command

Linux backups: Using find, xargs, and tar to create a huge archive

I did something wrong in a previous blog entry that led me to use the pax command to create a large backup/archive. There’s nothing wrong with using pax — other than the fact that it’s not available for Cygwin — and I really needed to created a huge archive.

What wasn’t working

In my earlier blog post I stated that something like this did not work for me when trying to create a large backup using find, xargs, and tar:

find . -type f -name "*.java" | xargs tar cvf myfile.tar

What was happening was that as xargs was managing the input to the tar command, tar kept re-writing the archive. That is, each time xargs passed a new block of input files to tar, tar perceived it as a new command, and went on to re-create the file named myfile.tar. So, instead of the huge myfile.tar that I expected, I ended up with only a few files in the archive.

A big collection of Unix/Linux 'find' command examples

Linux/Unix FAQ: Can you share some Linux find command examples?

Sure. The Unix/Linux find command is very powerful. It can search the entire filesystem to find files and directories according to the search criteria you specify. Besides using the find command to locate files, you can also execute other Linux commands (grep, mv, rm, etc.) on the files and directories you find, which makes find extremely powerful.

An initial thought when taking the time to create a new app or utility

Sometimes when I embark on little projects like my Scala file-find command, I think, “This is a waste of time, the existing tools are good enough.” But then, if I’m motivated enough — if I really want something — I think, “But I can use this better tool for the rest of my life...”

I just released the file-find command four days ago, and I use it almost every day while learning Flutter and Dart, so I think it’s going to be well worth it.

My new `sbtmkdirs` command alvin August 28, 2019 - 12:03pm

Motivated by GraalVM, I rewrote my sbtmkdirs command using Scala. Here’s a link to the new Scala `sbtmkdirs` project on Github.

How to run shell commands from the Scala REPL

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 14.4, “How to run a shell command from the Scala REPL.”

Problem

You want to be able to run a shell command from within the Scala REPL, such as listing the files in the current directory.

Solution

Run the command using the :sh REPL command, then print the output. The following example shows how to run the Unix ls -al command from within the REPL, and then show the results of the command:

A shell script to change between MacOS dark mode and light mode

If you want to create a shell script so you can change between MacOS dark mode and light mode from the Terminal (Unix) command line, put this source code in a file and name it something like dark:

osascript -e \
'tell application "System Events" to tell appearance preferences to set dark mode to not dark mode'

Then make that file executable, and make sure it’s on your PATH. Now you can type dark to toggle back and forth between dark mode and the regular light mode:

How can I tell what version of SBT my project is using? alvin December 27, 2018 - 1:44pm

At the moment this is kind of funky, but I find that the best way to determine the version of SBT is to move to a temporary directory and then run the sbt sbtVersion command:

Scala: How to give SBT more memory (RAM) to work with

As a brief note, I was trying to run a Scala application inside SBT today and kept getting this “out of memory” error:

[error] (run-main-0) java.lang.OutOfMemoryError: GC overhead limit exceeded
java.lang.OutOfMemoryError: GC overhead limit exceeded

The solution to the problem was to allocate more memory when I start SBT. To give SBT more RAM I first issue this command at the command line: