Is there a way to determine programatically if a particular directory is actually remotely mounted? Can this be done with Java, and if not can it be done with native C code over JNI?
Since this is Java it could be running under Linux or Windows or Mac, so a proper solution needs to address all these platforms. (Again if its multiple separate solutions with C over JNI thats ok). And there may be different cases like with NFS or samba or anything else.
Thanks.
for Linux, and possibly Macintosh, you can use system library through JNI.
The relevant system call is getmntent, described here.
There is a field in mntent you can use to check to see if mount point is from device or a server, mnt_fsname, in a similar field you can get filesystem type, `mnt_type"
For Linux, you can parse /etc/mtab to find the filesystem type (nfs, smb, etc.) and match it against known network filesystem types in your program.
EDIT: column 2 is what you want in /etc/mtab
I need that as well and might end up implementing it using this command:
df -k
That works under Linux, Mac OS and Solaris.
Maybe this is something else that will be added to JDK 7 since they're also going to support symlinks.
Related
i am working on a method to import files which are stored on an usb device to my database.
I already done it for Mac and Windows, but I don't know how to get the path to the usb device when the application is used under Linux/Ubuntu with java.
Is there a way to find the path?
I don't think there is any way that is guaranteed to work on all Linux systems. There are a few approaches I have used, with varying degrees of success.
A method that requires no external utilities is to enumerate and parse the pseudo-files in /dev/disk, /proc/mounts, and /sys/bus/usb, and build a representation of the USB devices that hold storage. There might be more than one, so you might still have to make some guesses, or offer users a choice. This is a pretty tedious method, but I think it is the most general. You can just look at /media, /run/media, as somebody else suggested, but this only works on some Linux installations, and only if that form of auto-mounting is enabled.
A less tedious approach is to invoke the utility udisksctl from your program. I think this utility exists for almost all Linux variants, but it isn't always installed by default. The output of the utility has to be parsed, but it's less hassle that working directly with the kernel psedofiles.
To get a list of disk devices, execute udisksctl status. This will tell you the model name, which will often include the text "USB", and the block device (e.g., /dev/sdb). Then you can execute udisksctl info -b /dev/sdb and look for the line that begins "MountPoints". If the device is not mount you could, if you wished, force it by executing udisksctl mount.... There's a heap of other useful stuff that udisksctl can do -- see its man page.
In Java you can use Runtime.exec() to run udisksctl, but it's probably friendlier to users to check that it is installed first, by check for the existence of /usr/bin/udisksctl.
The easiest way I found is using the Volumes directory.
/Volumes/NAME_OF_USB_DRIVE/file.whatever
I need to detect OS name & version in Java. That I can do by
String os_name = System.getProperty("os.name", "");
String os_version = System.getProperty("os.version", "");
but the problem is that this is not reliable. Sometimes it returns incorrect information, and I can't detect all operating systems, except the most popular Windows, MacOS, Linux etc, and this even provides wrong information in the case of 64 bit operating systems. I need to detect any OS with any kind of specification. I am unable to find the right solution for this.
Maybe I can do this with JavaScript? If it's impossible in Java then please tell me how to do it with JavaScript.
Any input or suggestions highly appreciated.
Thanks in advance.
Best regards,
**Nilanjan Chakraborty
In Java there are some common bugs while guessing the operating system:
http://bugs.sun.com/view_bug.do?bug_id=6819886
Maybe in newer versions of Java, they are solved.
In Javascript you can use navigator.appVersion:
// This script sets OSName variable as follows:
// "Windows" for all versions of Windows
// "MacOS" for all versions of Macintosh OS
// "Linux" for all versions of Linux
// "UNIX" for all other UNIX flavors
// "Unknown OS" indicates failure to detect the OS
var OSName="Unknown OS";
if (navigator.appVersion.indexOf("Win")!=-1) OSName="Windows";
if (navigator.appVersion.indexOf("Mac")!=-1) OSName="MacOS";
if (navigator.appVersion.indexOf("X11")!=-1) OSName="UNIX";
if (navigator.appVersion.indexOf("Linux")!=-1) OSName="Linux";
document.write('Your OS: '+OSName);
All the browser's I'm familiar with report the OS from the navigator object (javascript)-
alert(navigator.platform)//returns string- eg'Win64'
There are not too much ways to detect this. Most probably it will work correctly 99% of the time.
However if you are looking for another method, you can consider checking some magic file paths. i.e:
if /etc or /proc folders exists, it is Linux
if C:\Windows\ exists, it is Windows.
etc.
However they won't be again reliable since /etc /proc may also exist in Mac.
If you want to find exact name of the OS, you can look at /etc/issue file in Unix-Linux-Mac and you can use "os.name" (which you claim that it is inaccurate) or WMI (windows management instrument) to retrieve OS name+version.
I would like to know whether or not Java is installed and where (path).
Perhaps it sounds strange, but my aim is to let BOINC (coded in C++) check the Java installation and then start my Java app. But therefore I need to know if BOINC can start Java natively, or if I have to also send the JRE and then start my app with this not installed JRE.
So is there a way to check the installation first?
thank you in advance!
Andreas
I would start with checking of java's environment variables,
also, in linux/unix distros you can try the "which java" command,
and in windows operating systems you can check the registry.
if all else fails, you can also try to find the java binary but I think this isn't practical (time consuming).
I have a Java application which requires certain software (one of them being Perl) before it can be run. What I used to do to detect for Perl is:
Runtime.getRuntime().exec("perl Test.pl");
and if there was an IOException declare that there was no Perl.
However, one of my users complained that the app kept failing because he had not placed Perl in his path varible. So this is why I'm asking: Is there any cross-operating system way to detect whether Perl (or any other software) is installed on the user's system and the path to the program?
These kind of questions seem to be popping out every now and then and the answer (almost) always is no. Most general reason for the negative answer is that Java is run in a homogenous Virtual Machine environment which is by design the same on all platforms; Those operations you can't abstract away/do reliably on at least the most supported platforms just can't be done easily. Detecting external events in the OS in general such as which non-Java applications are also run/installed falls into that "not easy to do" category.
Certainly there could be need/market for JNI libraries for the purpose but those steer heavily from the cross-platform requirement these questions always seem to want to and that's why the short answer is "no". As far as I can see, what you're doing currently is the cleanest way to detect Perl unless you're willing to include perljvm or similar in your project.
If the user is not willing to either
Install perl in an agreed upon location
Indicate where perl has been installed by storing it's location in an environment variable, config file, windows registry, etc.
then it seems you're only option is to search the entire disk for an executable named 'Perl'. Obviously this could take a very long time, but if you store the location somewhere, at least you should only need to search for it once
I don't know your target audience (users), but upon failure you could prompt the user to enter the path (a FileChooserDialog) and then store this path for future usage (if the exception is not thrown again). I did that some time ago, luckily I had users that were SysAdmins, so it was OK for them to provide that info when the error happened the first time (I also documented how to update or change these values in a properties file).
Other option as mentioned by Don, is to install the required software as relative to your installation, that's a more common option.
Getting windows native information using java SDK is not possible without support of external APIs. Instead of using external APIs (which is mostly LGPL licensed and not completely open), we can use the shell commands to get the same.
Step 1 - Checking if (perl) an application is installed
For checking if an application is installed, use ProcessBuilder or Runtime.exec to run one of the following PowerShell command,
Get-ItemProperty HKLM:\Software\Microsoft\Windows\CurrentVersion\Uninstall* | Select-Object DisplayName | where {$_.DisplayName -match "perl"}
Replace "perl" with your choice of software and stream the output of these and process it.
If PERL (for above question), follow below 2 steps to set path and run perl script from java
Step 2 - If available, set it to Environment Path using java code.
Step 3 - Run your perl script.
In my Scala (runs on top of Java) Application I would like to get a list of all drives that contain DVD media, e.g. something like this:
/dev/scd0 Star Trek DS9 DVD1
/dev/scd0 The 4400 DVD1
Not sure if it's possible to get the name of the disc, but the path is the important thing for me anyway.
I would prefer a pure Java / Scala solution (using file.io stuff). If that's not possible, accessing the right Linux files is fine, too (like /proc/something).
Thanks in advance!
I think you're out of luck with java.io.* but if you don't mind making calls out to Linux commands, you could assemble the data by:
Calling "mount" and capturing the first column of output.
Calling "volname" on each value you captured from step 1.
According to the man page for volname, it only returns data for ISO-9660 filesystems (e.g. DVDs), so any device path that returns empty can be ignored.
There is one (untested) possibility to get your drives with pure Java code. At least on Windows.
Its a little bit hacky and doesn't work under linux (because linux gets not as much integration love from sun I believe).
import javax.swing._
import javax.swing.filechooser._
val chooser = new JFileChooser()
val view = chooser.getFileSystemView()
The FileSystemView clas provides a few features such as asking the possible roots if they
are a drive (isDrive()). Swing uses this to present the file chooser with the right icons to
you so it should work under windows because IIRC it shows the correct symbols there. Under
Linux it unfortunately does only show the "/" root.
One of the reasons this doesn't work under linux could be, that the linux developers constantly change their preferred way of presenting such information to the user space. at the moment it is IIRC hal and dbus. Maybe SUN didn't want to publish a new java version each time this changes.
If pure java doesn't cut it maybe you could use a little bit of jni (which is not so hard to use anymore if you're using tools like JNA or such) to access the linux apis directly. I haven't done that but could try if you're interested.