For the uninitiated this looks completely barbaric, but makes a whole lot of sense when you consider that PS is built around an object-based pipeline. 'Select-String' in PS doesn't actually return a string, but a 'MatchInfo' object, which contains more properties -- 'linenumber', 'context', etc, as well as the 'line' property which contains the actual matched lines as strings. The default output from any part of the pipeline is a human-readable/terminal-display-compatible representation of the object's commonly used properties, thus the truncation.

As an aside, you can replace the foreach with select-object for an efficiency gain:

    sls "Pattern" file.txt | select -exp line | out-file t.txt

You also don't technically need to go through Select-String if all you care about is the line itself:

    (gc file.txt) -match "Pattern" | Out-File t.txt

Comparison operators that get an array as their left argument return the items where the comparison returns true.

Today, I learned "Heath Robinson" is British English for "Rube Goldberg"

http://en.wikipedia.org/wiki/W._Heath_Robinson

You could also use either of these:

  (Select-String "pattern" -Path file.txt).Line > t.txt
  Select-String "Pattern" -Path file.txt | Select-Object -ExpandProperty Line > t.txt

Or equivalent to the second example but with shortcuts:

  sls pattern -path file.txt | select -exp line > t.txt