Overwriting a part of a text file?

Hi, i am writing an application where i can set markers on a waveform graph,
now i want to write the values of the markers in a text-based file
(spreadsheet) I make one file with several markers, but it happens that i
want to overwrite a part of the text file, where a marker is, does anyone
knows how to overwrite a part of a text file, with a VI with inputs of an
offset and a length?
Best regards,
Thijs

The "Write File" function has an offset input. The lenght written is the length of the data on input. First you open the file giving its path to "Open File", you write data at offset and "Close File". The previous content of the file at offset is overwritten.
LabVIEW, C'est LabVIEW

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Sorry, im new to Labview.
My situation is
this.
I can store the name and the result and i have the index.
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I
give you an example.
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i'll attach my program i have done soon.

you got the wrong idea.
i do not want to replace the file to a new file.
what i want was to edit the exsiting file if the same name appear twice.
Example:
in my text file i have already had the name of example Tom and result 80
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i wan was to overwrite the result.
my project was similar to this here is my attachment of my project
Attachments:
LOCATOR.vi ‏19 KB
TESTCAR.txt ‏1 KB

Read multiple text files and sort them

I am trying to read multiple text files and store the data from the file in vector.
but for days. I am with no luck. anyone can help me out with it? any idea of how to sort them will be appreciated.
Below is part of the code I implemented.
public class packet {
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    private int user_id;
    private int packet_id;
    private int packet_seqno;
    private int packet_size;
    public packet(int timestamp0,int user_id0, int packet_id0,int packet_seqno0, int packet_size0)
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0 1 1 1 512
1 2 1 2 512
2 3 1 3 512
3 4 1 4 512
4 5 1 5 512
5 6 1 6 512
6 7 1 7 512
7 8 1 8 512
8 9 1 9 512
9 10 1 10 512
10 1 2 11 512
11 2 2 12 512
12 3 2 13 512
13 4 2 14 512
14 5 2 15 512
15 6 2 16 512
16 7 2 17 512

Here's a standard idiom for object-list-sorting:
/* cnleafdata.txt *********************************************
0 1 1 1 512
1 2 1 2 512
2 3 1 3 512
3 4 1 4 512
4 5 1 5 512
5 6 1 6 512
6 7 1 7 512
7 8 1 8 512
8 9 1 9 512
9 10 1 10 512
10 1 2 11 512
11 2 2 12 512
12 3 2 13 512
13 4 2 14 512
14 5 2 15 512
15 6 2 16 512
16 7 2 17 512
import java.util.*;
import java.io.*;
public class Packet implements Comparable<Packet>{
private int timeStamp;
private int userId;
private int packetId;
private int packetSeqno;
private int packetSize;
public Packet(int timeStamp0, int userId0, int packetId0,
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    userId = userId0;
    packetId = packetId0;
    packetSeqno = packetSeqno0;
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public Packet(String timeStamp0, String userId0, String packetId0,
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public Packet(String[] a){
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public void setTime(int aTimeStamp){
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public void setUserId(int aUserId){
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public void setPacketId(int aPacketId){
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public void setPacketSeqno(int aPacketSeqno){
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public void setPacketSize(int aPacketSize){
    packetSize = aPacketSize;
public int getUserId(){
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public String toString(){
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("%2d %2d %2d %2d %4d", timeStamp, userId, packetId, packetSeqno, packetSize);
public int compareTo(Packet otherPacket){
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/* main for test */
public static void main(String[] args){
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just one more question...
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the current code i now have is:
package Assignment1;
import java.util.Scanner;
import java.io.*;
class trialanderror002 {
public static void main(String args[]){
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FileOutputStream out;
PrintStream p;
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Message Edited by Chris_G. on 09-28-2009 11:50 AM
Chris_G
Sr Test Engineer
Medtronic, Inc.

Avoid overwriting text file.

i'm using a rather simple code to write stuff stored in an array to a text file. the only problem is every time i write new stuff to the text file it overwrites the previous file i had how do i stop this from happening.
heres the code:-
public void WriteToFile(){
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               fout3.close();
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Your code can be compressed ...
public void WriteToFile(){
// Stream to write file
final String[] NAMES = {
"ItemName.txt",
"ItemQuantitiy.txt",
"MaxQuantity.txt",
"MinQuantity.txt",
"Charges.txt"
PrintStream[] outs = new PrintStream[5];
try
for (int i = 0;i < outs.length;i++) {
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for (int i = 0;i < itemNo;i++) {
outs[0].println(Item[i]);
outs[1].println(Quantity[i]);
outs[2].println(max[i]);
outs[3].println(min[i]);
outs[4].println(charges[i]);
catch (IOException ex) {
// Error handling here
finally {
// Close all streams here

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CA Forum: Publishing
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Hi Ron,
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Overwriting Text Files?

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Implementation notes: I basically, use a BufferedWriter chained to a FileWriter ... then I close it when Im finished.
BufferedWriter bw = new BufferedWriter(new FileWriter(myFileName));
bw.write("stuff");
bw.newLine();
bw.flush();
bw.close();

...but do I need to be concerned about the old file?No.
...like causing fragments or whatever?Yes, it probably will. No way around it.

Partial Overwrite for text file

I am trying to figure out how to overwrite a single line in a text file for an appointment program I am making. I am having a difficult time with this because I can't figure out how to overwrite a single line. If I could solve this, I could get my delete button (it's GUI) working and my edit button working. Thanks in advance!
-Vegunks

The short answer is that "overwriting" in a text file is problematic, and for a couple reasons:
1. Often you want to replace 50 characters with 70 characters or 30 characters and you can't make a file simply grow or shrink like that.
2. Your text encoding may have some surprises in store for you. Common encodings like UTF-8 can encode a single character as 1, 2 or three bytes depending on its value, so even if you think you are replacing 50 characters with 50 characters, you may be replacing 80 bytes with 84 bytes.
The solution is to rewrite the entire file. More precisely:
1. create a new file and write to it.
2. delete the old file.
3. rename the new file to take the place of the old file.
edit: too slow!

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When you create the CFile/CNiFile object to write to the file, use the CFile::modeNoTruncate flag to indicate that you want to open the file as an existing file and that you don't want the file to be truncated to 0 length. For more information, see documentation for the CFile flags.
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Replace/cut part of words from a text file.

Hello Hello everyone, I have a quick question. I have my text file that contains also words like ... let's say abc1, abc2 and so on, and I need to cut the c from the word, I need ab1, ab2.
Here is what I have started:
import java.util.*;
import java.io.*;
public class test
        Vector<String> x = new Vector<String>();
public mergefiles() throws IOException
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private void readAdd(String name) throws IOException
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               StringTokenizer st=new StringTokenizer(between," \n");
private void write(String name) throws IOException
        BufferedWriter writer = new BufferedWriter(new FileWriter(name));
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public static void main(String[] args) throws IOException
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Thank you!

I have tried in readAdd method something like:
int posX=all.indexOf("X"); // x being like first word of the text file
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for(int i=0;i<word.length;i++)
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Thanks

How to overwrite the header part of a wave file?????

I need to overwirte the header part of a wave file. Any one has ideas or similar experiences?
basically, I want to continousely save wave data from a sound card. At the end of my program, I need to write the data size of the final wave file to the header part of the wave file.
Is there a function to replace the content of a file? Thanks

I assume that what you want to do is add documentation into the header of the wav file such as the media type, location, equipment used .....
Some one may have written some routines to do this in Labview, unfortunately all the ones I have are written in Visual Basic, quite a long time ago.
Here are some pointers in the event that no one has any Labview stuff, we could even knock a few togther, if its not been done.
The WAV file falls into a cateory of Windows files known as RIFF format files, in fact you will see this written into the file header almost at the very front.
I quote here from the Microsoft Technet Article:-
See here for a nice picture and here for full details, although for the header structure I prefer here.
"The basic building block of a RIFF file is a chunk. A chunk is
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A doubleword value specifying the size of the data member in the chunk
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There are standard fourcc codes that exist to hold various specific types of information and if one of these is not suitable you can create your own, there is (well was) even a way to regiser your own special type with Microsoft!!
There are a couple of ways of doing the job (assuming some kind sole does not donate a VI library).
1) Handle all the file i/o yourself by reading in the file and then insert the appropriate headers and rewrite the file out again.
Involved, but cross platform.
2) Muck about with Windows 'mmio' librarys (mmioCreateChunk).
Platform specific but possibly more reliable???
If you select option 1, then what you have to do is read in the appropriate chunk sizes(lengths) contained in the header, insert your appropriate FOURCC code, size(length) and data then adjust the affected 'chunk' size indicators to put all the various size indicators in the correct place, simple ehhh
If you select option 2, this requires linking to the appropriate DLL, it always my last resort to avoid DLL hell and portability issues.
As an example I wrote my own Turbo Pascal and later Visual Basic handlers which allowed attachment of lots of information from a form, and then created a special media format for the data to allow storing native measured data. These files are still recognised by WAV file readers today such as Media Player 10. Of course the data format is not understood because the encoding type was special, but that's the point.
One final point, there was a tool which read in a WAV file displaying all available headers, with C source (Windows 3.X) supplied in the MSDN toolkit. There are probalby other tools available by now, as a last resort If you decide to have a go I can send you my VB alpha version which reads all standard headers, it might write out a few as well (it was a very long time ago).
Good luck.
Message Edité par Conseils le 12-10-2005 04:09 PM

EDITING TEXT FILE

anyone here know how to edit a text file
i can open the file and i try println it adds to the already content of the file
i was thinking of EDITING THE FILE
i mean changing some parts of the files
example i could always change line #2 if it contains data about AGE
somehing like that

i was thinking of EDITING THE FILE
i mean changing some parts of the files
example i could always change line #2 if it contains
data about AGE
somehing like thatThe easiest way is to read the whole file, line by line, and store the lines in a String array. Then change the lines in the array. Finally, overwrite the file with the lines in the array.
Unfortunately, there is a slight problem with doing that. Suppose you write the first line to your file. That will delete everything in the file. But then suppose your program crashes. Poof! You will lose all your data except the one line you wrote to the file.
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Overwriting a part of a text file?

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