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Joining multiple PDFs together on Linux

Submitted by Druss on Wed, 2015-08-26 22:44

A quick and easy way to join or merge multiple PDFs together on Linux (Kubuntu 14.10):

pdfunite toc.pdf chapter1.pdf chapter2.pdf  book.pdf

This doesn't resample pages or any other nonsense like that either :) pdfunite is provided by the poppler-utils package which should already be installed.

If you want to do the opposite, i.e. split a unified PDF file into multiple ones, poppler-utils also provides the aptly named pdfseparate.

Hope this helps :)

Sed: invalid reference \1 on `s' command's RHS

Submitted by Druss on Mon, 2015-07-06 13:46

If you see something like the following error message when you run a sed command:

invalid reference \1 on `s' command's RHS

then it (probably) means that your regex capture group has not been escaped properly.

So, if you are using a command like:

sed "s/foo(bar)[123]/baz\1/"

then it needs to be escaped like so:

sed "s/foo\(bar\)[123]/baz\1/"

In other words, round parentheses/brackets need to be escaped while the square brackets do not :|

Mouse Marks: Weird red marks on screen when pressing the Windows Meta Key and Shift

Submitted by Druss on Fri, 2015-03-20 18:36

For the last few weeks, I've noticed weird red dots/lines or similar marks on my Kubuntu screen. I'd attributed them to a graphics issue that I'd recently sorted out, particularly because I was mainly noticing these marks when resuming the system from sleep mode. Turns out I was wrong. Very wrong.

Resuming after sleep mode, terminating/hanging up a frozen SSH session in Linux

Submitted by Druss on Fri, 2015-03-20 11:55

So, I am often SSH'd into a remote server from my Kubuntu desktop. I also rarely switch off my desktop and prefer to just hit sleep instead. One of the things that can be annoying when I resume the desktop is that the previous SSH session is now unresponsive/frozen as SSH believes that it is still connected to the remote server while the server has given up on the old session long ago. No amount of CTRL + C or CTRL + Z banging is going to terminate the session which can take an inordinately long wait to time out.

Kubuntu: Audio plays in the wrong tty/terminal

Submitted by Druss on Thu, 2015-03-05 01:18

This has happened to me on a number of occasions where I've found that my system audio only plays when I switch to a different tty. I don't know exactly how to duplicate the issue . But essentially, if I switch from my Kubuntu 14.10 KDE desktop to a different tty (using something like CtrlAltF5) and then switch back to the KDE tty, I find that I can hear no audio. However, if I switch again to the command-line tty, I can hear that audio that ought to have been playing in KDE. Rather weird, huh?

Typing an ellipsis and other exotic characters in KDE/Kubuntu

Submitted by Druss on Wed, 2015-02-18 20:11

I can sometimes be rather picky (some would say 'anal') when I write, for example, an e-mail. I get annoyed if I have to resort to typing three periods for an ellipsis rather than achieving it with just the one character. Doing something with one character instead of three is also a skill that has carved itself a niche in this age of Twitter. So how would one go about it?

Upgrading the Linux kernel in Kubuntu 14.10 from 3.16 to 3.19

Submitted by Druss on Tue, 2015-02-17 02:02

So I've had a graphics issue with my Kubuntu box which relies on an Intel motherboard. While I was hoping to put off the fix until the next version of Kubuntu (out in April), the display bug was getting to be really annoying. I therefore decided to upgrade to the latest kernel immediately.

Google Chrome status bar no longer appearing on hover

Submitted by Druss on Mon, 2015-02-16 19:04

So I upgraded my Kubuntu box's kernel to 3.19 and while that fixed my graphics issues, I ran into a new and peculiar issue where hovering over links in Google Chrome failed to display the linked addresses in the bottom of the screen (the status bar). This is apparently a known (Chromium) bug which has still not been resolved. The current recommended workaround is to disable and re-enable hardware acceleration as follows:

Desktop effects were restarted due to a graphics reset

Submitted by Druss on Wed, 2015-02-04 01:43

While using Google Chrome on Kubuntu 14.10, the display hung for about 5 seconds before unfreezing with the following notification:

Desktop effects were restarted due to a graphics reset

Once this began occurring with an increasing frequency, I began to do a little digging. Looking through /var/log/kern.log brought the following up:

Eclipse Luna: java: /build/buildd/gtk2-engines-oxygen-1.4.5/src/animations/oxygencomboboxdata.cpp:87: void Oxygen::ComboBoxData::setButton(GtkWidget*): Assertion `!_button._widget' failed.

Submitted by Druss on Mon, 2015-02-02 18:03

After installing the shiny new version of Eclipse entitled 'Luna' on a Kubuntu 14.10 box, I found that it crashed/hung when trying to import/clone a Git repository. Starting the application from the command-line triggered the following notice before the crash:


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