[VB.NET] Deleting string from text file

[Puggsley]

I need to search through a .txt file and remove a specific string. Anything i've found so far deletes a specific line number, but the string could appear on any line.

Any help would be greatly appriciated as i've been at this for a long time now!

[James Rose]

  Puggsley said:

I need to search through a .txt file and remove a specific string. Anything i've found so far deletes a specific line number, but the string could appear on any line.

Ok, this answer will work, but I'm sure there are less expensive ways to achive the desired result. That said... Load the entire file into a string (oh my!) and then do a String.Replace("OLD VALUE", "") and then save the string to the file.

If the file is small, this is not a big deal, if the file is large it can take a serious chunk of memory.

If I think of something else I'll post back.

[Puggsley]

Thanks for the prompt reply!

Thats the best solution i could come up with as well. As for the file size, there is about 10 files, varying from 20kb to 5mb so it could be a problem. Time and memory isn't too much of an issue and if it becomes one then it is something to look at in the future, but right now its more important to get something working

How much of a problem do you think it will be?

[James Rose]

I think the 5mb file is a LITTLE bit of an issue, but since these days (as opposed to 1995) memory is cheap and plentiful it's not something I would freak about.

If you write your code well, when you find a better solution, you'll be able to change that small chunk of code and get better performance. (hack? oh a little)

If it was me, and I was out of time, I'd go with the original idea and then at a later date do the performance gain. I've done tech work for 20 years and dev for 15. *I* find it most important to get the job done, over having it done well. Done well is nice, but not if it's NOT done. (read that sentence carefully)

[MECL]

Would it be possible to read the file just one line at a time? This way only one line will have to be in memory. There may be a way to loop this method until the end of file has been reached. Just search through each line one at a time for the string to remove it. After the line has been analyzed, unload it and load the next line.

I'm not sure how you would go about coding this, but perhaps the idea will spark something. :)

[James Rose]

The problem with the "line by line" is that VB opens access to the file and will allocate a chunk of memory near the size of the file in either case. This is a concern and I'm sure there is a better solution that I have stated above... at the moment I don't have one. (sorry)

EDIT:

I thought I'd make a comment here: Besides the coding issues another point of development work is to know which goals to reach for... I had a friend back in San Francisco that spent a month creating a reporting engine in VB. Considering his fee and the abilities of VB the time would have been much better spent purchasing Crystal Reports or some other engine and having a large number of reports created by the end of that first month. (of course there are arguments for creating the engine, but in this case it was a serious waste of the client's cash)

SOMETIMES getting something done quickly vs writing tight, memory and CPU light code is better. It's a case by case issue based on the information at hand and the time alotted.

Just food for thought.

Peace,

James Rose

New York City

Edited March 10, 2008 by jameswjrose

[Puggsley]

OK, so i took the plunge and went with the original suggestion but am having real difficulties getting it to work

To make sure its nothing else in the program i created a new project and put the following code on the form load event and created a text file with the contents "Hello World" in the output folder

Dim FileContents as String
Dim objReader as System.IO.StreamReader
objReader - New StreamReader(Environment.CurrentDirectory & "\test.txt")
FileContents = objReader.ReadToEnd
objReader.Close
FileContents.Replace("Hello", "")
Dim objWriter as System.IO.StreamWriter
objWriter = New StreamWriter(Environment.CurrentDirectory & "\test.txt")
objWriter.Write(FileContents)
objWriter.Close

From watching in explorer the program seems to zero byte the file and then write exactly the same contents back again.

Any ideas would be greatly appreciated!

[+Nik Louch Subscriber²]

FileContents = FileContents.Replace("Hello", "")

[Puggsley]

Wow! I think its time for a break

I can't believe I missed that (Hangs head in shame then goes to find food)

[+Nik Louch Subscriber²]

That means it is time for a break. We all make this mistakes when we're blinded by our own code!