[RESOLVED] how to move between lines when writing to a text file

i am using the following code to write to a text file

Code:

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dim A1 as string

A1= "......."

On Error GoTo l1
Open App.Path & "\Textfile.txt" For Append As #1
l1:
On Error GoTo l2
Print #1, A1
Close #1
l2:

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which go down to a new line each time its used, however at some points i need to go back and complete to the first line an additional string and then go back down.
how can i move between lines, and to the specific point?

I believe that you can not achieve what you wish using the simple code you quote. The OPEN statement allows three options - For Input, For Output and For Append. Only the last of these - APPEND - allows the addition of text and as the name implies it can only be added at the end.

I have solved this problem by the use of a RichTextBox. Place a large RTBox on your form and then import your txt file into it. You can then read it all and edit it much as when using MS Word or Notepad or Wordpad in word-processing. Thus you can add text at the bottom, in the middle and at the beginning. Also you can change any of the text already written. When you have completed what you want to do with your text, you then save it back into your Textfile.txt path and that will then contain the version as you have just modified it.

I find the RTBox a powerful and very useful control, but one which seldom gets much (or any) mention in a lot of VB6 books.

If you need help with the code to achieve the above with a RTBox, make another post to this thread and I will generate an example.

camoore

Wales, UK

Text files are written top to bottom. If you need to change something in a text file then you read the file and write it again adding what you need to at the proper time during the write or to the string before it is written.

Datamiser has repeated the concept of my advice. Using simple code you can only append new text at the end of a .txt file. To do otherwise requires the file to be "read" into some sort of string variable (I suggested the RichTexBox) manipluated and then saved (re-read) back as the original file.txt path.

Manipulation can be carried out under VB6 if you subsequently copy the RTBox file into a String variable and then use String Manipulation to change this automatically.

In order to do this you would need a very rigidly defined format for your source .txt file - in order that String Manipulation could accurately and unambiguously determine which element of the String (=.txt file) you want to change or add to.

camoore

Wales, UK

If you know the line # to modify then it easy you can read entire file line by line and add a counter when your counter hits your line number you append to file

Code:

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Private Sub Command1_Click()
Dim sLineText As String
Dim sTemp as String
Dim ff As Integer
Dim iLineCount As Integer



Open "C:\textfile.txt" For Input As #ff
  Do While Not EOF(ff)
      Line Input #ff, sLineText
      sTemp = sTemp & sLineText & vbNewLine
      iLineCount = iLineCount + 1
If iLineCount = 4 Then
sTemp = sTemp & "My string to add." 'here i append to the file on line 4
End If
  Loop
Close #ff

sTemp = Left(sTemp,Len(sTemp) - 1) 'Remove last vbNewLine

Open "C:\textfile.txt" For Output As #ff
Print #ff, sTemp
Close #ff
End Sub

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This is one of the ways if you know where to append if not you will need to search for string and then append after the string

Yes and there are other ways as well.

If your file has fixed lenght lines then it is easy to modify an existing line so long as you know the line number, not that it is hard using the ways given just requires a few more steps. If a file has fixed lenght records then you can use Random Access and read or write to any line in the file without the need to create a new file or read anything other than the line in question.

Quote:

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you can then read it all and edit it much as when using MS Word or Notepad

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but i dont want to make these changes manually. because i cant. it's a numerous number of equations with varying variables and coefficients according to ather factors.

so i guess ill ask the question again, how to move between lines in richtextbok and how to add texts at specific places programatically

amd711. Then you have not adequately described what you want to do.

There are many ways of using VB6 to modify a .txt document, and the best method to adopt depends upon just what you want to achieve.

Please define your requirement more exactly. Programming is an exact "science" but it can only be accomplished exactly given an exact definition of the objective.

All of the replies to your post relate to string management, but strings can only be "managed" if you define EXACTLY how you want to manage them.

camoore

Wales, UK

Quote:

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Originally Posted by amd711

but i dont want to make these changes manually. because i cant. it's a numerous number of equations with varying variables and coefficients according to ather factors.

so i guess ill ask the question again, how to move between lines in richtextbok and how to add texts at specific places programatically

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You would read the file line by line using the line input # method. You would write these lines out to a new file as you go. When you get to a line you want to modify you make your change to that line which would be in the form of a string variable in memory then you write the modified line to the new file instead of the original line then continue on until you have did all the lines in the file. Nothing complicated about it you just have to read and write top to bottom making changes at the proper time. Once your line is written to the file you can not go back and edit that line wihtout once again reading the file and writing the changed file again.

Code:

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Dim InFileHandle as Integer
Dim OutFileHandle as Integer

Dim TheLine as String
Dim LineNumber As Integer

InFileHandle=FreeFile
Open InputFileName For Input As #InFileHandle
OutFileHandle=FreeFile
Open OutputFileName for Output as #OutFileHandle

Do While Not EOF(InFileHandle)
    LineNumber=LineNumber+1
    Line Input #InFileHandle,TheLine
    if LineNumber=YourTargetLineNumber
        'Make changes to TheLine here
    End If
    Print #OutFileHandle, TheLine
Loop
Close #OutFileHandle
Close #InFileHandle

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As cadmoor has pointed out, there are numerous methods to edit data. From what you've told us so far it's just about impossible to recommend the 'best' solution. The fact that you're not using something like Notepad implies that it's not just a simple matter of going through lines of the file making changes manually.

So, how will you identify candidates for change?
Will there be 'global' changes (eg change all X ^2 to X ^ 3 in all records)?
Do you need to see the data before and after changes or should it all be done 'behind the scenes'?
Do you need to save the original file or make changes 'in situe', thus losing the original data?

If you can answer those questions it'll give people a better idea of how to guide you.

Quote:

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how will you identify candidates for change?

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changes will be at the first line only, and I won't change it completely i will continously add to it

Quote:

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Do you need to see the data before and after changes or should it all be done 'behind the scenes'?

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no i dont

Quote:

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Will there be 'global' changes (eg change all X ^2 to X ^ 3 in all records)?

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like i said, the first line only, an addition will be added to it each time an equation is built below.

Quote:

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Do you need to save the original file or make changes 'in situe', thus losing the original data?

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there won't be an original file every thing will be built from scratch.

Ok, if I understand you correctly you are going to add records to a file a line at a time. Once a line has been added to the file you will not want to change that line. If that's correct then it's a reasonably simple matter to collect the input (ie the data you're going to add), open the file for Append and Print the data to the file, repeat until all the data has been Printed to the file, then close the file. If the input is coming from the user (e.g. they're typing it into a TextBox then you'll need some way of determining when they've finished. In its simplest form it might look something like this:

Code:

---

Option Explicit
Private intFile As Integer

Private Sub cmdAdd_Click()
'
'
' When the user clicks on cmdAdd it will output
' the contents of the textbox to the file
' unless it was a blank line in which case
' the file is closed
' and the program exits
'
If txtEquation.Text <> "" Then
    Print #intFile, txtEquation.Text
    txtEquation.Text = ""
Else
    Close intFile
    MsgBox "Additions to the file are complete"
    Unload Me
End If
End Sub

Private Sub Form_Load()
'
' At start up clear the textbox and open the file
'
txtEquation.Text = ""
intFile = FreeFile()
Open "C:\MyData\Equations.text" For Append As intFile
End Sub

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I still fail to understand fully what the OP wants. He has stated that he wants "continuously to add to the first line only" yet has also stated that "there will not be an original file. Everything will be built from scratch".

If there is no original file, then what first line is to be added to?

If the whole file is being generated from code each time "something" takes place, then the code to generate the first line must be in the program and he simply needs to alter what that code writes as the first line.

If after starting to compile the file by code the first line needs to be changed/added to, then why not simply start from scratch again?

Even this could be avoided. Have 2 text boxes, one for the first line, the other for the rest of the file. If it becomes necessary as a result of subsequent action(s) to alter the first line, then just amend the first text box. Then when all action(s) are complete, join the string of the second text box to that of the first and save the lot as a new .txt.

Is that not more simple?

camoore

Wales, UK

big thanks to you all
especially camoore, Thanks alot :)

Pleased that we were able to be of assistance. If your problem is now solved, please mark the thread as RESOLVED (see thread tools at the top).

camoore

Wales, UK