Post thumbnail of Use Bash to do Math
7 January 2011
Continue reading Use Bash to do Math

Use Bash to do Math

You don’t need calculators or other languages and compilers to do math. You can do a lot in bash (GNU Bourne-Again SHell), and it’s really easy!

Post thumbnail of How to push pop shift and unshift arrays in bash
18 November 2010
Continue reading How to push pop shift and unshift arrays in bash

How to push pop shift and unshift arrays in bash

Since you can’t really pass pointers or references to arrays and you can’t return anything other than integers, here’s how to implement push, pop, shift, and unshift in a bash shell script. I don’t know if this already exists in bash, but I couldn’t find it and I needed a data structure in a hurry.

Post thumbnail of Case insensitive regex in bash
8 November 2010
Continue reading Case insensitive regex in bash

Case insensitive regex in bash

Shopt toggles the values of variables controlling optional shell behavior. If you want to match a regular expression while ignoring the case, the easiest method is to use shopt. You can use shopt set, unset, and print out settable options such as the ability to expand aliases and debugging options.

Post thumbnail of Two ways to change case lowercase to uppercase using sed
22 June 2010
Continue reading Two ways to change case lowercase to uppercase using sed

Two ways to change case lowercase to uppercase using sed

Change lowercase to uppercase or vice versa using sed the brute force easy way and the smart way. One use of this would be finding the hardware address of an interface and converting it to all uppercase.

Post thumbnail of Bash One-liner to get IP address for each network interface
15 June 2010
Continue reading Bash One-liner to get IP address for each network interface

Bash One-liner to get IP address for each network interface

This one should be pretty bulletproof. Use a single sed command to dump the list of all ip addresses from interfaces showing in ifconfig.

Post thumbnail of Use awk to figure out your ip address from ifconfig for a bash script
3 June 2010
Continue reading Use awk to figure out your ip address from ifconfig for a bash script

Use awk to figure out your ip address from ifconfig for a bash script

99% of the time you can just use the local address to talk to yourself. This is just an example to show you how wrangle the ip address using awk. Rewrite the hosts file so the host itself can use it’s external address by name. Write out the basic stuff in hosts that doesn’t change then write out the current IP address.

Post thumbnail of Longest dumbest bash command ever
7 May 2010
Continue reading Longest dumbest bash command ever

Longest dumbest bash command ever

What would I do without the Linux shell? The sheer number of mouse clicks required to do this in Windows would result in instant and painful arthritis. For each Makefile in any child directory below pwd, It’s looking for a broken include string where the include was specified after the library and if it finds this case, it rewrites that part so it’s include/library. It’s basically the same thing done over and over for each include that might exist in any Makefile.

Post thumbnail of Use multiple processors in bash by running commands in parallel
15 January 2010
Continue reading Use multiple processors in bash by running commands in parallel

Use multiple processors in bash by running commands in parallel

Here’s a short bash script to parallelize your jobs. There are utilities already written for just this type of thing, but forget xargs. Check out xjobs instead.

Post thumbnail of Build script to utilize Makefiles to build multiple applications
29 December 2009
Continue reading Build script to utilize Makefiles to build multiple applications

Build script to utilize Makefiles to build multiple applications

You have a bunch of related applications, each has their own Makefile that knows only about their own application, but you have dependencies where one app needs to be built before another. Here’s a skeleton bash script for building any one thing or everything.

#!/bin/bash

function build {
echo "*** …

Post thumbnail of Running bash shell scripts in debug mode to trace execution
26 August 2009
Continue reading Running bash shell scripts in debug mode to trace execution

Running bash shell scripts in debug mode to trace execution

This is so handy, I can’t believe i’ve never used or even heard of this until today! You can easily run your bash shell scripts in debug mode to watch what they’re doing behind the scenes in real time. You get to see the levels of nesting when you’re inside loops and variables get replaced with their actual contents at the time of execution.
This might come in handy if you have multiple levels of nesting in ‘for’ and ‘while’ loops or a few if/then/else statements and you want to see just what is getting passed in the comparisons.

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