How would I hook into a file that's currently in use by another program, which constantly writes out to it? Let's say, there's a text file with 10 lines. When I start my app it has to detect and read any content from there on everytime the writing program saves its content. Can this be done without a constant check on the filesize/date?
You could monitor the folder for changes using the ReadDirectoryChangesW API.
Keep track of the last position you read to, and when you receive a change notification for that file, read from there to the end of the file (as it currently stands).
An example of how to use the ReadDirectoryChangesW API is here:
Why does ReadDirectoryChangesW omit events?
Kinda similar to this:
Monitor files similar to System Internal's/Microsoft's FileMon/Process Monitor
Related
We have a network drive (ntfs). I want to monitor any kind of changes (like making a file read only or hidden) that are done to files in this drive. I also want to track the name of the user who has done this.
I created a program in C# using FileSystemWatcher to monitor changes. But with this, I could monitor changes only done by me. If some other user is changing it, I am not getting any notifications.
Any solution through which this can be achieved. It's not necessary for me to use C#. I would welcome solutions in any language.
How to know what file was changed (it's name) on Change Event of TJvChangeNotify (JEDI) or TShellChangeNotifier?
Thanks!
Both components use FindFirstChangeNotification to monitor changes. As indicated in its documentation the function does not provide information on what triggered the notification. As such the only possible way to find out what happened using these components is to keep a snapshot of the monitored folder and perform a comparison after a change occurs.
If you decide to use ReadDirectoryChangesW as suggested by FindFirstChangeNotification's documentation, see this answer. Or instead, if you decide to use SHChangeNotifyRegister see this article.
Looking for a little help getting started on a little project i've had in the back of my mind for a while.
I have log file(s) varying in size depending on how often they are cleaned from 50-500MB. I'd like to write a program that will monitor the log file while its actively being written to. when in use it's being changed pretty quickly easily several hundred lines a second or so. Most if not all of the examples i've seen for reading log/text files are simply open and read file contents into a variable which isn't really feasible to do every time the file changes in this situation. I've not settled on a language to write this in but its on a windows box and I can work in .net flavors / java / or php ( heh dont think php will fly to well for this), and can likely muddle through another language if someone has a suggestion for something well built for handling this.
Essentially I believe what I'm looking for would probably be better described to as a high speed way of monitoring a text file for changes and seeing what those changes are. Each line written is relatively small. (less than 300 characters, so its not big data on each line).
EDIT: to change the wording to hopefully better describe what i'm trying to do. Which is write a program to keep an eye on a log file for a trigger then match a following action to that trigger. So my question here is pertaining to file handling inside a programming language.
I greatly appreciate any thoughts/comments.
If it's incremental then you can just read the whole file the first time you start analyzing logs, then you keep the current size as n. Next time you check (maybe a timed action to check last modified date) just skip first n bytes, read all new bytes and update size.
Otherwise you could use tail -f by getting its stdout and using it for your purposes..
The 'keep an eye on a log file' part of what you are describing is what tail does.
If you plan to implement it in Java, you can check this question: Java IO implementation of unix/linux "tail -f" and add your trigger logic to lines read.
I suggest not reinventing the wheel.
Try using the elastic.co
All of these applications are open source and free and are capable of monitoring (together) and trigger actions based on input.
filebeats - will read the log file line by line (supports multiline log messages as well) and will send it across to logstash. There are loads of other shippers you can use.
logstash - will take the log messages, filter them, add tags and send the messages to elasticsearch
elasticsearch - will take the log messages and index them, the store them. It is also capable of running actions based on input
kibana - is a user friendly web interface to query and analyze the data. Or just simply put it up on a dashboard.
Hope this helps.
I am creating one desktop application in which I want to track user activity on the system like opened Microsoft Excel with file name and worked for ... much of time on that..
I want to create on xml file to maintain that log.
Please provide me help on that.
This feels like one of those questions where you have to figure out what is meant by the question itself. Taken at face value, it sounds like you want to monitor how long a user spends in any process running in their session, however it may be that you only really want to know if, and for how long a user spends time in a specific subset of all running processes.
Since I'm not sure which of these is the correct assumption to make, I will address both as best I can.
Regardless of whether you are monitoring one or all processes, you need to know what processes are running when you start up, and you need to be notified when a new process is created. The first of these requirements can be met using the GetProcesses() method of the System.Diagnostics.Process class, the second is a tad more tricky.
One option for checking whether new processes exist is to call GetProcesses after a specified interval (polling) and determine whether the list of processes has changed. While you can do this, it may be very expensive in terms of system resources, especially if done too frequently.
Another option is to look for some mechanism that allows you to register to be notified of the creation of a new process asynchronously, I don't believe such a thing exists within the .NET Framework 2.0 but is likely to exist as part of the Win32 API, unfortunately I cant give you a specific function name because I don't know what it is.
Finally, however you do it, I recommend being as specific as you can about the notifications you choose to subscribe for, the less of them there are, the less resources are used generating and processing them.
Once you know what processes are running and which you are interested in you will need to determine when focus changes to a new process of interest so that you can time how long the user spends actually using the application, for this you can use the GetForegroundWindow function to get the window handle of the currently focused window.
As far as longing to an XML file, you can either use an external library such as long4net as suggested by pranay's answer, or you can build the log file using the XmlTextWriter or XmlDocument classes in the System.Xml namespace
I'm developing a application in Lazarus, that need to check if there is a new version of a XML file on every Form_Create.
How can I do this?
I have used the synapse library in the past to do this kind of processing. Basically include httpsend in your uses clause, and then call httpgetbinary(url,xmlstream) to retrieve a stream containing the resource. I wouldn't do this in the OnCreate though, since it can take some time to pull the resource. Your better served by placing this in another thread that can make a synchronize call back to the form to enable updates, or set an application flag. This is similar to how the Chrome browser displays updates on the about page, a thread is launched when the form is displayed to check to see if there are updates, and when the thread completes it updates the GUI...this allows other tasks to occur (such as a small animation, or the ability for the user to close the dialog).
Synapse is not a visual component library, it is a library of blocking functions that wrap around most of the common internet protocols.
You'll need to read up on FPC Networking, lNet looks especially useful for this task.