued $62.38, value is now: $5124.01
Year 1, period 3, accrued $63.15, value is now: $5187.16
Year 1, period 4, accrued $63.93, value is now: $5251.09
Added $500.00 for the end of year 1, total is now: 5751.09
Starting year 2 with $5751.09
Year 2, period 1, accrued $70.88, value is now: $5821.98
Year 2, period 2, accrued $71.76, value is now: $5893.73
Year 2, period 3, accrued $72.64, value is now: $5966.37
Year 2, period 4, accrued $73.54, value is now: $6039.91
Added $500.00 for the end of year 2, total is now: 6539.91
Starting year 3 with $6539.91
Year 3, period 1, accrued $80.60, value is now: $6620.51
Year 3, period 2, accrued $81.60, value is now: $6702.11
Year 3, period 3, accrued $82.60, value is now: $6784.71
Year 3, period 4, accrued $83.62, value is now: $6868.34
Added $500.00 for the end of year 3, total is now: 7368.34
Starting year 4 with $7368.34
Year 4, period 1, accrued $90.81, value is now: $7459.15
Year 4, period 2, accrued $91.93, value is now: $7551.08
Year 4, period 3, accrued $93.07, value is now: $7644.15
Year 4, period 4, accrued $94.21, value is now: $7738.37
Added $500.00 for the end of year 4, total is now: 8238.37
Starting year 5 with $8238.37
Year 5, period 1, accrued $101.54, value is now: $8339.90
Year 5, period 2, accrued $102.79, value is now: $8442.69
Year 5, period 3, accrued $104.06, value is now: $8546.75
Year 5, period 4, accrued $105.34, value is now: $8652.09
Added $500.00 for the end of year 5, total is now: 9152.09
Final value: $9152.09

Java utility to reorganize photos by date taken (via EXIF metadata)

Wed, 28 Mar 2007 00:00:37 +0000

I wrote a little utility to reorganize my digital camera pics based on the EXIF date-taken data stored in the pic. It’s pretty simple, I hacked it together in about an hour, but I thought it might be worth sharing for anyone else looking to do something similar. My camera organizes stuff as it sees fit sometimes, I am particular about my directory structure. This is probably a job best left to perl, but I don’t feel like getting Perl running on my Windows box where all the pics are. Now I can finally burn all my images to DVD.