# Select files
$files = gci . -recurse | ? { ($_ -match "txt$") -and ((gc $_.VersionInfo.FileName) -match "the_sink") } | % { $_.VersionInfo.FileName }

# Back'em up, just in case:
$files | % { cp $_ "$($_).bak" }

# Replace
$files | %{ (gc $_) -replace "foo","bar" | sc -Path $_ }

# Select files
$files = gci . -recurse | ? { ($_ -match "txt$") -and ((gc $_\.VersionInfo.FileName) -match "the_sink") } | % { $_.VersionInfo.FileName }

# Back'em up, just in case:
$files | % { cp $_ "$($_).bak" }

# Replace
$files | %{ (gc $_) -replace "foo","bar" | sc -Path $_ }

# Select files
$files = gci . -recurse | ? { ($_ -match "txt$") -and ((gc $_.VersionInfo.FileName) -match "the_sink") } | % { $_.VersionInfo.FileName }

# Back'em up, just in case:
$files | % { cp $_ "$($_).bak" }

# Replace
$files | %{ (gc $_) -replace "foo","bar" | sc -Path $_ }

# Select files
$files = Select-String -Path .\**\*.txt -Pattern "foo" | % { $_.Path } | Get-Unique

# Back'em up, just in case:
$files | % { Copy-Item $_ "$($_).bak" }

# Replace
$files | %{ (Get-Content $_) -replace "foo","bar" | Set-Content -Path $_ }

replace foo -> bar in all .txt files down the tree

Dunno why, the syntax highlighter adds \3's to the code. Try plain text.

Search and Replace regexp in subdirectories

regex, search, replace, regexp

Windows PowerShell