TOPIC: FREE AND OPEN-SOURCE SOFTWARE
Creating empty text files and changing file timestamps using Windows Command Prompt & Powershell
17th May 2013Linux and UNIX have the touch command for changing the creation dates and times for files. However, it also creates 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 file1
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 directory1
Note that file1 in the previous example has become directory1 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?
Saving Windows Command Prompt & Powershell command history to a file for later useage
15th May 2013It's remarkable what ideas Linux gives that you wouldn't encounter that clearly in the world of Windows. One of these is output and command line history, so a script can be created. In the Windows world, this would be called a batch file. Linux usefully has the history command, and it does the needful for taking a snapshot like so:
history > ~/commands.sh
All the commands stored in a terminal's command history get stored in the commands.sh in the user's home area. The command for doing the same thing from the Windows command line is not as obvious because it uses the doskey command that is intended for command line macro writing and execution. Usefully, it has a history option that tells it to output all the commands issued in a command line session. Unless, you create a file with them in there, there appears to be no way to store all those commands across sessions, unlike UNIX and Linux. Therefore, a command like the following is a partial solution that is more permanent than using the F7 key on your keyboard:
doskey /history > c:\commands.bat
Windows PowerShell has something similar too, and it even has aliases of history and even h. All PowerShell scripts have file extensions of ps1 and the example below follows that scheme:
get-history > c:\commands.ps1
However, I believe that even PowerShell doesn't carry over command history between sessions, though Microsoft is working on adding this useful functionality. While they could co-opt Cygwin of course, that doesn't seem to be their way of going about things.
Shell swapping in Windows: PowerShell and the legacy command prompt
28th April 2010Until the advent of PowerShell, Windows had been the poor relation when it came to working from the command line when compared with UNIX, Linux and so on. A recent bit of fiddling had me trying to run FTP from the legacy command prompt when I ran into problems with UNC address resolution (it's unsupported by the old technology) and mapping of network drives. It turned out that my error 85 was being caused by an unavailable drive letter that the net use command didn't reveal as being in use. Reassuringly, this wasn't a Vista issue that I couldn't circumvent.
During this spot of debugging, I tried running batch files in PowerShell and discovered that you cannot run them there like you would from the old command prompt. In fact, you need a line like the following:
cmd /c script.bat
In other words, you have to call cmd.exe like perl.exe, wscript.exe and cscript.exe for batch files to execute. If I had time, I might have got to exploring the use ps1 files for setting up PowerShell commandlets, but that is something that needs to wait until another time. What I discovered though is that UNC addressing can be used with PowerShell without the need for drive letter mappings, not a bad development at all. While on the subject of discoveries, I discovered that the following command opens up a command prompt shell from PowerShell without any need to resort to the Start Menu:
cmd /k
Entering the exit command returns you to the PowerShell command line again, and entering cmd /? reveals the available options for the command, so you need never be constrained by your own knowledge or its limitations.
Why I’ll be keeping Windows close to hand for a while to come
2nd December 2007Even though I have moved to Linux, and it has been fulfilling nearly all of my home computing needs, I do and plan to continue to retain access to Windows courtesy of virtualisation technology. Thought keeping current with the world of the ever pervasive Windows is one motivation, there are others. In fact, now that Windows is more of a sideline, I may even get my hands on Vista at some point to take a further in-depth look at it, hopefully without having to suffer the consequences of my curiosity.
Talking of other reasons for hanging onto Windows, listening to music secured by DRM does come to mind. DRM is seen in a negative light by many in the open-source world, so Linux remains unencumbered by the beast. That isn't necessarily a bad thing, and the whole furore about Vista and DRM earlier this year had me wondering about a Linux future. However, I have been known to buy music from iTunes and would like to continue doing so. Though WINE might be one way to achieve this, retaining Windows seems a sounder option. That way, I am saved from having to convert my protected music files into either Ogg Vorbis or FLAC; the latter involves a lossless compression unlike the former, so the files are bigger with the additional quality that an audiophile would seek. MP3 is another option, yet there are those in the Linux world who frown upon anything patented. That makes getting MP3 support an additional task for those of us wanting it.
In my wisdom, I have succumbed to the delights of expensive web development tools like Altova's XMLSpy and Adobe's Dreamweaver. While I have found a way to get Quanta Plus to edit files on the web server directly and code hacking is my main way to improve my websites, I still will be having a bimble into Dreamweaver from time to time. I have yet to see XMLSpy's grid view replicated in the open-source world, so that should remain a key tool in my arsenal. While I haven't been looking too hard at open-source XML editors recently, there remains unexplored functionality in XMLSpy that I should really explore to see if it could be harnessed.
While I have included implicit references to this already, it needs saying that keeping Windows around also allows you to continue using familiar software. For some, this might be Microsoft Office, but OpenOffice and Evolution have usurped this in my case. Photoshop Elements is a better example for me. Digital transfers from scanners and DSLR's will stay in the world of Linux, while virtualisation allows me to process the images in whatever way I want. For now, I might just stick with the familiar before jumping ship to GIMP at some point in the future. With all that is written on Photoshop, having it there for learning new things seems a very sensible idea.
While open-source software can conceivably address every possible, there are bound to be niches that remain outside its reach. I use mapping software from Anquet when planning hillwalking excursions. It seems very much to be a Windows only offering and I have already downloaded a good amount of mapping, so Windows has to stay if I need to use this and the routes that I have plotted out before now. Another piece of software that finds its way into this bracket is my copy of SAS Learning Edition; there are times when a spot of learning at home goes a long way at work.
So, in summary, my reasons for keeping Windows around are as follows:
- Learning new things about the thing, since I am unlikely to escape its influence in the world of work
- Using iTunes to download new music and to continue to listen to what I have already
- Using and learning about industry standard web development tools like Dreamweaver and XMLSpy
- Easing the transition, by continuing to use Photoshop Elements, for example
- Using niche software like Anquet mapping
Though I suppose that many will relate to the above, Linux still has plenty to take over some of the above. In time, DRM may disappear from the music scene and not before time; accountants and shareholders may need to learn to trust customers. NVu and Quanta Plus could yet usurp Dreamweaver, and there may be an open-source alternative to XMLSpy like there is for so many other areas. The Photoshop versus GIMP choice will continue to prevent itself and all that is written about the former makes it seem silly to throw it away, however good the latter is. Even with changing over Linux equivalents of applications fulfilling standard needs, it still leaves niche applications like hillwalking mapping and that, together with the need to know what Windows might offer in the enterprise space, could be the enduring reasons for keeping it near to hand. That said, I can now go through whole days without firing up a Windows VM, a big change from how it was a few months ago. Still, I suppose that it's all too easy to stick with using one operating system at a time, which is Linux for me these days.
Filename autocompletion on the command line
19th October 2007The Windows 2000 command line feels an austere primitive when compared with the wonders of the UNIX/Linux equivalent. Windows XP feels a little better, and PowerShell is another animal altogether. With the latter pair, you do get file or folder autocompletion upon hitting the TAB key. What I didn't realise until recently was that continued tabbed cycled through the possibilities; I was hitting it once and retyping when I got the wrong folder or file. I stand corrected. With the shell in Linux/UNIX, you can get a listing of possibilities when you hit TAB for the second time and the first time only gives you completion as far as it can go with certainty; you'll never get to the wrong place, though you may not get anywhere at all. This works for bash, but not ksh88 as far as I can see. It's interesting how you can take two different approaches to reach the same end.