Principal Software Engineer/Architect, motorcyclist, drummer, and artist
All things computing.
One of the key features in go is simplicity. As a result there are a number of utilities and data structures that are common in other high-level languages that do not come with the go stdlib.
One of them is a stack. Following is a very simple implementation of a stack that uses a slice to store the data.
The following is an implementation of a simple stack that takes any kind of pointer.
import "fmt"
type Stack[T any] struct If you want to execute curl commands on your local machine and connect to an HTTPS server that is only reachable from a bastion or other host through which you can only get to via SSH, the following is how you set up the SSH tunnel and execute the curl command.
The following will not work
# Create ssh tunnel
#
ssh -L localhost:8443:example.com:443 user@bastion.example.com
# Attempt to hit the endpoint otherwise accessible from bastion.example.com
# with curl -X GET The GNU diff command on most Linux and UNIX systems will diff the contents of two files. With Bash, you can, using process substitution, take the output of any arbitrary command and process its input, or output, as a file descriptor. In this way, you can then use diff against the output of two commands as follows
diff <(cmd1) <(cmd2)Both cmd1 and cmd2 will appear as a file name/file descriptor. The < character indicates that the file descriptor should → Continue reading “Diffing the output of two commands”
For some things, a docker container will not work. For example, I am working on a Python project to automate the deployment and configuration of VMs and bare-metal boxes. It involves installing packages and configuring the OS and to properly test it requires a full fledged VM and not just a container.
Install packer. The description straight from apt show packer is “HashiCorp Packer – A tool for creating identical → Continue reading “Creating Custom Vagrant Boxes for Integration Testing”
An easy way to parameterize a Vagrant file is to use environment variables. You simply need to export a variable and then refer to it in the Vagrant file with the following syntax.
Export the variable:
export SSH_PORT=22222Sample Vagrant file that reads the exported variable
# -*- mode: ruby -*-
# vi: set ft=ruby :
Vagrant.configure("2") do |config|
config.vm.box = "debian/bullseye64"
config.vm.box_version = "11.20221219.1"
config.vm.network "forwarded_port", guest: 22, host: ENV['SSH_PORT']
endIf you want to dynamically define and export variable names in Bash here is the TLDR;
# Define the name of the variable
key="my-dynamic-var-name"
# Declare it and export it
declare -gx "$key"="some-value"To then access that value via a dynamically generated variable name
# Create a variable that contains the variable name
var_to_access="my-dynamic-var-name"
# Read the value
my_var_value=${!var_to_access}Read the man page for declare for more details and read this article for a really good explanation and further examples.→ Continue reading “Declaring, Exporting, and Reading Dynamic Variables in Bash”
I was trying to run a Debian, Linux, guest on a Windows 11 Enterprise host with virtualization enabled for the VMWare Linux guest so that I could install minikube. Minikube requires running a VM on the host on which minikube is running, so essentially, a VM within a VM.
After enabling the “Virtualize Intel VT-x/EPT or AMD-V/RVI” setting and attempting to boot the VM it indicated that this configuration was not supported on this platform.
After quite a bit of → Continue reading “[SOLVED] ‘Virtualized Intel VT-x/EPT is not supported on this platform. Continue without virtualized Intel VT-x/EPT’ on Windows 11 host”
Sometimes you will want to ensure that a file is sourced instead of executed. This ensures, among other things, that any environment variables that the script defines remain in your current shell after the script completes.
To do so, use the following to check whether the file was sourced or run in a sub-shell
(return 0 2/dev/null) && sourced=1 || sourced=0
echo "sourced=$sourced"Bash allows return statements only from functions and in a scripts top level scope IF it → Continue reading “How to check if a file is sourced in Bash”
I have no idea why, but for some reason I always have a hard time remembering the exact syntax for find when I want to prune some list of directories from a search.
Let’s say that you want to execute a find in a directory where there are a lot of .git directories and you don’t want to search through the guts of the repo directories. With the following command we specify the prune predicate ahead of the search for → Continue reading “Pruning directories from find”
The TLDR; is to first use tr to replace all occurrences of any horizontal whitespace character with a single space, and then squeeze down any number of spaces to a single space and then define the delimiter for cut as a single space. The following example assumes that you want to see from the 5th column to the end of the line.
<do-something-to-generate-input| tr '[:blank:]' ' ' | tr -s ' ' | cut -d ' ' -f5-The → Continue reading “Using cut with a delimiter of any amount of whitespace”