I have a problem reading two lines from a stream reader. I want to read the first line and then proceed to the next one. Here's my code:
Public Function Read()
Dim a As New MemoryStream(ASCII.GetBytes("[ID] " & vbCrLf & " salut" & vbCrLf))
Debug.Print(client.ReadLine(a))
Debug.Print(client.ReadLine(a))
End Function
Public Function ReadLine(ByVal Data As MemoryStream)
Dim sr As New StreamReader(Data)
Return sr.ReadLine
End Function
The output is:
[ID]
One line. I checked the stream in debug mod and I've seen that the position was 15 after the first ReadLine call. So I have to move the "pointer" after the first VbCrLf(that's all the way to the end). But I don't think that's the proper way of doing it. Where am I wrong? I even passed the stream by value so it should've worked.
EDIT
I made some checks and it seems that and only when passing a stream the position moves to the end. I created a stream reader in the same Read function and passed as parameter the a memory stream. It worked. I don't know why this happen. I'm still looking for an answear.
It is not clear what you are really trying to do, but you are not really trying to read two lines from [a] StreamReader, you are trying to read one line at a time from two different streamreaders using the same data source/buffer.
Dim buff = Encoding.ASCII.GetBytes("[ID] " & vbCrLf & " salut" & vbCrLf)
Using ms As New MemoryStream(buff)
Using sr As New StreamReader(ms)
Console.WriteLine(sr.ReadLine())
Console.WriteLine("memstream poition: " & ms.Position)
Console.WriteLine(sr.ReadLine())
Console.WriteLine("memstream poition: " & ms.Position)
Console.WriteLine(sr.ReadLine())
End Using
End Using
If you set a breakpoint on the first sr.ReadLine(), you'll see that the MemoryStream position has changed. If you mouse over the srvariable, you'll see why:
Streamreader has a buffer, 1024 bytes by default. You can compare that buffer to the one created in code and see they are the same. There is also a StreamReader overload which allows you to specify the size:
Public Sub New(stream As System.IO.Stream,
encoding As System.Text.Encoding,
detectEncodingFromByteOrderMarks As Boolean,
bufferSize As Integer)
Trying to read from a single data stream with different (new) StreamReaders wont work because the previous one will have already consumed some of the data. You should be able to read many thousands of lines into an array or list which your code can use as a line-buffer.
Related
I am trying to read specific lines from a text file in an array (e.g. line 16,25,34, and so on). Could you please let me know if it is possible and how that could be done?
Thanks in advance,
Pouya
Yes it is possible. Since this is not a code based will elaborate how to achieve that. This will depends on the size of your target file. If the size in not to large for your PC's memory then you can read the whole textfile while reading keep the count.
Then start when the file has been read to end to go through your lines using regex.
Check:
VB.NET Read Certain text in a text file
your solution is here:
http://www.dreamincode.net/forums/topic/56497-go-to-a-particular-line-in-a-text-file-using-vbnet/
How to read a specific line from a text file in VB
Ok, here's I've also quoted the code to help you from the second last like I provided above. I'm sure you know how to get data from an Array so instead of line you will add your array.
Public Function
ReadSpecifiedLine(ByVal line As
Integer) As String
'create a variable to
hold the contents of the file
Dim contents As String = String.Empty
'create a variable to
hold our line contents
Dim lineText As String =
String.Empty
' always use a
try...catch to deal
' with any exceptions
that may occur
Try
'Using lineByLine As New IO.StreamReader(_fileName)
Dim lineCount As Integer = 0
While Not lineByLine.EndOfStream
lineByLine.ReadLine ()
If lineCount = line Then
' you can replace the line variable above or use the And Or to match the lines from your array.
lineText = lineByLine.ReadLine()
End If
lineCount += 1
End While
End Using
Catch ex As FileNotFoundException
lineText = String.Empty
_returnMessage = ex.Message
Catch ex As Exception
' deal with any errors
_returnMessage = ex.Message
End Try
Return lineText
End Function
Hope this helps you.(Sorry having some problems in code formatting it some part maybe not formeted, or visible. If End Function is not visible please refer to the link. I've tried so many times to formet this but it not properly formeted, I'm using a Mobile phone.)
I have a program that needs to look through a text file line by line, the lines look like this:
10-19-2015 Brett Reinhard All Bike Yoga Run the Studio Design Your Own Strength
These are separated by tabs in the text file.
What I want to do is look at the second value, in this case "Brett Reinhard" and move the full line to another textfile called "Brett Reinhard"
I was thinking of using an array to check to see if the second 'column' in the line matched any value within a given array, if it does I want to perform a specific action.
The way I am thinking of doing this is with a For/next statement, now while it will work it will be a laborious process for the computer that I will be using it on.
The code I am thinking of using looks like this:
For intCounter=0 to Whatever Number is the last number of the array
If currentfield.contains(array(intCounter)) Then
Open StreamWriter(File directory & array(intcounter) & ".txt")
Streamwriter.Writeline(currentfield)
End IF
Is there a better way of doing this, such as referencing the second 'column' in the line, similar to the syntax used in VBA for excel.
Name=Cells(1,2).Value
If you can guarantee that a line will only use the tab characters as field separators, you can do something along this:
Open the stream for reading text
Open a stream for writing text
Read a line of text
Use the Split method to break the incoming line into an array of fields
If the second element in the array is your sentinel value, write the original line to the writer
Repeat yourself until you have reached the end of file (ReadLine will return Nothing, or null for those c# folk).
Close and dispose of your stream objects.
If you aren't sure of the format, you will want to take the hit and use the TextFieldParser as mentioned in an earlier comment.
So while its not using an array to search a file, what I ended up doing works just as well. I ended up using the split method thanks to #Martin Soles.
Here is what I came up with:
Sub Main()
Dim intCount As Integer = 1
Dim words As String
Dim split As String()
Using MyReader As New Microsoft.VisualBasic.
FileIO.TextFieldParser(
"I:\Games, Events, & Promotions\FRP\Back End\Approved.txt")
MyReader.TextFieldType = FileIO.FieldType.Delimited
MyReader.SetDelimiters(",")
Dim currentRow As String()
While Not MyReader.EndOfData
Try
currentRow = MyReader.ReadFields()
Dim currentField As String
For Each currentField In currentRow
words = currentField
split = words.Split(New [Char]() {CChar(vbTab)})
For Each s As String In split
If intCount = 2 Then
Dim file As System.IO.StreamWriter
file = My.Computer.FileSystem.OpenTextFileWriter("I:\Games, Events, & Promotions\FRP\Back End\" & s & ".txt", True)
file.WriteLine(currentField)
file.Close()
End If
intCount = intCount + 1
Next s
intCount = 1
Next
Catch ex As Microsoft.VisualBasic.
FileIO.MalformedLineException
MsgBox("Line " & ex.Message &
"is not valid and will be skipped.")
End Try
End While
End Using
End Sub 'Main
Thank you guys for the suggestions.
For right now the split method will work for what is needed.
I'm trying to write the content of my textbox to a txt file.
My code works fine but my error is, when I open txt file I see
writeline1writeline2writeline3
instead of
writeline1
writeline2
writeline3
my code;
result As List(Of String) = New List(Of String)
convertedText.Lines = result.ToArray()
My.Computer.FileSystem.WriteAllText(mypath & "\convertedcontent.txt", convertedText.Text, False)
Writing to .csv and many other file types work fine but I don't know how to break lines for text file.
Thanks in advance
I would use System.IO.File.WriteAllLines:
Dim path = System.IO.Path.Combine(mypath, "convertedcontent.txt")
System.IO.File.WriteAllLines(path, result)
Otherwise you need to append Environment.NewLine to each line, you can use String.Join:
System.IO.File.WriteAllText(path, String.Join(Environment.NewLine, result))
You need to add & vbCrLf to your strings (each line)
Not sure where you are getting your strings from.. but you will have to add the carrier return/Line Feed character to those strings, one at the end of every string.
Might just even loop through your array and add them there?
P.S. Some of the comments have quicker ways of getting there, but this is probably what happens behind the scenes...
for i = 0 to convertedText.Lines.count -1
convertedText.Lines(i) += vbCrLf
next
I have the following code that I am using to parse out a test file. I am getting variable conversion error in Sub Main() when I assign file = Read(). The return value of Read() is a TextFieldParser type. How do I assign the proper variable type to "file" so I can write the output to a text file?
Thanks!
Module Module1
Function Read()
Using MyReader As New FileIO.TextFieldParser("C:\Users\Colin\Desktop\Parse_Me.txt")
Dim currentRow As String
While Not MyReader.EndOfData
Try
currentRow = MyReader.ReadLine()
Console.WriteLine(Parse_me(currentRow))
Catch ex As FileIO.MalformedLineException
MsgBox("Line " & ex.Message &
" is invalid. Skipping")
End Try
End While
Return MyReader
MyReader.Close()
End Using
End Function
Function Parse_me(ByVal test As String)
Dim Set_1, Set_2, Set_3, Set_4, Set_5 As String
Dim new_string As String
Set_1 = test.Substring(0, 4)
Set_2 = test.Substring(7, 2)
Set_3 = test.Substring(11, 1)
Set_4 = test.Substring(14, 4)
Set_5 = test.Substring(20, 4)
new_string = Set_1 & " " & Set_2 & " " & Set_3 & " " & Set_4 & " " & Set_5
Return new_string
End Function
Sub Main()
Dim file As Object
file = Read()
FilePutObject("C:\Users\Colin\Desktop\Parse_Meoutput.txt", file)
End Sub
End Module
Here's how FilePutObject is supposed to work (example taken from MSDN documentation for FilePutObject):
Sub WriteData()
Dim text As String = "test"
FileOpen(1, "test.bin", OpenMode.Binary)
FilePutObject(1, text)
FileClose(1)
End Sub
The 1 act as an identifier for the file. Note also that the file name is passed to FileOpen before calling FilePutObject, and that FileClose is called afterwards. Also note that a string is being written to the file. I don't know which types of data are valid for being passed to FilePutObject, but FileIO.TextFieldParser is definitely not one of them (I just tried it).
Correct me if I'm wrong, but I'm pretty sure that FilePutObject is one of those carry-overs from VB6. If you're writing new code, I would rather use a Stream object for my I/O. For one, it's a lot more .Net-ish (i.e., type-safe, object-oriented, etc). And as far as usability goes, it's a lot clearer how a Stream works, not to mention it doesn't involve passing arbitrary integers as handles to functions in order to identify which file you'd like to work with. And to top it all off, a Stream works whether you want to write to a file, to the console, or send the data to another machine. To sum up, I would definitely look up the Stream class, some of its child classes (like FileStream, and whatever else appeals to you), and some associated types (such as the TextWriter class for conveniently writing text).
Change the definition of the function "read" to:
Function Read() as FileIO.TextFieldParser
and change the declaration of "file" in sub main to:
Dim file as FileIO.TextFieldParser
That way the data type of the function and assignment match.
I am curious. If I am using a combination of streamreader and streamwriter is there a way that I can have a stream written only if File X has been modified?
This code may not be constructed in the best way. It is attached to help in getting my questions accross.
sCommand = "whoami.exe >> C:\Desktop\Test.txt"
Using swrr As New StreamWriter(File.Open(ErrorLog, FileMode.OpenOrCreate))
For Each strUserName As String In strLines
Shell("cmd.exe /c" & sCommand, AppWinStyle.Hide, True, )
'command Cannot Execute, List Why and Move onto Next Command
Using sr As New StreamReader(File.Open(Test.txt, FileMode.OpenOrCreate))
If '''??File has been modifed??''''' Then swrr.WriteLine("PASS") Else swrr.WriteLine("FAIL")
End Using
Next
End Using
You can call File.ReadAllText(path) to get a string containing the text.
You can then compare the new string to the old one.
The correct way to read the output of a command is to use the Process class with RedirectStandardOutput.
You can then create a StreamReader around StandardOutput and call ReadToEnd().