patterns

How to search for multiple regex patterns in many files with `ffx` alvin September 22, 2019 - 8:35pm

I recently created a command I named ffx that lets you search your filesystem for files that contain multiple strings or regular expressions. This post describes and demonstrates its capabilities. (There’s a little video down below if you want to see how it works before reading about it.)

Unix/Linux: Find all files that contain multiple strings/patterns

When using Unix or Linux, if you ever need to find all files that contain multiple strings/patterns, — such as finding all Scala files that contain 'try', 'catch', and 'finally' — this find/awk command seems to do the trick:

find . -type f -name *scala -exec awk 'BEGIN {RS=""; FS="\n"} /try/ && /catch/ && /finally/ {print FILENAME}' {} \;

As shown in the image below, all of the matching filenames are printed out. As Monk says, you’ll thank me later. :)

(I should mention that I got part of the solution from this gnu.org page.)

A Scala Factory Pattern example

Here’s a small example of how to create a Factory Pattern in Scala. In the Scala Cookbook I created what some people might call a simple factory and/or static factory, so the following code is a much better implementation of a true OOP Factory Pattern.

The factory classes

I don’t have too much time to explain the code today, but here are the classes that make up the factory, including a set of “animal” classes along with a DogFactory and CatFactory that extend an AnimalFactory trait:

Scala: How to extract parts of a String that match regex patterns

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 1.9, “Extracting Parts of a String that Match Patterns.”

Problem

You want to extract one or more parts of a Scala String that match the regular-expression patterns you specify.

Solution

Define the regular-expression (regex) patterns you want to extract, placing parentheses around them so you can extract them as “regular-expression groups.” First, define the desired pattern:

How to find regex patterns in Scala strings

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 1.7, “Finding Patterns in Scala Strings.”

Problem

You need to determine whether a Scala String contains a regular expression pattern.

A custom TextMate command that uses ‘sed’

In this post I share the contents of a custom TextMate command I just created that uses pandoc and sed to convert markdown content in the TextMate editor to a “pretty printer” version of HTML:

#!/bin/sh

PATH=$PATH:/usr/local/bin

# note: 'sed -E' gives you the advanced regex's

# use pandoc to convert from markdown to html,
# then use sed to clean up the resulting html
pandoc -f markdown -t html |\
sed -Ee "/<p|<h2|<h3|<h4|<aside|<div|<ul|<ol/i\\
\\"

You can try to use a command like tidy to clean the HTML, but the version of tidy I have does not know about HTML5 tags. The TextMate Markdown plugin also doesn’t work the way I want it. Besides that, I’m trying to learn more about writing TextMate commands anyway.

As an important note, when you set this up as a TextMate command and then run it, it will convert the TextMate editor contents from markdown to HTML.

(In a related note, serenity.de is also a good resource for TextMate command and bundle documentation.)

In summary, this code shows:

* How to execute a Unix shell command from TextMate
* Specifically, how to execute a sed command from TextMate
* How to use modern regular expressions with sed (the -E option)
* How to search for multiple regex search patterns with sed

The Mediator Design Pattern in Java

Summary: The Mediator Design Pattern is demonstrated in a Java example (a Java Mediator Pattern example).

Android UI design guidelines links

Google has a nice Android UI design guidelines section on the Android website. As I'm working on a new Android tablet application, I keep looking back at this section, and these are the most relevant pages for me:

Design Patterns in Java

I've recently started writing a series of articles on Design Patterns in Java, i.e., Design Patterns explained using Java source code examples. Although it will take me a little while to create each design pattern example, this page will eventually contain links to all of those examples.

If you're not familiar with software design patterns, they're described on Wikipedia like this: