Category: Computers

All things computing.

Unit Testing Private Static Methods With Primitive Array Arguments

Posted on by rchapin

When writing unit tests to cover your entire program you will undoubtedly come across the need to test private methods.  There are arguments that these methods should be tested via integration tests, but there are sometimes when it makes more sense to test all of the permutations in a unit test. This can be achieved using reflection in Java JUnit tests.

What is a little tricky, and was not completely obvious, was how to use reflection to test a private → Continue reading “Unit Testing Private Static Methods With Primitive Array Arguments”

One-Liner for Converting CRLF to LF in Text Files

Posted on by rchapin

If you have text files created under DOS/Windows and need to convert the CRLF (carriage return and line feed) characters to LF (line feed) character, here is a quick one-liner.

cat file.txt | perl -ne 's/\x0D\x0A/\x0A/g; print' file.txt.mod

You can also use dos2unix, however, especially under Cygwin I have seen dos2unix fail without giving any meaningful information about why it was unable to complete the task.  In that case, you can just do it by hand. → Continue reading “One-Liner for Converting CRLF to LF in Text Files”

Configuring Eclipse to Replace Tabs with Spaces for Indentation

Posted on by rchapin

Following are two basic settings (I believe that there are other language specific, C++ for instance, settings as well).

 For Java:

Window->Preferences->Java->Code Style->Formatter->
Click on ‘New’ to create a new profile and select the profile that you want to copy
Then click ‘Edit’ and select ‘Spaces Only’ from the ‘Tab Policy’ dropdown.

You can further set the indentation and tab size.

For default text editor:

Window->Preferences->General->Editors->Text Editors->Insert spaces for tabs→ Continue reading “Configuring Eclipse to Replace Tabs with Spaces for Indentation”

Parsing Command Line Arguments with getopt in Bash

Posted on by rchapin

When writing utility scripts in Bash it is tempting to simply pass positional arguments, use $1, $2, etc. and be done with it.  However if you want to either share this utility with other members of your team and/or incorporate it into your system, it makes sense to implement your command line argument parsing in a more flexible and maintainable manner.

Using getopt you can very easily pass a variety of command line options and arguments.

Following is a link → Continue reading “Parsing Command Line Arguments with getopt in Bash”

Passing an Array as an Argument to a Bash Function

Posted on by rchapin

If you want to pass an array of items to a bash function, the simple answer is that you need to pass the expanded values.  That means that you can pass the data as a quoted value, assuming that the elements are whitespace delimited, or you can pass it as a string and then split it using an updated IFS (Internal Field Separator) inside the function.

Following is an example of taking the output of a Hive query (a single → Continue reading “Passing an Array as an Argument to a Bash Function”

Restarting Individual Services or the Entire HDP Stack in the Hortornworks Virtual Sandbox

Posted on by rchapin

I’m using the Hortonworks Virtual Sandbox for development and testing and wanted to restart the HDP stack without (of course) having to restart the VM.

It took me a little while to figure out how to go about it as Internet searches on the topic revealed very little.

It turns out that Hortonworks have set up their own service on the box, startup_script.

If you take a look at /etc/init.d/startup_script you will see that it calls a number of other → Continue reading “Restarting Individual Services or the Entire HDP Stack in the Hortornworks Virtual Sandbox”

Vim Search and Replacing with Backreferences

Posted on by rchapin

It is often helpful to write search and replace commands that save segments of the matched text to use in the replacement string.

Source text:

This is some text (we want to change) with a phone number (301) 555-1234.
We want to remove the parenthesis, but only from the phone number string.

In this example we have a text file that has a phone number in it and we want to remove the parenthesis that surround ONLY the area code → Continue reading “Vim Search and Replacing with Backreferences”

Print Lines in a File From a Specific Line Number Until the End of the File with sed

Posted on by rchapin

If you know that you want all of the lines in a given file from n to EOF the following is the sed command:

sed -n '3,$p' some_file.txt

To print out lines 2 – 5 simply modify it to:

sed -n '2,5p' some_file.txt

→ Continue reading “Print Lines in a File From a Specific Line Number Until the End of the File with sed”

Removing the Last Token From a String in Bash with awk

Posted on by rchapin

Let’s say that you have some number of files for which you want to create a containing directory that is named with all but the last token of the file name, and you want to remove just the last token to create the name of the directory.

Much easier to explain with an example.  Given this list of files:

ls -1
foo_10_10_sometrash
foo_1_sometrash
foo_2_sometrash
foo_3_sometrash
foo_4_sometrash
foo_5_5_sometrash
foo_5_sometrash
foo_6_6_sometrash
foo_7_7_sometrash
foo_8_8_sometrash
foo_9_9_sometrash

You want to create a directory for each → Continue reading “Removing the Last Token From a String in Bash with awk”

© 2005 Ryan Chapin