Adventures & experiences in contemporary technology
There is a handy comand line utility called GNU Parallel that allows you to run Linux commands on more than one CPU core at a time to perform parallel processing of the task at hand. Here is a form of the command that is similar to one that I often use:
ls *.* | parallel gm convert -sharpen 1×3 {} sharpened_images/{}
What it does is pipe a list of files in a folder to GraphicsMagick for sharpening and outputting to a sharpened_images directory. The {} in the command is where the filenames go in the sharpening command.
This worked fine in Ubuntu GNOME 12.10 but stopped doing so after I upgraded to the next version. A look on the web set me to running the following command:
parallel --version
That produced output that included the following line:
WARNING: YOU ARE USING --tollef. IF THINGS ARE ACTING WEIRD USE --gnu.
Rerunning the original command with the --gnu option worked but there was a more permanent solution than using something like this:
ls *.* | parallel --gnu gm convert -sharpen 1×3 {} sharpened_images/{}
That was editing /etc/parallel/config with root privileges to delete the --tollef option from there. With that completed, all was as it should again and it makes me wonder why the change was made in the first place. Perhaps because of it, there even is a discussion about the possibility of removing the --tollef option altogether since it is raising more questions than it answers.
There is a bill making its way through the U.K. parliament at the moment that could reduce the power of copyright when it comes to images placed on the web. The current situation is that anyone who creates an image automatically holds the copyright for it. However, the new legislation will remove that if it becomes law as it stands. As it happens, the Royal Photographic Society is doing what it can to avoid any changes to what we have now. There may be the barrier of due diligence but how many of us take steps to mark our own intellectual property? For one, I have been less that attentive to this and now wonder if there is anything more that I should be doing. Others may copyleft their images but I don’t want to find myself unable to share my own photos because another party is claiming rights over them. There’s watermarking them but I also want to add something to the image metadata too.
That got me wondering about adding metadata to any images that I post online that assert my status as the copyright holder. It may not be perfect but any action is better than doing nothing at all. Given that I don’t post photos where EXIF metadata is stripped as part of the uploading process, it should be there to see for anyone who bothers to check and there may not be many who do.
Because I also wanted to batch process images, I looked for a command line tool to do the needful and found ExifTool. Being a Perl library, it is cross-platform so you can use it on Linux, Windows and even OS X. To install it on a Debian or Ubuntu based Linux distro, just use the following command:
sudo apt-get install libimage-exiftool-perl
The form of the command that I found useful for adding the actual copyright information is below:
exiftool -p “-copyright=(c) John …” -ext jpg -overwrite_original
The -p switch preserves the timestamp of the image file while the -overwrite_original one ensures that you don’t end up with unwanted backup files. The copyright message goes within the quotes along with the -copyright option. With a little shell scripting, you can traverse a directory structure and change the metadata for any image files contained in different sub-folders. If you wish to do more than this, there’s always the user documentation to be consulted.
At some point, I managed to lose the ability to have tab key based autocompletion on terminal sessions on my Ubuntu GNOME machine. Wanting it back had me turn to the web for an answer and I found it on a Linux Mint forum; the bash shell is so pervasive in the UNIX and Linux worlds that you can look anywhere for a fix like this.
The problem centred around the .bashrc file in my home area. It does have quite a few handy custom aliases and I must have done a foolish spring clean on the file sometime. That is the only way that I can explain how the following lines got removed:
if [ -f /etc/bash_completion ]; then
. /etc/bash_completion
fi
What they do is look to see if /etc/bash_completion can be found on your system and to use it for tab-based autocompletion. With the lines not in .bashrc, it couldn’t happen. Others may replace bash_completion with bash.bashrc to got a fuller complement of features but I’ll stick with what I have for now.
Linux and UNIX have the touch command for changing the creation dates and times for files. However, it also will create empty text files for you as well. In fact, there are times when I feel the need to do this sort of thing on Windows too and the following command accomplishes the deed when run in a Command Prompt window:
type nul > command.bat
Essentially, null output is sent to a file that is created anew, command.bat in this case. Then, you can edit it in Notepad (or whatever is your choice of text editor) and add in what you need. This will not work in Powershell so you need another command for that:
New-Item command.bat -type file
This uses the New-Item command, which also can be used to create folders as well if you so desire. Then, the command becomes the following:
New-Item c:\commands -type directory
Note that file on the previous example has become directory and there is the -force option should you need to overwrite what already exists for some reason…
That other use of the UNIX/Linux touch command can be performed from the Command Prompt too and here is an example command:
copy /b file.txt +,,
The /b switch switches on binary behaviour for the copy command though that appears to be the default action anyway. The + operator triggers concatenation and ,, gets around not having a defined destination because you cannot copy a file over itself. If that were possible, then there would no need for special syntax for changing the date and time for a file.
For doing the same thing with Powershell, try the following:
(GetChildItem test.txt).LastWriteTime=Get-Date
The GetChildItem command has aliases of gci, dir and ls and the last two of these give away its essential purpose. Here, it is used to pick out the test.txt file so that its timestamp can be replaced with the current date and time returned by the Get-Date command. The syntax looks a little more complex even if it achieves the same end. Somehow, that touch command is easier to explain. Are Linux and UNIX that complicated after all?
While UNIX and Linux both have the diff command for comparing the contents of text files, the Windows counterpart was unknown to me until recently. Its name is fc and it looks as if the f is for file and c is for comparison though I cannot confirm that as of now. That command and its usage is not dissimilar to the way that things work with diff. Here is an example command:
fc file1.txt file2.txt > file3.txt
This compares file1,txt with file2.txt and sends the output to file3.txt. Any differences between the two files being compared seem to be more clearly labelled than in the diff output’s < and > labels. That verbosity could have its uses but existence of the fc command is stopping envious glances at the diff one for now, just as findstr is doing the same in comparison with grep.
The Linux and UNIX command mv has a number of limitations, such as not overwriting destination files and not renaming multiple files using wildcards. The only solution to the first that I can find is one that involves combining the cp and rm commands. For the second, there’s another command: rename. There is a command like it in Windows but this one is a little different in its syntax. Before saying more about that, here’s an example like what I used recently:
rename s/fedora/fedora2/ fedora.*
The first argument in the above command is a regular expression much like what Perl is famous for implementing; in fact, it is Perl-compatible ones (PCRE) that are used. The s before the first slash stands for substitute with fedora being the string that needs to be replaced and fedora being what replaces it. The third command is the file name glob that you want to use, fedora.* in this case. Therefore, all files in a directory named fedora will be renamed fedora2 regardless of the file type. The same sort of operation can be performed for all files with the same extension and it needing changing, htm to html, for instance. Of course, there are other uses but these are handy ones to know.
Unless you have access to SAS Enterprise Guide, being able to work on one project at a time can be a little inconvenient. It is possible to open up more than one Display Manager System (DMS, the traditional SAS programming interface) session at a time but you can get a pop up window for SAS documentation for second and subsequent sessions and you don’t get your settings shared across them either.
The cause of both of the above is the locking of the SASUSER directory files by the first SAS session. However, it is possible to set up a number of directories and set the -sasuser option to point at different ones for different sessions.
On Windows, the command in the SAS shortcut becomes:
C:\Program Files\SAS\SAS 9.1\sas.exe -sasuser "c:\sasuser\session 1\"
On UNIX or Linux, it would look similar to this:
sas -sasuser "~/sasuser/session1/"
The “session1” in the folder paths above can be replaced with whatever you need and you can have as many as you want too. It might not seem much of a need but synchronising the SASUSER folders every now and again can give you a more consistent set of settings across each and you don’t get intrusive pop up boxes or extra messages in the log either.
The last few weeks have seen me poking around with a few different operating systems to see how they perform. None of these were particularly in-depth in their nature but brushes with alternatives to what I currently use for much of the time. While I am too sure what exactly has kicked off all of this curiosity, all of the OS’s that I have examined have been of the UNIX/Linux variety. With the inclusion of Unity in the forthcoming Ubuntu “Natty Narwhal” 11.04, I am mindful of the need to be keeping an eye on alternative options should there ever be a need to jump ship. However, a recent brush with an alpha version has reassured me a little. Then there are interesting OS releases too and I recently forgot the Ubuntu password (a silly thing to do, I know) for my Toshiba laptop too so I suppose that a few things are coming together.
It was that latter development that got me looking in amazement at the impressive minimalism of CrunchBang Linux before settling on Lubuntu to see how it did; these were Live CD runs so I tried before I committed to installing. It helped that the latter was based on Ubuntu as its name suggests so I wasted little name in finding my way around the LXDE desktop. By default, everything supplied with the distro is lightweight with Chromium coming in place of Firefox. There’s no sign of OpenOffice.org either with offerings like Abiword coming in its stead. For the sake of familiarity, I started to add the weight of things without reducing the speed of things, it seems. Well, the speedy start-up wasn’t afflicted anyway. Being an Ubuntu clone meant that it didn’t long to add on Firefox using the apt-get command. LibreOffice was downloaded for installation using the dpkg command and it seems much more fleet-footed than its OpenOffice.org counterpart. As if these nefarious actions weren’t enough, I started to poke in the settings to up the number of virtual desktops too. All in all, it never stopped me going against what be termed the intent of the thing. In spite of what Linux User & Developer has had to say, I think the presentation of the LXDE desktop isn’t unpleasant either. In fact, I reckon that I quite like it and the next thing to do is to restore the entry for Windows 7 on the GRUB menu. Well, there’s always somthing that needs doing…
While I may have learned about it after the event, the release of Debian “Squeeze” 6.0 was of interest to me too. Well, I have used it a fair bit in the last few years and retain a soft spot for it. The new release comes on two kernels: GNU/Linux and FreeBSD. Regarding the latter, I did try having a look but it locked up my main home PC when I tried booting it up in a VirtualBox virtual machine. Given that it’s a technical preview anyway, I think it better to leave it mature for a while no matter how fascinating the prospect may be. Or is it VirtualBox 4.x that hasn’t around long enough? Debian’s latest Linux incarnations showed no such inclinations though I found that the CD ISO image that I’d downloaded didn’t give such a complete system when I fired it up after doing the installation. Being someone that knows his way around Linux anyway, it was no problem to add the missing pieces using apt-get though that’d stop it being an option for new users unless the DVD installation yields more complete results. Other than that, it worked well and I lost no time getting to grips with the OS and it’s gained a much fresher feel than version 5.x (“Lenny”). In summary, I look forward to continuing my investigations of the new Debian.
To round up my explorations of different UNIX/Linux operating systems, I have updated my test installations of Ubuntu 11.04. Initial looks at the next Ubuntu release weren’t so encouraging but things are coming along by all accounts. For one thing, Unity can be switched off in favour of the more familiar GNOME desktop that we’ve had for the last few years. The messages that popped up telling you that there’s no 3D graphics support on your machine have been replaced by graceful degradation to the GNOME and that’s no bad thing either. In case it hasn’t been so obvious, I am one of those who needs convincing by the likes of Unity and GNOME Shell so I’ll sit on the fence for a while. After all, there always are alternatives like LXDE if I want to decamp to something else entirely. One of the nice things about Linux is the amount of that we all have; it might be tricky to choose sometimes but it always is good to be able to find a niche somewhere else when someone makes a decision that doesn’t suit you.
It’s amazing what work can bring your way in terms of technology. For me, (GNU) Emacs Has proved to be such a thing recently. It may have been around since 1975, long before my adventures in computing ever started, in fact, but I am asking myself why I never really have used it much. There are vague recollections of my being aware of its existence in the early days of my using UNIX over a decade ago. Was it a shortcut card with loads of seemingly esoteric keyboard shortcuts and commands that put me off it back then? The truth may have been that I got bedazzled with the world of Microsoft Windows instead, and so began a distraction that lingered until very recently. As unlikely as it looks now, Word and Office would have been part of the allure of what some consider as the dark side these days. O how OpenOffice.org and their ilk have changed that state of affairs…
The unfortunate part of the Emacs story might be that its innovations were never taken up as conventions by mainstream computing. If its counterparts elsewhere used the same keyboard shortcuts, it would feel like learning such an unfamiliar tool. Still, it’s not as if there isn’t logic behind it because it will work both in a terminal session (where I may have met it for the first time) and a desktop application GUI. The latter is the easier to learn, and the menus list equivalent keyboard shortcuts for many of their entries, too. For a fuller experience though, I can recommend the online manual, and you can buy it in paper form too if you prefer.
One thing that I discovered recently is that external factors can sour the impressions of a piece of software. For instance, I was using a UNIX session where the keyboard mapping weren’t optimal. There’s nothing like unfamiliar behaviour for throwing you off track because you felt your usual habits were being obstructed. For instance, finding that a Backspace key is behaving like a Delete one is such an obstruction. It wasn’t the fault of Emacs, and I have found that using Ctrl+K (C-k in the documentation) to delete whole lines is invaluable.
Apart from keyboard mapping niggles, Emacs has to be respected as a powerful piece of software in its own right. It may not have the syntax highlighting capabilities of some, like gedit or NEdit for instance, but I have a hunch that a spot of Lisp programming would address that need. What you get instead is support for version control systems like RCS or CVS, along with integration with GDB for debugging programs written in a number of languages. Then, there are features like file management, email handling, newsgroup browsing, a calendar and calculator that make you wonder if they tried to turn a text editor into something like an operating system. With Google trying to use Chrome as the basis of one, it almost feels as is Emacs was ahead of its time, though that may have been more due to its needing to work within a UNIX shell in those far-off pre-GUI days. It really is saying something that it has stood the test of time when so much has fallen by the wayside. Like Vi, it looks as if the esteemable piece of software is showing no signs of going away just yet. Maybe it was well-designed in the beginning, and the thing certainly seems more than a text editor with its extras. Well, it has to offer a good reason for making its way into Linux too…
One of the nice things about working with Linux/UNIX is that you can organise your open applications so that they are open in different workspaces or virtual desktops. When I return to working on Windows, having everything open on the same desktop is something that I find less tidy. However, there is an open source application that adds virtual desktops to Windows and very useful it is too.
It is called VirtuaWin and it adds an icon to the taskbar for switching between workspaces when it is running; there might be a bit of tweaking to be done for it to stay visible all of the time though. You can have it as a startup application in the same way that you have your security software and I have been using it smoothly on both Windows XP and Windows 7 running in VirtualBox virtual machines. Insofar as I have seen it, you can have as many workspaces as you want and switching from one to another is achievable using keyboard shortcuts. Using CTRL, ALT and one of the arrow keys does it for me but you can set up your own. All in all, it’s a small download that brings a little sense of Windows desktop computing.