A template engine that allows you to have powershell expressions in your templates is a very powerful thing: http://weblogs.asp.net/soever/archive/2006/12/31/a-templating-engine-using-powershell-expressions.aspx
Example Input:
Multi Line Expression:
[[ get-date
1..20
]]
Define function [[ function get-theanswer {42;} ]]
Single Line: [[ theanswer ]]
EOF
Example Output:
Multi Line Expression:
03/14/2007 22:38:09 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Define function
Single Line: 42
EOF
The implementation uses dynamic code generation to build an assembly in order to have a delegate to pass to regex.replace.
Using code generation felt a bit over complicated, and I wondered if it could be simpler.
Some thinking and tinkering later, I arrived at a working implementation.
Getting the multiline regex expression working correctly caused me some difficulty; as it only seems to correctly handle \R as a line separator.
I also added the ability to pipe text to the script, since I like to use the syntax: gc file.txt | expand-template
Now as with any powerful tool you'll need to be careful, and be sure that you fully trust the template file (other wise you'll be vulnerable to a code injection attack)
Expand-Template.ps1:
param ($text="",$BeginTag='[[',$EndTag=']]')
$begintag = [regex]::escape($begintag)
$endtag = [regex]::escape($endtag)
$output=""
$input | %{$text+=[string]$_ + "`r"}
while ($text -match "(?m)(?<pre>.*?)$begintag(?<exp>.*?)$endtag(?<post>.*)") {
$text = $matches.post
$output += $matches.pre
$output += invoke-expression $matches.exp
}
$output += $text
$output -replace "`r", [environment]::newline
