file

Scala code to read a text file to an Array (or Seq)

As a quick note, I use code like this read a text file into an Array, List, or Seq using Scala:

def readFile(filename: String): Seq[String] = {
    val bufferedSource = io.Source.fromFile(filename)
    val lines = (for (line <- bufferedSource.getLines()) yield line).toList
    bufferedSource.close
    lines
}

How to use ‘awk’ to print columns from a text file (in any order)

Printing columns of information from Unix text files is easy, especially using commands like awk, perl, and more recently, ruby. This short tutorial shows my old-school awk way of doing this.

awk column printing examples

Suppose you have a file named foo with contents like this:

1 2 3
a b c

You can easily use awk to print columns of information from this file. Here are a few examples that show how to print the data columns from the file:

What is the Unix/Linux “bit bucket”?

Unix/Linux FAQ: What is the “bit bucket”?

The bit bucket is a way of referring /dev/null. Sending output to the /dev/null device file is like sending output directly to the trash. That’s why you see code like this a lot of times:

aCommand 2> /dev/null

That’s a way of saying, “Run the command aCommand and send it’s error output to the bit bucket.” In use like this, “error output” refers to STDERR, and redirecting STDERR to the bit bucket is the same as throwing it into the trash (or throwing it into a black hole, if you prefer).

Another way you can demonstrate this is by sending STDOUT to the bit bucket. In this next example, I send the output from the ls command to the bit bucket:

ls -l > /dev/null

If you run that command, you won’t see any output because the standard output — STDOUT — is redirected to /dev/null. There’s no practical reason for doing this in the real world; I just wanted to demonstrate that you can redirect both STDOUT and STDERR to the bit bucket, if you ever need to.

For more information, here’s a short tutorial on How to redirect Unix STDOUT and STDERR to the same location.

Sorting ‘ls’ command output by filesize

I just noticed that some of the MySQL files on this website had grown very large, so I wanted to be able to list all of the files in the MySQL data directory and sort them by filesize, with the largest files shown at the end of the listing. This ls command did the trick, resulting in the output shown in the image:

ls -Slhr

The -S option is the key, telling the ls command to sort the file listing by size. The -h option tells ls to make the output human readable, and -r tells it to reverse the output, so in this case the largest files are shown at the end of the output.

A Perl script to delete binary files

As a quick note and a little bit of source code sharing, I wrote the following Perl script to delete all of the binary files it finds in a list of files it’s given. I named this script deleteBinaryFiles.pl, and it should be called like this:

deleteBinaryFiles.pl listOfFilesToLookAt

where listOfFilesToLookAt is a file that contains a list of filenames, with one filename per line.

Given that brief introduction, here’s the source code:

When you want to store static text in an Android file

As a note to self, when you’re writing an Android application and you think you want to store some static text in an external file, a better approach can be to create a resource file under res/values.

For example, I’m currently adding some help text to an Android app, and to do that I created a file named strings_help.xml under the res/values directory. That file contains HTML wrapped in an XML CDATA tag, like this: