Adventures & experiences in contemporary technology
There are times when blogs cease to exist and the only place to find the content is on the Wayback Machine. Even then, it is in danger of being lost completely. One such example is the subject of this post.
Though this website makes use of the facilities of Cloudflare for various functions that include the blocking of image hotlinking, the same outcome can be achieved using .htaccess files on Apache web servers. It may work on Nginx to a point too but there are other configuration files that ought to be updated instead of using a .htaccess when some frown upon the approach. In any case, the lines that need adding to .htaccess are listed below though the web address needs to include your own domain in place of the dummy example provided:
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)?yourdomain.com(/)?.*$ [NC]
RewriteRule .*\.(gif|jpe?g|png|bmp)$ [F,NC]
The first line turns on the mod_rewrite engine and you may have that done anyway. Of course, the module needs enabling in your Apache configuration for this to work and you have to be allowed to perform the required action as well. This means changing the Apache configuration files. The next pair of lines look at the HTTP referer strings and the third one only allows images to be served from your own web domain and not others. To add more, you need to copy the third line and change the web address accordingly. Any new lines need to precede the last line that defines the file extensions that are to be blocked to other web addresses.
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)?yourdomain.com(/)?.*$ [NC]
RewriteRule \.(gif|jpe?g|png|bmp)$ /images/image.gif [L,NC]
Another variant of the previous code involves changing the last line to display a default image showing others what is happening. That may not reduce the bandwidth usage as much as complete blocking but it may be useful for telling others what is happening.
Like Fedora, Manjaro also installs a package for VirtualBox Guest Additions when you install the Linux distro in a VirtualBox virtual machine. However, it does have certain expectations when doing this. On many systems and my own is one of these, Linux guests are forced to use the VMSVGA virtual graphics controller while Windows guests are allowed to use the VBoxSVGA one. It is the latter that Manjaro expects so you get a message like the following appearing when the desktop environment has loaded:
Windows Resizing
Set your VirtualBox Graphics Controller to enable windows resizing
After ensuring that gcc, make, perl and kernel headers are installed, I usually install VirtualBox Guest Additions myself from the included ISO image and so I did the same with Manjaro. Doing that and restarting the virtual machine got me extra functionality like screen resizing and being able to copy and paste between the VM and elsewhere after choosing the Bidirectional setting in the menus under Devices > Shared Clipboard.
That still left an unwanted message popping up on startup. To get rid of that, I just needed to remove /etc/xdg/autostart/mhwd-vmsvga-alert.desktop. It can be deleted but I just moved it somewhere else and a restart proved that the message was gone as needed. Now everything is working as I wanted.
My usual method for copying a directory tree without any of the files in there involves the use of the Windows commands line XCOPY and the command takes the following form:
xcopy /t /e <source> <destination>
The /t switch tells XCOPY to copy only the directory structure while the /e one tells it to include empty directories too. Substituting /s for /e would ensure that only non-empty directories are copied. <source> and <destination> are the directory paths that you want to use and need to be enclosed in quotes if you have a space in a directory name.
There is one drawback to this approach that I have discovered. When you have long directory paths, messages about there being insufficient memory are issued and the command fails. The limitation has nothing to do with the machine that you are using but is a limitation of XCOPY itself.
After discovering that, I got to checking if ROBOCOPY can do the same thing without the same file path length limitation because I did not have the liberty of shortening folder names to get the whole path within the length expected by XCOPY. The following is the form of the command that I found did what I needed:
robocopy <source> <destination> /e /xf *.* /r:0 /w:0 /fft
Again, <source> and <destination> are the directory paths that you want to use and need to be enclosed in quotes if you have a space in a directory name. The /e switch copies all subdirectories and not just non-empty ones. Then, the xf *.* portion excludes all files from the copying process. The remaining options are added to help with getting around access issues and to try copy only those directories that do not exist in the destination location. The /ftt switch was added to address the latter by causing ROBOCOPY to assume FAT file times. To get around the folder permission delays, the /r:0 switch was added to stop any operation being retried with /w:0 setting wait times to 0 seconds. All this was enough to achieve what I wanted and I am keeping it on file for my future reference as well as sharing it with you.
Recently, a timestamp got changed on an otherwise unaltered file on me and I needed to change it back. Luckily, I found an answer on the web that used PowerShell to do what I needed and I am recording it here for future reference. The possible commands are below:
$(Get-Item temp.txt).creationtime=$(Get-Date "27/10/2014 04:20 pm")
$(Get-Item temp.txt).lastwritetime=$(Get-Date "27/10/2014 04:20 pm")
$(Get-Item temp.txt).lastaccesstime=$(Get-Date "27/10/2014 04:20 pm")
The first of these did not interest me since I wanted to leave the file creation date as it was. The last write and access times were another matter because these needed altering. The Get-Item commandlet brings up the file, so its properties can be set. Here, these include creationtime, lastwritetime and lastaccesstime. The Get-Date commandlet reads in the provided date and time for use in the timestamp assignment. While PowerShell itself is case-insensitive, I have opted to show the camel case that is produced when you are tabbing through command options for the sake of clarity.
The Get-Item and Get-Date have aliases of gi and gd, respectively and the Get-Alias commandlet will show you a full list while Get-Command (gcm) gives you a list of commandlets. Issuing the following gets you a formatted list that is sent to a text file:
gcm | Format-List > temp2.txt
There is some online help but it is not quite as helpful as it ought to be so I have popped over to Microsoft Learn whenever I needed extra enlightenment. Here is a command that pops the full thing into a text file:
Get-Help Format-List -full > temp3.txt
In fact, getting a book might be the best way to find your way around PowerShell because of all its commandlets and available objects.
For now, other commands that I have found useful include the following:
Get-Service | Format-List
New-Item -Name test.txt -ItemType "file"
The first of these gets you a list of services while the second creates a new blank text file for you and it can create new folders for you too. Other useful commandlets are below:
Get-Location (gl)
Set-Location (sl)
Copy-Item
Remove-Item
Move-Item
Rename-Item
The first of the above is like the cwd or pwd commands that you may have seen elsewhere in that the current directory location is given. Then, the second will change your directory location for you. After that, there are commandlets for copying, deleting, moving and renaming files. These also have aliases so users of the legacy Windows command line or a UNIX or Linux shell can use something that is familiar to them.
Little fixes like the one with which I started this piece are all very good to know but it is in scripting that PowerShell really is said to show its uses. Having seen the usefulness of such things in the world on Linux and UNIX, I cannot disagree with that and PowerShell has its own IDE too. That may be just as well given how much there is to learn. That especially is the case when you might need to issue the following command in a PowerShell session opened using the Run as Administrator option just to get the execution as you need it:
Set-ExecutionPolicy RemoteSigned
Issuing Get-ExecutionPolicy will show you if this is needed when the response is: Restricted. A response of RemoteSigned shows you that all is in order, though you need to check that any script you then run has no nasty payload in there, which is why execution is restrictive in the first place. This sort of thing is yet another lesson to be learnt with PowerShell.
It was an article in a magazine that revealed these legal BitTorrent download sites to me, so I thought that I’d keep them on file for future reference while also sharing them with others who might need them. As far as I am aware, they are all legal in that no copyrighted material is on there. If that changes, I am happy to know and make amendments as needed.
My own interest in torrents arises from their being a convenient way to download installation disk images for Linux distributions, and at least one of the entries is devoted to just that. However, the distribution also lends itself to movies along with music and books, so that is reflected below too. With regard to downloading actual multimedia content, there is so much illegal downloading that a list like this is needed and has blackened the reputation of BitTorrent too because it only ever was conceived as a means for distributing large files in a peer-to-peer manner without the use of a single server. Of course, any use can be found for a technology, and it never has to be legal or morally acceptable either.
With a growing collection of photographic images, I often find myself making backups of files using copy commands and the data volumes are such that I don’t want to keep copying the same files over and over again so incremental file transfers are what I need. So commands like the following often get issued from a Linux command line:
cp -pruv [source] [destination]
Because this is in Linux, it the bash shell that I use so the switches may not apply to others like ssh, fish or ksh. For my case, p preserves file properties such as its time and date and the cp command does not do this always so it needs adding. The r switch is useful because the copy then in recursive so only a directory needs to specified as the source and the destination needs to be one level up from a folder with the same name there so as to avoid file duplication. It is the u switch that makes the file copy incremental and the v one issues messages to the shell that show how the copying is going. Seeing a file name issued by the latter does tell you how much more needs to be copied and that the files are going where they should.
What inspired this post though is my need to do the same in a Windows session and issuing xcopy commands will achieve the same end. Here are two that will do the needful:
xcopy [source] [destination] /d /s
xcopy [source] [destination] /d /e
In both cases, it is the d switch that ensures that the copy is incremental and you can add a date too, with a colon between it and the /d, if you see fit. The s switch copies only directories that contain files while the e one copies even empty directories. Using the d switch without either of those did not trigger any copying action when I tried so I reckon that you cannot do without either of them. By default, both of these commands issue output to the command line so you can keep an eye on what is happening and this especially is useful when ensuring that files are going to the right destination because the behaviour differs from that of the bash shell in Linux.
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?
Copy and pasting between Windows programs can cause unwanted formatting to be carried over. Copying text from Internet Explorer into Outlook is one example of this that I see a lot and Word to Word does it too. A trick that I picked up for avoiding this copying of formatting comes from a while back: copying into Notepad and pasting from there. Doing the copy/paste shuffle in that way strips off the formatting baggage and alllows the default formatting for the particular destination to be applied. There may be other and slicker ways to do this but what I have described works for me.
SAS uses its transport file format to port files between operating and, where the need arises, different software versions. As with a lot of things, there is more than one method to create these transport files: PROC CPORT/CIMPORT and PROC COPY with the XPORT engine. The former method is for within version transfer of SAS files between different operating systems (UNIX to Windows, for instance) and the latter is for cross-version transfer (SAS9 to SAS 8, for example. SAS Institute have a page devoted to this subject which may share more details.