Mini Magick

I just discovered MiniMagick. It is exactly what I was looking for in a ruby-language wrapper for ImageMagick.

I’ve been using ImageMagick forever. Like, more than 20 years foreer. Maybe 30 years;  I don’t know when it was first developed, or how old it was when I discovered it.

Some of the time, I use ImageMagick from the command line: just convert a file or montage a couple of them, or whatever. But sometimes, I do the same three things to an image and expect to do it over and over again for multiple images, I’ll write a shell script.

Writing shell scripts is hard. (Like, do you use trap? Of course you don’t.)

Writing Ruby is easy. But the only Ruby wrapper for ImageMagick I knew about was RMagick, which is big and complex and the first couple of times I tried to use it I had build problems (this was back before gems and github).

So there I was. Use bash and keep it simple, or use ruby with some crazy backtick `convert foo.png foo.jpg` shell escape there instead of doing it right.

But MiniMagick is just a well-designed wrapper around those backticks. Kudos!

Bash Initialization

Every time I monkey with my .profile or .bashrc file I regret it.(.profile is what graybeards like me use instead of using .bash_profile like all the young people who won’t stay off my lawn.)

If you’re like me, you get those confused all the time, so let’s go to the bash(1) man page. (Amazingly, it is a man page and not an info node. Ahem.) Here’s the salient bit of that 37,000 word tome:

When bash is invoked as an interactive login shell, or as a non-interactive shell with the –login option, it first reads and executes commands from the file /etc/profile, if that file exists. After reading that file, it looks for ~/.bash_profile, ~/.bash_login, and ~/.profile, in that order, and reads and executes commands from the first one that exists and is readable. The –noprofile option may be used when the shell is started to inhibit this behavior.

When a login shell exits, bash reads and executes commands from the files ~/.bash_logout and /etc/bash.bash_logout, if the files exists.

When an interactive shell that is not a login shell is started, bash reads and executes commands from ~/.bashrc, if that file exists. This may be inhibited by using the –norc option. The –rcfile file option will force bash to read and execute commands from file instead of ~/.bashrc.

When bash is started non-interactively, to run a shell script, for example, it looks for the variable BASH_ENV in the environment, expands its value if it appears there, and uses the expanded value as the name of a file to read and execute. Bash behaves as if the following command were executed:

if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi

but the value of the PATH variable is not used to search for the file name.

Got all that? The key is that your .profile is read first for login shells and .bashrc for non-login shells. There’s no reason why you should ever worry about what order they get invoked in, because there’s no reason to invoke them both at all. Except if you want to observe the DRY principle. In which case they should both invoke a separate startup file of your own design.