Find and Replace in a Large File

Question

I want to find a piece of text in a large xml file and want to replace with some other text. The size of the file is around ( 50GB). I want to do this in command line. I am look

Answer 1

It does not like it because you can't read from a file and write back to it at the same time using Get-Content/Set-Content. I recommend using a temp file and then at the end, rename file1.xml to file1.xml.bak and rename the temp file to file1.xml.

1. Yes as long as you don't try to load the whole file at once. Line-by-line will work but is going to be a bit slow. Use the -ReadCount parameter and set it to 1000 to improve performance.
2. Which command line? PowerShell? If so then you can invoke your script like so .\myscript.ps1 and if it takes parameters then c:\users\joe\myscript.ps1 c:\temp\file1.xml.

3. In general for regexes I would use single quotes if you don't need to reference PowerShell variables. Then you only need to worry about regex escaping and not PowerShell escaping as well. If you need to use double-quotes then the back-tick character is the escape char in double-quotes e.g. "`$p1 is set to $ps1". In your example single quoting simplifies your regex to (note: forward slashes aren't metacharacters in regex):

   'xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"'

4. Absolutely you want to stream this since 50GB won't fit into memory. However, this poses an issue if you process line-by-line. What if the text you want to replace is split across multiple lines?

5. If you don't have the split line issue then I think PowerShell can handle this.