A Little Shell Will Fix It

Last night I went to Lights For The Wild at Taronga Zoo. As usual, I took a lot of photos with my DSLR camera, over 200, though a lot of that number are quite similar as I often take two or three to increase the chances of getting the right shot, sometimes I vary the speed so that one is better exposed.

The camera saves both a RAW file​ and a JPEG so I end up with over 400 images. Looking through them in QuickLook in the Finder can be painful as the RAW images take quite a while to load, then you get the problem that when you have decided which of the three shots you want to keep you also have to delete the matching JPEG or RAW file.

The easiest solution to both of these is to only go through the JPEG files and then delete the matching NEF file (which is what the Mac calls the RAW file).

So I open the folder and sort by ‘Kind’ which puts the JPEGs at the top. I then open the first in QuickLook by hitting space and using the up and down arrow keys to move through the list commanddelete deletes a file and displays the next. Easy.

Now I have 80 JPEG files from the original 240. How to get rid of the NEF files that match the JPEG files I have deleted? A little bash programming to the rescue.

for i in *.NEF ; do
  if [ ! -e `basename $i NEF`JPG ]; then 
    rm $i; 

The secret to this is the basename utility. It’s a neat little tool. Pass it a full file path such as /Users/tonyw/Documents/UselessRamblings.txt and it will return just
the file name without the path, UselessRamblings.txt. It has a matching tool, dirname which returns just the path portion. As you can see from my code basename has another trick, it will happily strip the suffix from the filename if you tell it what to strip.


More Tools For Building Tools

I’m working on more bash completions. This time for some of the command line tools Apple provides for sysadmins.

I decided there had to be a way to get a list of the options from the man page for a tool. After all they are all in there.

So I built a command line piece by piece. As an example let’s get a list of the options (with some caveats) for the tool pkgbuild. We start with man pkgbuild | col -b , the col -b step takes out the special characters man uses to show bold on screen. Now find all lines containing -- with grep, I liked grep -e '--'. If you have a look at the output of that we are getting close.

Next I decided to use sed to do a find and replace for the option itself. After some playing around I ended up with sed -e 's#.*\(--[a-zA-Z-]*\).*$#\1#' An important note for young players, it did take some time and a few tries to get that substitution just right. Don’t be afraid and remember Google (and Stack Exchange) are your friends.

First, I should point out an old Unix hand’s trick. Most of the time you see sed substitution commands using / as the separator but sed can use anything but \ or newline – it uses the first character it sees after the ‘s’. I usually use # as it makes the \ used for special characters easier to spot and the string easier to read.

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Now We Have bash Completion For Munki

I’m on a roll. I’ve written the bash completions for Munki.

(tl;dr The completions are on Github )

It’s getting easier to write them. There was one little trick I used that I didn’t
mention in my last post that I thought I’d share. How to use find and replace with
regular expressions to generate some of your code.

For this I use Find... in BBEdit. I started with a list of the commands, one on each
line. Continue reading

bash completion for autopkg

Over the weekend I was feeling a little bored so I decided to try my hand at writing a shell script to add custom completion for autopkg to bash.

(tl;dr – the script is on GitHub.)

I found an example for the zsh shell which lacked a couple of features and I spent some time examining the script for brew so I wasn’t totally in the dark.

There are a number of tutorials available for writing them but none are particularly detailed so that wasn’t much help.

Writing Shell Scripts

The first thing I should say is that I find writing shell scripts totally different to writing for any other language. I probably write shell scripts incredibly old school, shell and C were the two languages I was paid to write way back in the 1980’s. It feels like coming home.

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Containers Rock! Why I’m A Docker Fan

Docker for the Macintosh has recently emerged from beta and I’m ecstatic.

Docker implements a way of walling off a piece of software from the underlying operating system using a tech they call “containers”.

This is an absolute godsend for deploying services. One of the problems in system administration is the cost and complexity of spinning up a new service and then removing it from a computer once it is no longer required.

Software when it is installed and run can spray pieces of itself all over the computer’s file system and getting it out again is difficult.

Previously we have used virtual machines to isolate this problem. That has it’s own costs, a virtual machine means you are running (at least) two complete operating systems on the hardware. It also has a cost in memory and hard disk space.

Containers lower the cost considerably. They have all the advantages of virtual machines but share the operating system kernel with each other and the underlying OS. This makes them smaller and consuming considerably less resources than virtual machines. This also makes them quicker to download and deploy.

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BBEdit Really Doesn’t Suck

Recently, with version 11, BBEdit introduced a demo mode so I thought to take another look at the big brother of TextWrangler. I have to say BareBones Software’s tag line for BBEdit is true “BBEdit – It doesn’t suck!”.

There are two tasks that I use an editor for, writing Python and writing Markdown so those are the two that I looked at.

There are a number of things you can do to improve BBEdit as a Python IDE. The first is to install Dash. This is a brilliant tool for searching documentation sets and can be easily searched from BBEdit. Just select a library call and choose “Find In Reference…” under the Search menu and BBEdit will pass the search to Dash. Dash will search across all your documentation sets but it is easy to set the sort order so the Python entries are close to the top and in the Dash results window there is a little Python icon next to the Python results.

The other neat item under the Search menu is “Find Definition”, this will find where in your file a function is defined – useful if you have a long source file.

But how does that work if our project is in multiple source files? Well, Unix has long known of that problem and had a solution. It’s a tags file, first used in vi. This is a file that lists all the function definitions and variables used in all the files in a directory tree. Not only can BBEdit use a tags file but it can (using the open source utility cats) generate them. At the top of your project directory tree, on the command line bbedit --maketags will generate a tags file and now “Find Definition” will work across all the Python files in the tree.

BBEdit can also run a syntax check across your source. You will find “Check Syntax under the ”#!“ menu which also allows you to run your Python code. The final entry in this menu ”Show Module Documentation” displays a new text window with the output from running pydoc across your file. I love this, it encourages me to properly document my code as I write with pydoc strings for each function. The output is extremely useful as a memory aide for large programs and modules.

Next up is running a lint across our Python source. BBEdit comes with another command line tool, bbresults which turns formatted error output from Unix command-line tools into a BBEdit results windows. This is an exceptionally neat trick. At the command line flake8 example.py | bbresults will give you a window in BBEdit with each of the errors and warnings listed and a click on one will take you to the exact spot in your source. If you don’t have flake8 installed then you can install it with conda or pip.

By the way, this works because the bbedit and bbresults command line tools understand the +n argument syntax for going to line n in a file. Sublime Text and other editors on the Mac could learn this.

A final tip for programmers, BBEdit recommends setting the $EDITOR shell variable to bbedit -w where the -w flag has the bbedit command line tool wait till you close the window before exiting. If you add the --resume flag as well then when you close the window in BBEdit it will return the Terminal to the front. Exceptionally handy.


One complaint I would make, and I make it about a number of editors, is that the Markdown syntax highlighting is on the stupid side. This is generally due to the flaws in using nothing but regular expressions to do the highlighting. The most obvious flaw is that underlines in such things as a URL will trigger highlighting for italics.

If you want you can “lint” your prose using proselint and bbresults. Personally I find proselint rarely throws up something I actually want to change but your mileage might vary, it’s a good tool for looking at prose text.

BBEdit has no special facilities for writing Markdown such as inserting the codes for text styles or formatting but it does have the ability to use “Clippings”, a short piece of text, and clippings can be kept in sets and a clipping can have a keyboard shortcut. I don’t use it, I have a few Keyboard Maestro macros for such things as web links and otherwise just type the few extra keystrokes.

BBEdit also has “Text Filters”, which allow you to run the current selection through a script. For Markdown I have one that turns tab separated text into a Markdown table, incredibly useful for tables copied from a spreadsheet. Not sure where I got it but I suspect it was from Brett Terpstra’s blog.

BBEdit is a good editor, well worth the $50 purchase price and has a number of advantages over it’s free little brother TextWrangler. As both a general purpose editor and an editor for programming I’d have to say that it is the best editor available on the Mac at the moment though Sublime Text comes close.

Jupyter Releasing Some Nice Software

The Jupyter group have released an alpha version of a new Notebook environment called JupyterLab

JupyterLab is browser based, just like the old notebook system but adds a multiple pane environment. I’m not going to go into the details of the collaboration between the large number of organisations that have gone in to the development, go read the blog post announcing JupyterLab. Suffice to say that I’m glad such a high powered group are working on my favourite Python environment.

I installed the alpha (it’s quickly done with pip) and had a look. It’s an exciting looking development and will make a brilliant Python development environment.

At the moment it seems to be suffering from minor speed problems and minor layout problems in Safari (they are minor, don’t appear in Google Chrome and Safari is not currently listed as a supported browser so I’m not going to complain too loud.)

The built in editor can syntax colour Python. It even has colour themes for those, like me, who like a particular look in their editor. At the moment it is indenting only two characters with a tab (PEP 8 says it should be 4) and if you hit return with the cursor in column 1 then you get a first level indent on the next line.

These are the sort of problems you an expect in alpha software. I think I might install the current development version from Github and check there before filing a couple of bug reports. I’m a bit idiosyncratic, nothing I like more than spending an hour or two getting a bug down to it’s essentials and filing a report.

IPython 5

They have also released a new version of IPython they are calling IPython 5.0 LTS. It has some nice new features including syntax highlighting as you type and much better multi-line support. This is due to shifting from various command line interfaces to the purely Python readline replacement prompt_toolkit.

I think the move to prompt_toolkit is going to show major dividends as the library (currently at version 1.0.3) adds yet more functionality and that functionality moves into IPython. Jonathon Slenders, the author of the library, is also developing clones of Vim and tmux in pure Python using it and intends to fold features from those projects back in to prompt_toolkit.

They are designating this as “Long Term Support” as it will be the last IPython to run under Python 2. IPython 6 will require Python 3. Not is all lost though, they say they will continue to support Python 2 kernels with Jupyter Notebooks (and we assume the new Jupyter Lab). As they say in their announcement “For the 5.x series releases we are making an exception to that rule: until the end of 2017 the core team will do its best to provide fixes for critical bugs in the 5.x release series. Beyond that, we will deprioritise this work, but we will continue to accept pull requests from the community to fix bugs through 2018 and 2019, and make releases when necessary.” So it will be a while before us OS X users are forced to run Python 3 for IPython and break PyObjC and it’s brethren which are written in 2.7 (we can also hope that well before the 20202 deadline Apple moves to Python 3 and does the port of PyObjC.)

Easy Python Development

Taken together these two new releases improve Python development enormously for me. I have always been a fan of iterative development of my code in IPython and this just makes the explore and iterate method easier and easier.