bash - Binary Sludge

bash

A collection of 12 posts

Talk: Assertion - or it Didn't Happen (in Cloud Networks) - CfgMgmtCamp, Feburary 2018

Thanks to CfgMgmtCamp for having me, here are the slides for Assertion - or it Didn't Happen (in Cloud Networks). netassert is a tool to invade network namespaces and test Kubernetes Network Policy - all the code for the demos and configuration is at https://github.com/controlplaneio/netassert Talk

Mastering the Shell (and many other applications) aka Readline Shortcuts

These should all be committed to muscle memory by now, but some continue to elude me: Emacs keys Action Scope Direction/Place Moving around Ctrl-b Move the cursor one character ⇦ to the left Ctrl-f Move the cursor one character ⇨ to the right Alt-b Move the cursor one

BASH Subshell Gotchas

It's always helpful to remember that not all BASH operations are created equal. In dicing with configuring an environment I failed to recall the first rule of BASH scripting: Know Your Subshells! In this exampe n is always 0. This is because the increment operation is in a

Migrate Karma Config to 0.10

Karma has changed its config file format from plain ol' Javascript to RequireJS module.exports format. I've written a quick script to migrate a config file from one format to the other. It's been tested on Linux and OSX. Usage: migrateKarmaConfig.sh [options] path-to-

The Definitive Guide to Bash Command Line History

I found a comment in one of my environment files reminding me how to prevent commands prefixed with a space from being logged in BASH's history file: export HISTIGNORE="&:[ ]*:exit" Fortunately the comment pointed me back to the original source of the trick: The Definitive

Recovering from a forced push to a tracked repository

If a remote repository has been force updated (git push -f), the local repository's history must be rewritten to account for it (unless the master is incorrect, in which case a forced update may be the only corrective measure). A reset with the --hard flag will reset the

Easy CLI JSON Formatting

Command line JSON interpretation can be confusing. Python's json library (2.6+) provides a simple prettifier: $ echo '{"json":"obj"}' | python -mjson.tool { "json": "obj" } Or facetiously (from the obligatory Internet Chuck Norris Database): $ curl -s "http://api.

The magic of Pipe Viewer (pv)

pv is a handy pipe viewing tool that gives feedback on the progress of long-running shell operations. From the website: pv - Pipe Viewer - is a terminal-based tool for monitoring the progress of data through a pipeline. It can be inserted into any normal pipeline between two processes to

BASH variable scope

As outrageously counter-intuitive as it may first appear, it is still possible to be hit by a scope bug in BASH when commands are executed in a subshell. I was running through The Advanced Bash-Scripting Guide's "Complex Functions and Function Complexities" (a long but

Fix postfix "fatal: open database /etc/aliases.db: No such file or directory" error

As there was no email coming from a VM, I checked /var/log/maillog: Jun 25 10:59:13 localhost postfix/local[20793]: fatal: open database /etc/aliases.db: No such file or directory As the missing file is some form of (Berkley?) DB, a simple touch doesn't

parallel.sh - simple BASH parallelism

I've written a simple bit of BASH for running jobs in parallel. It's not a replacement for GNU Parallel (which has far more features!), but works well enough for simple jobs or butchering into another script. Setup Set defaults, parse command line arguments and show usage.

BASH script to remove superfluous Apache/httpd modules

httpd comes with a lot of modules enabled by default. Run this simple BASH script to remove them all, re-instate those required for a default install (configtest will reveal the errors without loading the broken config) and salt to taste: CONFIG=/etc/httpd/conf/httpd.conf sed 's/