Shell on galvanist

Manpages in the GUI on OS X

Wed, 20 Nov 2013 01:17:55 +0000

Here’s a shell function to add to your profile that makes it easy to view man pages in OS X’s Preview.app:

pman() { man -t "$*" | open -f -a "/Applications/Preview.app"; }

OS X Quick Look Preview on the Command-line

Mon, 18 Nov 2013 20:56:41 +0000

The qlmanage command has a -p argument which lets you create Quick Look previews on the command line. So something like this can be nice to have in your shell profile: alias ql='qlmanage -p'.

I decided I needed something a little more featurey than an alias (because qlmanage -p README is useless). So, I made a quick python implementation of ql which has special treatment for README, LICENSE, Makefile and probably eventually other extension-less file names.

Revisiting Shell Concurrency (this time in ZSH)

Fri, 15 Nov 2013 23:08:00 +0000

I’ve been thinking about concurrency in the command shell again. This was prompted by my ongoing transition from Bash to ZSH. I’ve decided to re-implement my conc and xconc functions in a slightly different way.

Intro

Lets say you have 50 data files to compress. Here’s one way:

% xz *.dat
<< completed in 2 minutes, 4 seconds >>          
%

That’s not bad, but it doesn’t really take advantage of all those fancy cores we have in our computers these days. Let’s run multiple xz jobs as-parallel-as-possible, so that each file gets its own xz process.

Sort du intelligently

Tue, 22 Oct 2013 17:14:00 +0000

The du command is a nice tool for telling you the disk usage of your files:

$ du *
[...]
1928	system.log
136	system.log.0.bz2
112	system.log.1.bz2
0	uucp
552	vnetlib
[...]

I find that adding the -h flag (which produces more human-readable output) is often very helpful for me:

$ du -h *
[...]
964K	system.log
 68K	system.log.0.bz2
 56K	system.log.1.bz2
  0B	uucp
276K	vnetlib
[...]

Now if I could just sort that…

collect - a shell function

Fri, 24 May 2013 22:41:00 +0000

In OS X’s Finder, if you select some things then right-click you have an option called “New Folder with Selection”. ilikeitverymuch. So a while back, I though it would be alsonice to have something analogous in the command shell. I’ve been using just such a command for about six months now and let me assure you that it is very alsonice.

What does it do, under the hood?

Managed concurrency in the bash shell

Thu, 23 May 2013 07:14:00 +0000

Concurrency is all the rage these days. I started to wonder about using it in my command shell (which is regrettably still bash) because so much of the infrastructure for job control is already in place. I’ve been using xargs -P for a while, but I wondered about doing it all in the shell.

“conc”

I came up with a super-simple function to do some experiments:

export CONC_MAX=2
    
conc() {
	local procs=(`jobs -p`)
	local proc_count=${#procs[*]}
    
	# Block until there is an open slot
	if ((proc_count >= CONC_MAX)); then
		wait
	fi
    
	# Start our task
	(eval "$@") &
}
export -f conc

To use it, just throw the word ‘conc’ in front of your commands. It will only use up to CONC_MAX processes. I matched that to the number of cores I have. It is especially useful in loops. For example, while this does some things: