Thursday, November 30, 2017

bash startup files and aliases

Today I hosted a Beer and Tech session at Entelect on Automating Database Deployments (with Flyway).

During the session, I was using the Bash terminal to edit files or run Flyway, and interacting with git quite a bit - as we all know, using git on the command line is the best way to do so ;D

After the session, a colleague asked me how I created shortcuts for certain commands, and I explained to him how Bash supports aliases and that these can be loaded by a startup file. There are various startup files, but I tend to use ~/.bash_profile and not ~/.bashrc. Here are some of the shortcuts I currently have setup:

alias cls='clear'
alias l='ls -Al'
alias ..='cd ..'

alias gf='git fetch --prune'
alias gl='git log --name-status --abbrev-commit'
alias grh='git reset --hard'
alias gs='git status'

And so on. If you modify the file, you have to re-load these into the current session, or restart a new terminal session. To reload the file, you can just do the following:

$ . ~/.bash_profile

Hope this helped someone :)

Thursday, July 20, 2017

git - exclude files in a diff

In some scenarios you might have a build server that doesn't have access to the Internet, in which case if you're working with something like npm, you might need to commit your node_modules folder to the git repository to get stuff to work.

Of course, it might be better to setup your own artifact repository such as Nexus on an internal network for these dependencies, BUT, I didn't have that! :D The node_modules are included as part of a commit.

Having to do a code review of a pull request can be tricky because of this, due to more than 10,000 files being in the commit, of which only 40 are actual source files of interest. We're using TFS 2017 which has a nice web interface for doing this, however it only supports showing 1000 files at a time.

So back to the best way to use git: the command line :)

To exclude the node_modules from the diff was as simple as doing the below:

$ git diff master develop -- . ':!node_modules'

Of course, I used difftool because I prefer WinMerge but it works the same.

Wednesday, April 19, 2017

Finding currently executing queries and parameters

If you've worked with an Object Relational Mapper (ORM) such as Hibernate, NHibernate, Entity Framework, etc., then you'll know these sometimes convert your queries into parameterized queries that can become quite beastly.

Trying to debug it means either profiling the database to see what queries are executing, and then seeing the query and values from there, or if you can't profile it, maybe selecting from some system tables to do a similar thing.

This snippet below (thanks again StackOverflow) will give you some nice details about the queries on a database, including an XML query plan that contains the parameters that were used when generating the query plan. It can be useful in diagnosing slow queries:

select * 
from sys.dm_exec_requests r 
cross apply sys.dm_exec_query_plan(plan_handle) as qp
cross apply sys.dm_exec_sql_text(r.sql_handle) 
where r.database_id = DB_ID('<dbname>') 

Thursday, March 23, 2017

tail on Windows with PowerShell

One of the well known Unix/Linux commands is tail, which gets the tail of a file, meaning the end of a file and prints it out to the output stream.

I used to try find nice programs for this, including Baretail which has some very nice features like colouring lines in that match certain patterns etc.

But if you just want a simple, and now built into Windows solution, just use PowerShell:

Get-Content -Tail 10 filename.txt

This will show the last 10 lines of the file. You can even follow the tail, or watch it for changes, as below:

gc -Tail 10 -Wait filename.txt

Another nice thing you can do is then pipe this into Select-String to filter the output:

gc -Tail 10 -Wait filename.txt | Select-String -Pattern somepattern

Monday, March 20, 2017

diff PDF files

At a client we have a PDF template that needs to be used for registering users. When this is updated, the template is overriden. But it would be nice to be able to easily see what changed between the two.

Well, this is possible :)

You can use Imagemagick and Ghostscript to do this.

You should be able to just do the below:

magick compare old.pdf new.pdf diff.pdf

But that didn't seem to work well. What seems to work better is to rather convert the PDF to an image first, and then compare each page.

magick convert -density 300 -quality 100 old.pdf old.png
magick convert -density 300 -quality 100 new.pdf new.png

magick compare old-0.png new-0.png diff-0.png

Depending on the options you can get better or worse results. Changing the colorspace to CMYK for example could yield better results, or maybe using options to blur/sharpen/despeckle the image too. Try play around with the options to see better results.

The best results I had was actually via using Adobe Acrobat to first export the PDF to images, and then run the compare. I still need to figure out why, because unfortunately I only have the license at work, so this won't always be an option. I'll hopefully update this post in future to show my favourite variation :)

Tuesday, February 21, 2017

Modern Database Development Practices

Back in November 2012 I presented on this topic at Entelect's Dev Days.

I've also done a blog post previously on setting up Flyway.

I keep referring back to the same links and concepts and this post is here just for that, as a pointer to good resources and brief points about this topic.

I may revisit it and put down my own consolidated content, but for now this will do.

Wednesday, February 15, 2017

C# - Testing that different cultures won't affect formatting

Ever worked on a system where you write code and test it and it all works perfect, but then maybe a unit test starts failing on a build server, or maybe a report looks wrong to the consumers of the report, all because it formatted a number to "12345,67" instead of "12345.67"?

This tip will help you.

First, lets assume we have this code:

public class ReportFormatter
  public string Format(decimal value)
    return value.ToString();

And a nice little unit test for it:

public sealed class ReportFormatterTest
  public void Format()
    var sut = new ReportFormatter();
    var result = sut.Format(12345.67M);
    Assert.AreEqual("12345.67", result);

This works perfectly fine. Lets even imagine that all our machines all have the same setup, and all are set to use the same regional settings. Great, nothing should ever break.

Until maybe Microsoft releases a patch to Windows that changes our regional settings to be "correct" - in fact, South Africa should be using a comma as a separator... even though none of us use this standard :D

So then it breaks our code, and our business rules that disagree with it.

Well, the good news is we can change the regional settings of the running thread, by changing its CultureInfo details. Here is a little utility class to do so:

public class TemporaryCultureSwitch : IDisposable
  private readonly CultureInfo _originalCulture;
  private readonly CultureInfo _originalUICulture;
  public TemporaryCultureSwitch(CultureInfo cultureInfo)
    _originalCulture = Thread.CurrentThread.CurrentCulture;
    _originalUICulture = Thread.CurrentThread.CurrentUICulture;
    Thread.CurrentThread.CurrentCulture = cultureInfo;
    Thread.CurrentThread.CurrentUICulture = cultureInfo;
  public TemporaryCultureSwitch(string cultureName) : this(new CultureInfo(cultureName)) { }
  public void Dispose()
    Thread.CurrentThread.CurrentCulture = _originalCulture;
    Thread.CurrentThread.CurrentUICulture = _originalUICulture;

We can now update our test to be a bit more specific:

public void FormatShouldNotBeAffectedByCultureChanges()
  var culture = new CultureInfo("en-ZA");
  culture.NumberFormat.NumberDecimalSeparator = ",";
  using (new TemporaryCultureSwitch(culture))
    var sut = new ReportFormatter();
    var result = sut.Format(12345.67M);
    Assert.AreEqual("12345.67", result);

Now we have a test that will fail consistently! Time to fix the code. One way of doing this is realizing that there is an overload of Decimal.ToString that takes in a CultureInfo object. We actually can use the InvariantCulture as below:

public string Format(decimal value)
  return value.ToString(CultureInfo.InvariantCulture);

The test passes and we now know for sure that regional settings won't affect our code.

Wednesday, January 25, 2017

Uninstall Windows Service using PowerShell

You can get a list of services using the Get-Service cmdlet, for example, to retrieve a list of all running services you could run:

Get-Service | Where-Object { $_.Status -eq "Running" }

You could even retrieve a specific service and start/stop it:

$service = Get-Service DemoService

However, there is nothing to remove the service on this object.

We can also use GetWmiObject to do the same things:

$service = Get-WmiObject Win32_Service -Filter "name='DemoService'"

But this WMI object actually also exposes a delete functionality, which will mark the service to be deleted.

$service = Get-WmiObject Win32_Service -Filter "name='DemoService'"

If there are resources that are being held onto, it will only be deleted once they're freed up - whether it's the service that needs to gracefully shutdown still, or maybe the services manager snap-in (services.msc) has an open properties window open (I think that's happened to me before), and closing it then puts the delete through.