peterwwillis

Awk

Print only the first part of a file separated by two newlines

Note that this uses tr to remove any carriage-returns (as in "\r\n" from Windows or network programs)

# Print only the block of lines before the first double-newline
cat file.txt | tr -d '\r' | \
  awk 'BEGIN {RS="\n\n"} NR==1'
 

peterwwillis

If you try to copy a source directory into a symlink to a target directory, you may get an error like: cp: cannot overwrite non-directory 'symbolic-link' with directory 'source'.

The solution is to actually copy the . directory of your source directory. This is not obvious based on the GNU coreutils FAQ or the man page.

Below is an example to explain:

vagrant@devbox:~/foo$ mkdir bin

peterwwillis

Set up Ubuntu Linux to use Active Directory for user authentication + authorization

This guide will step you through setting up an Ubuntu 18.04 Linux system so that you can login to it using an Active Directory server for authentication and authorization. NOTE: You do not need to join a domain to use this method!!

The net effect of this guide is that you do not need to ever set up a user on your Linux host. Its home directory will be automatically created at log-in time, and its password is checked (along with account expiration) against the Active Directory server.

peterwwillis

Tips and Best Practices for programming in C

Syntax

Tips

• You can explain a complicated declaration in English using cdelc.
  • echo "explain char *(*pfpc)()" | cdecl
  • https://cdecl.org/

Data Structures / Types

peterwwillis

Run commands

Use Docker to build a Jenkins plugin

1. Check out a Jenkins plugin from GitHub

   $ git clone git@github.com:jenkinsci/configuration-as-code-secret-ssm-plugin.git
   $ cd configuration-as-code-secret-ssm-plugin

2. Build the plugin. Change the maven tag to something like 3-jdk-8 or 3-jdk-11 if you run into errors, as some plugins only build with one JDK version.
   • Run as a non-root user

peterwwillis

// from https://stackoverflow.com/questions/9815273/how-to-get-a-list-of-installed-jenkins-plugins-with-name-and-version-pair#12730830
// the sort version doesn't seem to work on my jenkins install
Jenkins.instance.pluginManager.plugins.each{
  plugin -> 
    println ("${plugin.getDisplayName()} (${plugin.getShortName()}): ${plugin.getVersion()}")
}

peterwwillis

About

This document explains how to use the Unix tool pass to manage passwords.

Using pass

Initial set-up

1. Install software

• Install pass: https://www.passwordstore.org/#download
• Install gpg
• Ubuntu: $ sudo apt-get install gnupg2

peterwwillis

// To support more types of credentials, look up the credentials plugin code and write
// additional groovy to parse those credential types.
// 
// From Mohamed Saeed: https://medium.com/@eng.mohamed.m.saeed/show-all-credentials-value-in-jenkins-using-script-console-83784e95b857

def creds = com.cloudbees.plugins.credentials.CredentialsProvider.lookupCredentials(
    com.cloudbees.plugins.credentials.common.StandardUsernameCredentials.class,
    Jenkins.instance,
    null,
    null

peterwwillis

#!/bin/sh
set -e
_get_cert () {
  openssl s_client -showcerts -connect "$1":"$2" </dev/null 2>/dev/null | openssl x509 -outform PEM 
}
if [ $# -lt 2 ] ; then
  echo "Usage: $0 HOST PORT [OUTFILE]"
  echo ""
  echo "Connects to TCP PORT on HOST and downloads TLS certificates."
  echo "Saves to OUTFILE if it is specified, otherwise outputs to standard out."

peterwwillis

#!/bin/sh
# defaultenv.sh - Load environment variable defaults and run programs

set -e
[ x"$DEBUG" = "x1" ] && set -x

_load_envrc () {
    local file="$1"; shift
    if [ -r "$file" ] ; then
        # Bourne shell limits how we can test and set env vars, so here I'm