shell script

How to start a Play Framework application running as a service on Ubuntu 16.04 alvin April 30, 2018 - 6:17pm

As a relatively brief note, this seems to be the correct way to start a Play Framework application as a service on an Ubuntu 16.04 system.

A shell script to start your Play application

First, you need to create a little Unix shell script that runs the startup command for your Play Framework application. I created a Play application for a website named kbhr.co, so I cd into the directory for that website:

A Play Framework 2.6 startup script example (Scala)

Play Framework FAQ: Can you share an example of a Play Framework 2.6 startup script, i.e., a shell script that shows the commands and parameters you use to run a Play Framework application?

Sure. Assuming that you created a production mode version of your application with the sbt dist command, deployed that zip file to a production server, and have a Play Framework 2.6 application named “myapp,” you can put a command like this in a Unix/Linux shell script to start your Play application:

A Scala shell script to insert text before a matching pattern alvin February 7, 2018 - 4:25pm

I don’t remember exactly why I wrote this Scala shell script, but if I remember right I was having a problem getting sed to work properly, so I wrote this little script to insert an Amazon Kindle “break” tag before each <h1> tag in an HTML file:

A Scala “Word of the day” shell script alvin February 5, 2018 - 3:39pm

I have a 19" monitor on the counter between my kitchen and living room, and it’s powered by a Raspberry Pi. I use the Linux Phosphor screen saver to show a scrolling “news and stock ticker” on the display, which I’ve programmed to show news from several different sources (Atom and Rss feeds, along with other news and data sources). An old version of the display looks like this:

My Raspberry Pi news ticker display

Today I added a new “Word of the day” feature to the display, and as with all of the other code, I wrote a Scala shell script to generate the output.

Linux: How to get the basename from the full filename alvin January 1, 2018 - 3:21pm

As a quick note today, if you’re ever writing a Linux shell script and need to get the filename from a complete (canonical) directory/file path, you can use the Linux basename command like this:

$ basename /foo/bar/baz/foo.txt
foo.txt
How to write a Scala shell script that reads input from STDIN alvin October 29, 2017 - 1:52pm

As a quick note, if you need an example of how to write a Scala shell script that reads from STDIN (standard input) and writes to STDOUT (standard output), this code shows a solution:

#!/bin/sh
exec scala -savecompiled "$0" "$@"
!#

import scala.io.StdIn

var line = ""
while ({line = StdIn.readLine(); line != null}) {
    println(line)
}
A Scala shell script to read HTML H1 tag attributes alvin October 20, 2017 - 3:14am

I’m putting this Scala shell script out here as a “source code snippet” so I can find it again if I need it. This file reads an input file that contains a series of HTML <h1> tags. I use this as part of a process of publishing an Amazon Kindle ebook from an HTML file, and in one of the steps of the creation process, I use this script to help create the Table of Contents (TOC) for the book.

Here’s the source code:

How to process every line in a file with a Unix/Linux shell script

Unix/Linux shell script FAQ: How do I write a Unix or Linux shell script where I "do something" for every line in a text file?

Solution: An easy way to process every line in a text file is to use a Unix/Linux while loop in combination with the Linux cat command, like this:

A Linux shell script (and commands) to find large files alvin July 14, 2017 - 11:14am

I made a mistake in configuring logrotate on a new Linux system, and almost ran into a problem because of that. Fortunately I saw the problem before it became a BIG problem, but as a result, I decided to add a script to my Linux system to check for large files, typically log files that have grown out of control for one reason or another.

Here then is a simple Linux shell script I named LargeFileCheck.sh, which searches the filesystem for files that are larger than 1GB in size: