Need To Write String/Number To A File

Posted on 1999-01-05
Last Modified: 2010-05-03
Hello, I am trying to write a "string/number" combination to a file. Like "Hello=12". I need to know where "Hello=10" is in the file so I can change this to "Hello=12". I am using Visual Basic 5.0 and am very lacking (novice) for now. Thank You for you time !
Question by:amyy
  • 2

Accepted Solution

cyber_bandit earned 100 total points
ID: 1454049
Open "myfile.txt" as #1 for input
Print #1, "hello=10"
Close #1
' this will open a file and write the requested text to it

Open "myfile.txt" as #1 for output
Line Input #1, mytext
Close #1
' That is read the first line of the text in, each Line Input statement after the 1st line will read the next line of the file in.

Do some simple string manipulation to change the 10 to 12 and then reopen the file and write it back.
LVL 10

Expert Comment

ID: 1454050
Hello amyy

Cyber Bandit's answer is probably not what you're looking for as he doesn't give you a method to find the text in the file and replace it.

The following does that for you:

Private Sub Command1_Click()

Dim strW As String
Dim intLen As Integer
Dim intPos As Integer

'First, read the contents of the file into memory
intLen = FileLen("C:\Fred.txt")

Open "C:\Fred.txt" For Input As #1
strW = Input(intLen, #1)
Close #1

'Then find "Hello=10"
intPos = InStr(strW, "Hello=10")

'If found, replace with "Hello=12"
If intPos = 0 Then
    Exit Sub
End If

strW = Left(strW, intPos - 1) & _
       "Hello=12" & _
       Right(strW, Len(strW) - intPos - Len("Hello=10") + 1)

Open "C:\Fred.txt" For Output As #1
Print #1, strW;
Close #1

End Sub

LVL 10

Expert Comment

ID: 1454051
Basically what the above file does is read the complete file into one long big string.

Once that is done, the program uses the Instr function to locate the string "Hello=10" within that big string.

Let's say, that your file contains

it breaks the string up into blahblahbefore and blahblahafter and rebuilds it as


Then it writes the whole lot back into the file, overwriting anything that might already be there.

The net result of the whole thing is that it seems as if "Hello=10" is replaced with "Hello=12" in your file.

PS - Proper file handling dictates the use of "FreeFile" for opening and closing files but I've not done that here as it might confuse matters - er... how novice are you exactly?
I also haven't catered for multiple occurrences of "Hello=10"; that would complicate matters even further. But if you're interested, let me know.

Expert Comment

ID: 1454052
Your text file looks like a .ini file with key=value lines; just append sections in the file and...

If so, you could use standard API functions to access it using the following code:

Private Declare Function GetPrivateProfileString Lib "kernel32" Alias "GetPrivateProfileStringA" (ByVal lpApplicationName As String, ByVal lpKeyName As Any, ByVal lpDefault As String, ByVal lpReturnedString As String, ByVal nSize As Long, ByVal lpFileName As String) As Long
Private Declare Function WritePrivateProfileString Lib "kernel32" Alias "WritePrivateProfileStringA" (ByVal lpApplicationName As String, ByVal lpKeyName As Any, ByVal lpString As Any, ByVal lpFileName As String) As Long

private sub Command_click()
  'this command replace the current Hello=10 by Hello=12
  'in the file, or create the line if it not exists.
  WritePrivateProfileString "theSection", "Hello", "12", "myfile.txt"
end sub

Featured Post

The Eight Noble Truths of Backup and Recovery

How can IT departments tackle the challenges of a Big Data world? This white paper provides a roadmap to success and helps companies ensure that all their data is safe and secure, no matter if it resides on-premise with physical or virtual machines or in the cloud.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

When trying to find the cause of a problem in VBA or VB6 it's often valuable to know what procedures were executed prior to the error. You can use the Call Stack for that but it is often inadequate because it may show procedures you aren't intereste…
Enums (shorthand for ‘enumerations’) are not often used by programmers but they can be quite valuable when they are.  What are they? An Enum is just a type of variable like a string or an Integer, but in this case one that you create that contains…
Get people started with the utilization of class modules. Class modules can be a powerful tool in Microsoft Access. They allow you to create self-contained objects that encapsulate functionality. They can easily hide the complexity of a process from…
Show developers how to use a criteria form to limit the data that appears on an Access report. It is a common requirement that users can specify the criteria for a report at runtime. The easiest way to accomplish this is using a criteria form that a…

778 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question