File writes in a loop

[AdemusPrime]

I need to write data to a file in a loop. I get a "file already in
use" error on the second loop. The problem is, I don't know the name
of the file until I'm in the loop. How can I keep a file open for
writing in a loop?

while ((data = log.ReadLine()) != null)
{
string date = data.Substring(0, 10);
FileStream fileOut = new FileStream(dir + date + name,
FileMode.OpenOrCreate, FileAccess.Write);

fileOut.Write(Encoding.UTF8.GetBytes(data), 0, data.Length);
fileOut.Flush();
}

[Hilton]

while ((data = log.ReadLine()) != null)
{
string date = data.Substring(0, 10);
using (FileStream fileOut = new FileStream(dir + date + name,
FileMode.OpenOrCreate, FileAccess.Write))
{
byte[] bytes = Encoding.UTF8.GetBytes(data);
fileOut.Write(bytes, 0, bytes.Length);
}
<Ad*********@gmail.comwrote in message
news:bc**********************************@l64g2000 hse.googlegroups.com...

>I need to write data to a file in a loop. I get a "file already in
use" error on the second loop. The problem is, I don't know the name
of the file until I'm in the loop. How can I keep a file open for
writing in a loop?

while ((data = log.ReadLine()) != null)
{
string date = data.Substring(0, 10);
FileStream fileOut = new FileStream(dir + date + name,
FileMode.OpenOrCreate, FileAccess.Write);

fileOut.Write(Encoding.UTF8.GetBytes(data), 0, data.Length);
fileOut.Flush();
}

[parez]

On May 16, 3:35 pm, [e-mail] wrote:

I need to write data to a file in a loop. I get a "file already in
use" error on the second loop. The problem is, I don't know the name
of the file until I'm in the loop. How can I keep a file open for
writing in a loop?

while ((data = log.ReadLine()) != null)
{
string date = data.Substring(0, 10);
FileStream fileOut = new FileStream(dir + date + name,
FileMode.OpenOrCreate, FileAccess.Write);

fileOut.Write(Encoding.UTF8.GetBytes(data), 0, data.Length);
fileOut.Flush();

}

are you going have multiple files open in the loop?if yes and you
dont want to close them then you could
use a a hashtable and use dir + date + name as the key and the
filestream as the object.

[zacks]

On May 16, 3:35*pm, [e-mail] wrote:

I need to write data to a file in a loop. I get a "file already in
use" error on the second loop. The problem is, I don't know the name
of the file until I'm in the loop. How can I keep a file open for
writing in a loop?

while ((data = log.ReadLine()) != null)
{
string date = data.Substring(0, 10);
FileStream fileOut = new FileStream(dir + date + name,
FileMode.OpenOrCreate, FileAccess.Write);

fileOut.Write(Encoding.UTF8.GetBytes(data), 0, data.Length);
fileOut.Flush();

}

Your question is cryptic, so I am just guessing here but maybe you
need a:

fileOut.Close();

after the flush?

And maybe even a:

fileOut.Dispose();

[AdemusPrime]

Thank you for the reply.

This code will close, dispose and reopen the file on each loop.
Therefore, after each loop there is only one record in the output file
which is a last write.

[AdemusPrime]

Not sure which part is cryptic. I need to open the file for writing
and keep it open in a loop.

I can close and/or dispose the object but I want to keep the file open
for writing instead of making roundtrip opens/closes each time. Plus,
i would have to advance the cursor to the end of the file each time I
open it, which could be big.

[Paul E Collins]

<Ad*********@gmail.comwrote:

I need to write data to a file in a loop. I get a "file already in
use" error on the second loop.

You aren't closing the file. After calling Flush, call Close.

Eq.

[Peter Duniho]

On Fri, 16 May 2008 13:08:07 -0700, <Ad*********@gmail.comwrote:

Not sure which part is cryptic. I need to open the file for writing
and keep it open in a loop.

You keep saying "the file", but then you also imply that you may have more
than one file.

I can close and/or dispose the object but I want to keep the file open
for writing instead of making roundtrip opens/closes each time.

If you have more than one file you might open in the loop, then you need
to keep track of all the files you've opened. You've already been
provided suggestions for doing that.

If you only have one file, then I recommend putting the FileStream
variable outside the loop, initialized to null, and creating the
FileStream instance only if the variable is null. If it's not null, just
use the current value of the variable.

Plus,
i would have to advance the cursor to the end of the file each time I
open it, which could be big.

The size of the file make absolutely no difference with respect to
seeking. You could in fact close and reopen the file each iteration of
the loop, seeking to the end of the file before writing each time (or just
use FileMode.Append instead of OpenOrCreate). The only real performance
overhead would be the act of opening and closing the file; the seeking
isn't a problem at all.

But the fact is, there's not any need to reopen the file each time through
the loop. Whether you have more than one file or not, there is a
perfectly good solution that doesn't involve reopening the file with each
iteration of the loop.

Pete

[Joe Cool]

On Fri, 16 May 2008 13:08:07 -0700 (PDT), Ad*********@gmail.com wrote:

>Not sure which part is cryptic. I need to open the file for writing
and keep it open in a loop.

I can close and/or dispose the object but I want to keep the file open
for writing instead of making roundtrip opens/closes each time. Plus,
i would have to advance the cursor to the end of the file each time I
open it, which could be big.

You need to close the file after flushing it. If you need to add to
the file in a subsequent iteration, I would first check to see if the
file exists yet or not with the File.Exists method.

If if does not exist, open the file for create or open. If it does,
open it for append.

[Cor Ligthert[MVP]]

Joe,

In my idea do you give the best solution

(This in fact to the OP to try this first).

Cor

"Joe Cool" <jo*****@home.netschreef in bericht
news:ph********************************@4ax.com...

On Fri, 16 May 2008 13:08:07 -0700 (PDT), Ad*********@gmail.com wrote:

>>Not sure which part is cryptic. I need to open the file for writing
and keep it open in a loop.

I can close and/or dispose the object but I want to keep the file open
for writing instead of making roundtrip opens/closes each time. Plus,
i would have to advance the cursor to the end of the file each time I
open it, which could be big.

You need to close the file after flushing it. If you need to add to
the file in a subsequent iteration, I would first check to see if the
file exists yet or not with the File.Exists method.

If if does not exist, open the file for create or open. If it does,
open it for append.

[AdemusPrime]

This is what I ended up with.

using (StreamReader log = File.OpenText(myArgs["i"]))
{
FileStream outFile = null;
string old = string.Empty;
while ((data = log.ReadLine()) != null)
{
string date = data.Substring(0, 10);
if (old != date)
{
if (outFile != null)
{
outFile.Close();
}
outFile = new FileStream(dir + date +
name, FileMode.Append, FileAccess.Write);
old = date;
}
outFile.Write(Encoding.UTF8.GetBytes(data), 0,
data.Length);
outFile.Write(Encoding.UTF8.GetBytes("\r\n"),
0, 2);
outFile.Flush();
}
outFile.Close();
}