powershell - replace line in .txt file

Question

I am using PowerShell and I need replace a line in a .txt file.

The .txt file always has different number at the end of the line.

For example:

...............................txt (first)....................................
appversion= 10.10.1
............................txt (a second time)................................
appversion= 10.10.2
...............................txt (third)...................................
appversion= 10.10.5

---

I need to replace appversion + number behind it (the number is always different). I have set the required value in variable.

How do I do this?

• Richard: Are you wanting to replace all appversion= 10.10.X with the same thing?

Answer 1

Part of this issue you are getting, which I see from your comments, is that you are trying to replace text in a file and saved it back to the same file while you are still reading it.

I will try to show a similar solution while addressing this. Again we are going to use -replaces functionality as an array operator.

$NewVersion = "Awesome"
$filecontent = Get-Content C:\temp\file.txt
$filecontent -replace '(^appversion=.*\.).*',"`1ドル$NewVersion" | Set-Content C:\temp\file.txt 

This regex will match lines starting with "appversion=" and everything up until the last period. Since we are storing the text in memory we can write it back to the same file. Change $NewVersion to a number ... unless that is your versioning structure.

Not sure about what numbers you are keeping

About which part of the numbers, if any, you are trying to preserve. If you intend to change the whole number then you can just .*\. to a space. That way you ignore everything after the equal sign.

Answer 2

Yes, you can with regex. Let call $myString and $verNumber the variables with text and version number

$myString = "appversion= 10.10.1";
$verNumber = 7;

You can use -replace operator to get the version part and replace only last subversion number this way

$mystring -replace 'appversion= (\d+).(\d+).(\d+)', "appversion= `1ドル.`2ドル.$verNumber";

• charles: (gc c:\test.txt) -replace 'appversion=(/d)',"appversion= $FolderName" | Set-content c:\test.txt
• Naigel: Is gc c:\test.txt returning you a string or an object?
• Naigel: so you should get the text, try gc c:\test.txt -raw I suggest you to split your code, instead of using pipe save each step in a variable and check step by step what is wrong