VB.NET - how to add lines at the top of text file

[mishaluba]

Hello,

I need to add a few lines at the TOP of the existing file (create missing file headers). How can I do this?

Thank you!

vb.net newby

[cyberdaemon]

Hello,

I need to add a few lines at the TOP of the existing file (create missing file headers). How can I do this?

Thank you!

vb.net newby

Ok I have been working on this, it was fun. I was real close to not have to brute force the add, but it was still cutting part of the file out. So this is probably the worst way to do this but:

[CODE=vbnet]Private Sub AddHeader()
' Append to TOP
Dim _FStream As New System.IO.FileS tream("C:\Heade rfile.txt", IO.FileMode.Ope n, IO.FileAccess.R eadWrite, IO.FileShare.Re adWrite, 32, IO.FileOptions. RandomAccess)
Dim _Reader As New System.IO.Strea mReader(_FStrea m)

Dim AppendVal As String = ""
Dim CurVal As String = ""

AppendVal = "APPENDED HEADER LINE 1"

' Read old file in, then Place the Header at the beginning of the stream
_FStream.Seek(0 , IO.SeekOrigin.B egin) ' Set the stream to the beginning of the file
_Reader = New IO.StreamReader (_FStream)
While Not _Reader.EndOfSt ream
CurVal &= Convert.ToChar( _Reader.Read)
End While
AppendVal &= vbNewLine & CurVal
_Reader.Close()

' Write file with header
_FStream = New System.IO.FileS tream("C:\Heade rfile.txt", IO.FileMode.Ope n, IO.FileAccess.W rite, IO.FileShare.No ne, 32, IO.FileOptions. None)
Dim _Writer As New System.IO.Strea mWriter(_FStrea m)
_FStream.Seek(0 , IO.SeekOrigin.B egin) ' Set the stream to the beginning of the file
_Writer = New IO.StreamWriter (_FStream)
_Writer.WriteLi ne(AppendVal)

_Writer.Close()
End Sub[/CODE]

it can be easily modified to accept a parameter for the header string.
To Use: Simply add the lines to AppendVal, if multiple line then

[CODE=vbnet]Appendval = "Line 1" & controlchars.ne wline & "Line 2" & controlchars.ne wline & "Line 3"[/CODE]

it works. Play with it, let me know if you shorten it. I had it shorter, then I received an error so I added a few lines to make it more robust.

also change the path to where the file is, this can become a parameter as well. Anyway thanks for the challenge. Hope this works for you good luck and happy coding

Cyberdaemon

[vanc]

Make it simpler:
1. Create a new file called NewFileWithHead er
2. Write headers into new file
3. Open original file
4. Append the content of original file to new file
5. Close original file
6. Close new file
7. Delete original file
8. Rename new file to the same name original file

cheers.

[mishaluba]

OK, I finally found the time to do this. Cyberdaemon, thank you very much for the code, it got me started in the right direction. Here is what is working for me -- basically the same approach, maybe a bit more streamlined:

Dim sHeaderFile As String = "c:\MyHeaderFil e"
Dim sMyBatchFile As String = "c:\myBatchFile "
Dim sHeaderText As String
Dim sSplitBatchText As String
Dim sResult As String = ""

' Declare Stream object to read header file and point it to our header file
Dim fStream_Header As New System.IO.FileS tream(sHeaderFi le, IO.FileMode.Ope n, IO.FileAccess.R ead)
' Declare Stream reader object and at the same time read the header file in
Dim fsStreamReader_ Header As New System.IO.Strea mReader(fStream _Header)

' Read the header
sHeaderText = fsStreamReader_ Header.ReadToEn d

' Declare Stream object to read batch file and point it to our batch file
Dim fStream_BatchFi le As New System.IO.FileS tream(sMyBatchF ile, IO.FileMode.Ope n, IO.FileAccess.R eadWrite)
' Declare Stream reader object and at the same time read the batch file in
Dim fsStreamReader_ BatchFile As New System.IO.Strea mReader(fStream _BatchFile)

' Read the batch file
sSplitBatchText = fsStreamReader_ BatchFile.ReadT oEnd

' Append the header in front of the batch file text
sResult = sHeaderText & vbNewLine & sSplitBatchText

' Point our stream back to the beginning of the file
fStream_BatchFi le.Seek(0, IO.SeekOrigin.B egin)
' Declare Stream writer object and point it to the batch file, we are now looking at the beginning of the file
Dim fsStreamWriter_ BatchFile As New System.IO.Strea mWriter(fStream _BatchFile)

' Write our result back to the batch file
fsStreamWriter_ BatchFile.Write (sResult)

' Clean up
fsStreamReader_ Header.Close()
' Since both StreamReader and StreamWriter point to the same file, we only need to close one of them
' fsStreamReader_ BatchFile.Close ()
fsStreamWriter_ BatchFile.Close ()

Dts.TaskResult = Dts.Results.Suc cess

[Plater]

hmm
If you have a file called "a.txt" and "b.txt" then run the system command
"copy ?.txt both.txt"

both.txt will then contain the contents of a.txt followed by b.txt

[sudhakarkintala]

Thanks... This script is very helpful for me.. The script is throwing error if the file size is more than 500MB .. Can you please help me on how to handle big files for more than 500 Mb.. i am getting out of memory exception error