I have a binary file to which I want to append a chunk of data at the end of the file, how can I achieve this using C# and .net? Also is there anything to consider when writing to the end of a binary file? Thanks a lot for your help.
private static void AppendData(string filename, int intData, string stringData, byte[] lotsOfData)
{
using (var fileStream = new FileStream(filename, FileMode.Append, FileAccess.Write, FileShare.None))
using (var bw = new BinaryWriter(fileStream))
{
bw.Write(intData);
bw.Write(stringData);
bw.Write(lotsOfData);
}
}
You should be able to do this via the Stream:
using (FileStream data = new FileStream(path, FileMode.Append))
{
data.Write(...);
}
As for considerations - the main one would be: does the underlying data format support append? Many don't, unless it is your own raw data, or text etc. A well-formed xml document doesn't support append (without considering the final end-element), for example. Nor will something like a Word document. Some do, however. So; is your data OK with this...
Using StreamWriter and referencing DotNetPerls, make sure to add the True boolean to the StreamWriter constructor, if otherwise left blank, it'll overwrite as usual:
using System.IO;
class Program
{
static void Main()
{
// 1: Write single line to new file
using (StreamWriter writer = new StreamWriter("C:\\log.txt", true))
{
writer.WriteLine("Important data line 1");
}
// 2: Append line to the file
using (StreamWriter writer = new StreamWriter("C:\\log.txt", true))
{
writer.WriteLine("Line 2");
}
}
}
Output
(File "log.txt" contains these lines.)
Important data line 1
Line 2
This is the solution that I was actually looking for when I got here from Google, although it wasn't a binary file though, hope it helps someone else.
Related
I was wondering if someone can help me solve a issue I have run into while playing with FileStreams. I have been trying to send an integer, 50, to a FileStream and write its value onto a File. However, it writes 2 to the file instead of 50. I know the ASCII representation of 50 is 2, so am not sure if this is part of the issue. If anyone has any pointers, I'd really appreciate it!
Here is my relevant code:
From the main function:
string testMessage = "Testing writing some arbitrary string to a streama";
int tmL = testMessage.Length;
byte bb = Convert.ToByte(tmL);
SendByteStrem(bb);
And here is my streaming function:
public static void SendByteStrem(byte c){
using (Stream ioStream = new FileStream(#"C:\Users\db0201\Desktop\stream.txt", FileMode.OpenOrCreate)){
ioStream.WriteByte(c);
}
}
As you haven't explicitly stated your goal, i will answer the question for what it is.
The easiest way to write to a file would be to use File.WriteAllText which essentially opens a StreamWriter (which in-turn is open a FileStream) and calls Write
Creates a new file, write the contents to the file, and then closes
the file. If the target file already exists, it is overwritten.
File.WriteAllText(fileName, "50")
or
var myInt = 50;
File.WriteAllText(fileName, myInt.ToString())
If you wanted to use the StreaWriter exclusively
using (varwriter = new StreamWriter(fileName))
writer.Write(myInt.ToString());
If you wanted more configuration over the underlying FileStream
using (var writer = new StreamWriter(new FileStream(fileName, FileMode.CreateNew)))
writer.Write(myInt.ToString());
if you just want to use a FileStream then things get a bit more manual as you will need to convert things to bytes
using (var stream = new FileStream(fileName, FileMode.CreateNew))
{
var bytes = Encoding.UTF8.GetBytes(myInt.ToString());
stream.Write(bytes, 0, bytes.Length);
}
I'm attempting to use StreamReader and StreamWriter to grab a temporary output log (.txt format) from another application.
The output log is always open and constantly written to.
Unhelpfully if the application closes or crashes, the log file ends up deleted - hence the need for a tool that can grab the information from this log and save it.
What my program currently does is:
Create a new .txt file, and stores the path of that file as the
string "destinationFile".
Finds the .txt log file to read, and stores the path of that file as
the string "sourceFile"
It then passes those two strings to the method below.
Essentially I'm trying to read the sourceFile one line at a time.
Each time one line is read, it is appended to destinationFile.
This keeps looping until the sourceFile no longer exists (i.e. the application has closed or crashed and deleted its log).
In addition, the sourceFile can get quite big (sometimes 100Mb+), and this program may be handling more than one log at a time.
Reading the whole log rather than line by line will most likely start consuming a fair bit of memory.
private void logCopier(string sourceFile, string destinationFile)
{
while (File.Exists(sourceFile))
{
string textLine;
using (var readerStream = File.Open(sourceFile,
FileMode.Open,
FileAccess.Read,
FileShare.ReadWrite))
using (var reader = new StreamReader(readerStream))
{
while ((textLine = reader.ReadLine()) != null)
{
using (FileStream writerStream = new FileStream(destinationFile,
FileMode.Append,
FileAccess.Write))
using (StreamWriter writer = new StreamWriter(writerStream))
{
writer.WriteLine(textLine);
}
}
}
}
}
The problem is that my WPF application locks up and ceases to respond when it reaches this code.
To track down where, I put a MessageBox just before the writerStream line of the code to output what the reader was picking up.
It was certainly reading the log file just fine, but there appears to be a problem with writing it to the file.
As soon as it reaches the using (FileStream writerStream = new FileStream part of the code, it stops responding.
Is using the StreamWriter in this manner not valid, or have I just gone and dome something silly in the code?
Am also open to a better solution than what I'm trying to do here.
Simply what I understand is you need to copy a file from source to destination which may be deleted at any time.
I'll suggest you to use FileSystemWatcher to watch for source file changed event, then just simply copy the whole file from source to destination using File.Copy.
I've just solved the problem, and the issue was indeed something silly!
When creating the text file for the StreamWriter, I had forgotten to use .Dispose();. I had File.Create(filename); instead of File.Create(filename).Dispose(); This meant the text file was already open, and the StreamWriter was attempting to write to a file that was locked / in use.
The UI still locks up (as expected), as I've yet to implement this on a new thread as SteenT mentioned. However the program no longer crashes and the code correctly reads the log and outputs to a text file.
Also after a bit of refinement, my log reader/writer code now looks like this:
private void logCopier(string sourceFile, string destinationFile)
{
int num = 1;
string textLine = String.Empty;
long offset = 0L;
while (num == 1)
{
if (File.Exists(sourceFile))
{
FileStream stream = new FileStream(sourceFile, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
using (new StreamReader(stream))
{
stream.Seek(offset, SeekOrigin.Begin);
TextReader reader2 = new StreamReader(stream);
while ((textLine = reader2.ReadLine()) != null)
{
Thread.Sleep(1);
StreamWriter writer = new StreamWriter(destinationFile, true);
writer.WriteLine(textLine);
writer.Flush();
writer.Close();
offset = stream.Position;
}
continue;
}
}
else
{
num = 0;
}
}
}
Just putting this code up here in case anyone else is looking for something like this. :)
I have a list type of array to store data named PointDataOutput. This list store data of spacial point with (i,j).
How can I save these data?
storing method is in another class:
// Storing method
public void ExportPointData(...)
{
theSpace.TheCells[a,b,0].PointDataOutput.Add(theSpace.TheCells[a,b,0].Temperature);
}
int counter = 0;
for (int currentStep = 1; currentStep <= slnParameter.MaxSteps; currentStep++)
{
// data calculation
theSpace.TheCells[a,b,0].Temperature=....;
// calling method of storing
ExportPointData(...)
}
// saving data in file
if (currentStep == MaxSteps)
{
File.Create("data.txt");
FileStream fs1 = new FileStream("data.txt", FileMode.OpenOrCreate, FileAccess.Write);
StreamWriter writer = new StreamWriter(fs1);
foreach (double x in theSpace.TheCells[a, b, 0].PointDataOutput)
{
writer.WriteLine(x);
}
writer.WriteLine(theSpace.TheCells[a, b, 0].PointDataOutput.ToString);
writer.Close();
}
I don't know can I save data each time it was produce or I should wait to complete iteration and then data in the store List should be saved. I tried several times and each time I got error that there is a text file in the same name of mine!
It shows that each time program makes new file and don't save all data in one file. What should I do?
There are a couple of problems with the code:
The line File.Create("data.txt"); is redundant.
You haven't closed FileStream fs1. It is good practice to close a file
once you have finished with it. A good habit is to use the using keyword
whereever possible.
Taking into account the above, here is how I would implement the 'saving data
in file' section:
// saving data in file
if (currentStep == MaxSteps)
{
using (FileStream fs1 = new FileStream("data.txt", FileMode.OpenOrCreate,
FileAccess.Write))
using (StreamWriter writer = new StreamWriter(fs1))
{
foreach (double x in theSpace.TheCells[a, b, 0].PointDataOutput)
{
writer.WriteLine(x);
}
writer.WriteLine(theSpace.TheCells[a, b, 0].PointDataOutput.ToString);
}
}
//File.Create("data.txt"); you don't need this line
FileStream fs1 = new FileStream("data.txt", FileMode.OpenOrCreate, FileAccess.Write);
problem is File.Create overwritten the existing file every time you call this method
Don't use
File.Create("data.txt");
new FileStream("data.txt", FileMode.OpenOrCreate, FileAccess.Write);
Already creates a new file.
I would get rid of the FileStream entirely, you're creating a file then using the StreamWriter which can already do that and allow you to append to it.
string myFileName = "data.txt";
bool doIWantToAppendToTheFile = true;
StreamWriter writer = new StreamWriter(myFileName, doIWantToAppendToTheFile);
This will then add additional text to your file each time, of course if you didn't want to append just set doIWantToAppendToTheFile to false (oh and change the names, I just named them that way to provide some clarity). If you wanted new files each time the write method was called to have individual blobs of data you could append a datetime stamp to the file name eg:
string myFileName = "data" + DateTime.Now.ToString(yyyyMMdd-hhmmss) + ".txt";
So the filename would be data20140220100430.txt
Here is my code. :
FileStream fileStreamRead = new FileStream(pathAndFileName, FileMode.OpenOrCreate, FileAccess.Read, FileShare.None);
FileStream fileStreamWrite = new FileStream(reProcessedFile, FileMode.OpenOrCreate, FileAccess.Write, FileShare.None);
StreamWriter sw = new StreamWriter(fileStreamWrite);
int readIndex = 0;
using (StreamReader sr = new StreamReader(fileStreamRead))
{
while (!sr.EndOfStream) {
Console.WriteLine("eof" + sr.EndOfStream);
readIndex++;
Console.WriteLine(readIndex);
string currentRecord = "";
currentRecord = sr.ReadLine();
if (currentRecord.Trim() != "")
{
Console.WriteLine("Writing " + readIndex);
sw.WriteLine(currentRecord);
}
else {
Console.WriteLine("*******************************************spaces ***********************");
}
}
It is cutting off 2 lines with one test file and half a line, and then 1 line and half a line with the other test file I am running it against.
I am not a streamreader/writer expert you can probably see.
Any ideas or suggestions would be greatly appreciated as this is driving me batty. I am sure it is me using these incorrectly.
You are missing Flush/Close or simply using for your writer.
using(FileStream fileStreamWrite =
new FileStream(reProcessedFile, FileMode.OpenOrCreate, FileAccess.Write, FileShare.None);
{
using(StreamWriter sw = new StreamWriter(fileStreamWrite))
{
// .... write everything here
}
}
Right after the closing brace of the using statement, do this:
sw.Flush();
sw.Close();
There, that should do it.
You need to Flush your StreamWriter. A StreamWriter has a buffer, and it writes to disk only when the buffer is full. By flushing at the end you make sure all the text in the buffer is written to the disk.
In addition to other answers (use using, and/or flush/close), would say that they do not actually respond to the question: "why it may cut several lines."
I have an idea on subject that it is related to a fact that you use StreamReader and call EndOfStream twice: in a while loop header, and another inside it.
The only possible way of understanding if the stream ends is try to read some data from it. So I suspect EnfOfStream does it, and reading it twice, may create a problem in stream processing.
To resolve an issue:
Or use simple TextReader, considering that you are reading text file (seems to me)
Or change your logic to call only once, so no more call to Console.WriteLine("eof" + sr.EndOfStream);
Or change your logic, so do not use EndOFStream at all, but read line by line till the line is null.
You're not using StreamWriter properly. Also, since you're always reading lines, I would use a method that already does all that for you (and manages it properly).
using (var writer = new StreamWriter("path"))
{
foreach(var line in File.ReadLines("path"))
{
if (string.IsNullOrWhiteSpace(line))
{ /**/ }
else
{ /**/ }
}
}
... or ...
/* do not call .ToArray or something that will evaluate this _here_, let WriteAllLines do that */
var lines = File.ReadLines("path")
.Select(line => string.IsNullOrWhiteSpace(line) ? Stars : line);
var encoding = Encoding.ASCII; // whatever is appropriate for you.
File.WriteAllLines("path", lines, encoding);
for an application that uses a File as some sort of global storage for device reservations in a firm I need a way to read and write to a file (or lock a file, read from it, write to it, and unlock it). A little code snippet will shot what I mean:
FileStream in = new FileStream("storage.bin", FileMode.Open);
//read the file
in.Close();
//!!!!!
//here is the critical section since between reading and writing, there shouldnt
//be a way for another process to access and lock the file, but there is the chance
//because the in stream is closed
//!!!!!
FileStream out = new FileStream("storage.bin", FileMode.Create);
//write data to file
out.Close();
this should get something like this
LockFile("storage.bin");
//read from it...
//OVERwrite it....
UnlockFile("storage.bin");
the method should be absolute safe, since the program should run on 2000 devices at the same time
Simply holding a FileStream open with exclusive (not shared) access will prevent other processes from accessing the file. This is the default when opening a file for read/write access.
You can 'overwrite' a file that you currently hold open by truncating it.
So:
using (var file = File.Open("storage.bin", FileMode.Open))
{
// read from the file
file.SetLength(0); // truncate the file
// write to the file
}
the method should be absolute safe, since the program should run on 2000 devices at the same time
Depending on how often you're writing to the file, this could become a chokepoint. You probably want to test this to see how scalable it is.
In addition, if one of the processes tries to operate on the file at the same time as another one, an IOException will be thrown. There isn't really a way to 'wait' on a file, so you probably want to coordinate file access in a more orderly fashion.
You need a single stream, opened for both reading and writing.
FileStream fileStream = new FileStream(
#"c:\words.txt", FileMode.OpenOrCreate,
FileAccess.ReadWrite, FileShare.None);
Alternatively you can also try
static void Main(string[] args)
{
var text = File.ReadAllText(#"C:\words.txt");
File.WriteAllText(#"C:\words.txt", text + "DERP");
}
As per http://msdn.microsoft.com/en-us/library/system.io.fileshare(v=vs.71).aspx
FileStream s2 = new FileStream(name, FileMode.Open, FileAccess.Read, FileShare.None);
You need to pass in a FileShare enumeration value of None to open on the FileStream constructor overloads:
fs = new FileStream(#"C:\Users\Juan Luis\Desktop\corte.txt", FileMode.Open,
FileAccess.ReadWrite, FileShare.None);
I ended up writing this helper class to do this:
public static class FileHelper
{
public static void ReplaceFileContents(string fileName, Func<String, string> replacementFunction)
{
using (FileStream fileStream = new FileStream(
fileName, FileMode.OpenOrCreate,
FileAccess.ReadWrite, FileShare.None))
{
StreamReader streamReader = new StreamReader(fileStream);
string currentContents = streamReader.ReadToEnd();
var newContents = replacementFunction(currentContents);
fileStream.SetLength(0);
StreamWriter writer = new StreamWriter(fileStream);
writer.Write(newContents);
writer.Close();
}
}
}
which allows you to pass a function that will take the existing contents and generate new contents and ensure the file is not read or modified by anything else whilst this change is happening
You are likely looking for FileStream.Lock and FileStream.Unlock
I think you just need to use the FileShare.None flag in the overloaded Open method.
file = File.Open("storage.bin", FileMode.Open, FileShare.None);