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 :)