The gedit bug with Shared Folders in VirtualBox – a Workaround

The trouble with a Virtual Machine is that it’s, well, virtual. Sooner or later, you’re going to want to transfer some files back to the host.

Unfortunately, gedit seems to have a bit of a problem getting it’s head around this process. When you do try to change a file in the shared directory, gedit complains :

Could not save file path to file on shared folder
Unexpected error: Error renaming temporary file : Text file busy

All is not lost however. Yes, this does appear to be a bug, but there is a solution that will enable you to continue using your favourite Gnome editor inside Virtual land.
For this you will need :

  • a local folder on the Guest OS
  • a shell script
  • an alias in .bashrc
  • some sticky-back plastic

OK, so I made that last one up. Continue reading

Twiddling with tar – Differential backups on Linux

When I first mentioned the title of this post to my girlfriend, she misheard and thought there was an extra “t” at the end.
One hasty explanation later I have avoided banishment to the shed. All of which is mildly ironic as the tar command comes with a whole alphabet of options, many of which are about to get used here.

As it’s name suggests, the venerable tar command ( Tape ARchive) has it’s roots back in the time when computers were the size of a small semi in Dagenham and punch cards and tapes were the acme of the Programmer’s art.

Now I’m going to use it for backing up data on my assorted Ubuntu machines.
What I want to do here is :

  • work out how much data I need to backup
  • create a full backup of all of my data
  • make sure I know what files have been backed up
  • test the restore of a file from the backup
  • make subsequent incremental backups

In the course of this odyssey, we will discover that du has a human face and that tar has a bit of a yellow streak.
There are several things that can go horribly wrong when playing around with tar, so I’m going to test everything on a small subset of files…that I have safely stored elsewhere.
Speaking of which… Continue reading

Zen and the Art of Shell Scripting

You know what it’s like with a little kid at his birthday party. They get all excited, eat far too many sugary foods and then run around behaving badly.
Oracle Openworld has ended for another year, and not a minute too soon. Hopefully, Larry will have an early night and stop being so excitable and upsetting all those jolly nice open source types he had round.
Meanwhile, in the comparative calm of the backwater that is this blog, I’ve been getting all Zen. Well, zenity, to be precise. Yep, I’ve decided that some my batch scripts needed to get all GUI with Gnome and zenity looks to be the tool to do it.
What follows is an account of my first steps with zenity followed by a demonstration of some of it’s capabilities. Continue reading

Windows Bashing…with Cygwin

I was in Wales last week, land of my girlfriend ( yes, I have got one, try not to look so shocked).
Wales, land of story and legend….where the rain goes for it’s summer holidays.

Stepping gingerly between the puddles in picturesque ( albeit, soggy) Laugharne, we spent an instructive ( and mainly dry) hour or so at the boathouse once occupied by Dylan Thomas. In the course of this cultural interlude, I learned that the Great Man’s last words were “ I’ve had 18 straight whiskys. I think that might be the record.”

Hmmm, I wonder if he’d been trying to write a Windows batch script ?

Whatever the merits of Windows in terms of it’s ubiquity, one undeniable fact is that the facilities provided for batch scripting on the command line are stone-age compared to those in Unix.
This is something I’ve often reflected on, usually when confronted with a problem that requires a bit more than a simple for loop.

Help is at hand however, in the form of Cygwin – a toolset which enables you to more-or-less run a bash shell on Windows. Sounds good to me. Let’s have a look…. Continue reading

Getting the Quiz Machine to Pay Out – talking to your database from a shell script

I was in the pub the other day with my mate Simon. It’s surprising just how many of my posts have their genesis in such a setting. For the benefit of any prospective employers ( and my Mum), I put this down to the company and the mental stimulation of working out just exactly how you collect your winnings from the Quiz Machine.
For anyone who does not have first-hand experience of English Pub Quiz machines, the trick is either to a) get the barman to pay you from the till or b) have about your person a rather large hammer.

Fortunately, the hammer wasn’t required on this particular occasion, which is just as well as neither of us had brought one ( it’s not really that kind of pub). The reason for our lack of success eventually became apparent. After a conversational odyssey through the Bedfordshire countryside (the vicissitudes of Luton Town) via Table Mountain (England’s prospects for the World Cup), Simon – definitely the brains of the operation in Quiz Machine terms – confessed to wrestling with one of those perennial problems that are an occupational hazard of the Database Specialist’s art.

Yes, as well as being a bit of a whizz on the Science and Nature stuff, Simon is a long-time Teradata expert. Continue reading