Using -replace on pipes in powershell

This should do the trick, it'll go through all the lines in the file, and replace any "a" with "b", but you'll need to save that back into a file afterwards

cat file | % {$_.replace("a","b")} | out-file newfile

To use the Powershell -replace operator (which works with regular expressions) do this:

cat file.txt | % {$_ -replace "\W", ""} # -replace operator uses regex

note that the -replace operator uses regex matching, whereas the following example would use a non-regex text find and replace, as it uses the String.Replace method of the .NET Framework

cat file | % {$_.replace("abc","def")} # string.Replace uses text matching