microsoft page 7 - Dave's Blog

Tab Expansion in PowerShell

PowerShell gives us a real CLI for Windows based around .Net stuff. I don't like the creation of a new shell language but I suppose it makes sense given that they want something C# like but not C# exactly since that's much to verbose and strict for a CLI. One of the functions you can override is the TabExpansion function which is used when you tab complete commands. I really like this and so I've added on to the standard implementation to support replacing a variable name with its value, tab completion of available commands, previous command history, and drive names (there not restricted to just one letter in PS).

Learning the new language was a bit of a chore but MSDN helped. A couple of things to note, a statement that has a return value that you don't do anything with is implicitly the return value for the current function. That's why there's no explicit return's in my TabExpansion function. Also, if you're TabExpansion function fails or returns nothing then the builtin TabExpansion function runs which does just filenames. This is why you can see that the standard TabExpansion function doesn't handle normal filenames: it does extra stuff (like method and property completion on variables that represent .Net objects) but if there's no fancy extra stuff to be done it lets the builtin one take a crack.

Here's my TabExpansion function. Probably has bugs, so watch out!

function EscapePath([string] $path, [string] $original)
{
    if ($path.Contains(' ') -and !$original.Contains(' '))
    {
        '"'   $path   '"';
    }
    else
    {
        $path;
    }
}

function PathRelativeTo($pathDest, $pathCurrent)
{
    if ($pathDest.PSParentPath.ToString().EndsWith($pathCurrent.Path))
    {
        '.\'   $pathDest.name;
    }
    else
    {
        $pathDest.FullName;
    }
}

#  This is the default function to use for tab expansion. It handles simple
# member expansion on variables, variable name expansion and parameter completion
# on commands. It doesn't understand strings so strings containing ; | ( or { may
# cause expansion to fail.

function TabExpansion($line, $lastWord)
{
    switch -regex ($lastWord)
    {
         # Handle property and method expansion...
         '(^.*)(\$(\w|\.) )\.(\w*)$' {
             $method = [Management.Automation.PSMemberTypes] `
                 'Method,CodeMethod,ScriptMethod,ParameterizedProperty'
             $base = $matches[1]
             $expression = $matches[2]
             Invoke-Expression ('$val='   $expression)
             $pat = $matches[4]   '*'
             Get-Member -inputobject $val $pat | sort membertype,name |
                 where { $_.name -notmatch '^[gs]et_'} |
                 foreach {
                     if ($_.MemberType -band $method)
                     {
                         # Return a method...
                         $base   $expression   '.'   $_.name   '('
                     }
                     else {
                         # Return a property...
                         $base   $expression   '.'   $_.name
                     }
                 }
             break;
          }

         # Handle variable name expansion...
         '(^.*\$)([\w\:]*)$' {
             $prefix = $matches[1]
             $varName = $matches[2]
             foreach ($v in Get-Childitem ('variable:'   $varName   '*'))
             {
                 if ($v.name -eq $varName)
                 {
                     $v.value
                 }
                 else
                 {
                    $prefix   $v.name
                 }
             }
             break;
         }

         # Do completion on parameters...
         '^-([\w0-9]*)' {
             $pat = $matches[1]   '*'

             # extract the command name from the string
             # first split the string into statements and pipeline elements
             # This doesn't handle strings however.
             $cmdlet = [regex]::Split($line, '[|;]')[-1]

             #  Extract the trailing unclosed block e.g. ls | foreach { cp
             if ($cmdlet -match '\{([^\{\}]*)$')
             {
                 $cmdlet = $matches[1]
             }

             # Extract the longest unclosed parenthetical expression...
             if ($cmdlet -match '\(([^()]*)$')
             {
                 $cmdlet = $matches[1]
             }

             # take the first space separated token of the remaining string
             # as the command to look up. Trim any leading or trailing spaces
             # so you don't get leading empty elements.
             $cmdlet = $cmdlet.Trim().Split()[0]

             # now get the info object for it...
             $cmdlet = @(Get-Command -type 'cmdlet,alias' $cmdlet)[0]

             # loop resolving aliases...
             while ($cmdlet.CommandType -eq 'alias') {
                 $cmdlet = @(Get-Command -type 'cmdlet,alias' $cmdlet.Definition)[0]
             }

             # expand the parameter sets and emit the matching elements
             foreach ($n in $cmdlet.ParameterSets | Select-Object -expand parameters)
             {
                 $n = $n.name
                 if ($n -like $pat) { '-'   $n }
             }
             break;
         }

         default {
             $varNameStar = $lastWord   '*';

             foreach ($n in @(Get-Childitem $varNameStar))
             {
                 $name = PathRelativeTo ($n) ($PWD);

                 if ($n.PSIsContainer)
                 {
                     EscapePath ($name   '\') ($lastWord);
                 }
                 else
                 {
                     EscapePath ($name) ($lastWord);
                 }
             }

             if (!$varNameStar.Contains('\'))
             {
                foreach ($n in @(Get-Command $varNameStar))
                {
                    if ($n.CommandType.ToString().Equals('Application'))
                    {
                       foreach ($ext in @((cat Env:PathExt).Split(';')))
                       {
                          if ($n.Path.ToString().ToLower().EndsWith(($ext).ToString().ToLower()))
                          {
                              EscapePath($n.Path) ($lastWord);
                          }
                       }
                    }
                    else
                    {
                        EscapePath($n.Name) ($lastWord);
                    }
                }

                foreach ($n in @(Get-psdrive $varNameStar))
                {
                    EscapePath($n.name   ":") ($lastWord);
                }
             }

             foreach ($n in @(Get-History))
             {
                 if ($n.CommandLine.StartsWith($line) -and $n.CommandLine -ne $line)
                 {
                     $lastWord   $n.CommandLine.Substring($line.Length);
                 }
             }

             # Add the original string to the end of the expansion list.
             $lastWord;

             break;
         }
    }
}

Halloween and Gas Park Weekend

The weekend before last Sarah and I went down to Gas Works Park in Seattle. Gas Works Park is a former Seattle Gas Light Company gasification plant now turned into a park with the machinery kept intact and found right on the shore of Lake Union. There's a large hill right next to the plant with an embedded art installation from which you get an excellent view of the park and the lake. Anyway a very cool place. Afer, we ate at Julia's of Wallingford where I stereotypically had the Santa Cruz omelet. Good food, nice place, nice neighborhood.

This past weekend was Halloween weekend. On Halloween at Microsoft parents bring their kids around the office buildings and collect candy from those who have candy in their office. See Matt's photo of one such hallway at Microsoft. The next day Sarah and I went to two birthday parties the second of which required costume. I went as House (from the television show House) by putting on a suit jacket and carrying a cane. Sarah wore scrubs to lend cred. to my lazy costume. Oh yeah and on Sunday Sarah bought a new car.

Investigation of a Few Application Protocols (Updated)

Windows allows for application protocols in which, through the registry, you specify a URL scheme and a command line to have that URL passed to your application. Its an easy way to hook a webbrowser up to your application. Anyone can read the doc above and then walk through the registry and pick out the application protocols but just from that info you can't tell what the application expects these URLs to look like. I did a bit of research on some of the application protocols I've seen which is listed below. Good places to look for information on URI schemes: Wikipedia URI scheme, and ESW Wiki UriSchemes.

Weekend Dinners: Old friends, Old library

Last Thursday I saw a bunch of college friends that I hadn't seen in a while, despite all of us working at Microsoft, and Saul and Ciera who were visiting. We had dinner at Typhoon! which I haven't been to in quite a while. Daniil and Val brought their cute child. I got to see Charlie and Matt who I'm not sure I've seen since my 25th birthday. There was much nerdiness. I need to remember to organize such a night myself sometime in near future so I don't have to wait another year to see them.

On the weekend Sarah and I went out to dinner at Carnegie's, a former public library in Ballard, Seattle that's now a restaurant. I saw the restaurant's website in Matt's delicious links and thought it looked interesting. The exterior and entryway look like a public library, but just inside its redone as a sort of modern version of french classical with a bar and two dining rooms. No pictures since my replacement camera only arrived today, but there are photos available. They serve french cuisine which was good and not as expensive as I would have expected. An interesting place, although its a bit of a drive and I'm not sure if we'll be going back soon.

Xbox Achievements for Everyday Life

I just upgraded to the Zune 3.0 software which includes games and purchasing music on the Zune via WiFi and once again I'm thrilled that the new firmware is available for old Zunes like mine. Rooting around looking at the new features I noticed Zune Badges for the first time. They're like Xbox Achievements, for example I have a Pixies Silver Artist Power Listener award for listening to the Pixies over 1000 times. I know its ridiculous but I like it, and now I want achievements for everything.

Achievements everywhere would require more developments in self-tracking. Self-trackers, folks who keep statistics on exactly when and what they eat, when and how much they exercise, anything one may track about one's self, were the topic of a Kevin Kelly Quantified Self blog post (also check out Cory Doctorow's SF short story The Things that Make Me Weak and Strange Get Engineered Away featuring a colony of self-trackers). For someone like me with a medium length attention span the data collection needs to be completely automatic or I will lose interest and stop collecting within a week. For instance, Nike iPod shoes that keep track of how many steps the wearer takes. I'll also need software to analyze, display, and share this data on a website like Mycrocosm. I don't want to have to spend extreme amounts of time to create something as wonderful as the Feltron Report (check out his statistic on how many daily measurements he takes for the report). Once we have the data we can give out achievements for everything!

Achievements for Everyday Life

	Carnivore Eat at least ten different kinds of animals.
	Make Friends Meet at least 10% of the residents in your home town.
	Globetrotter Visit a city in every country.
	You're Old Survive at least 80 years of life.

Of course none of the above is practical yet, but how about Delicious achievements based on the public Delicious feeds? That should be doable...