powershell regular expressions - regex

Question

quick one:
$logFile="D:\Code\functest\1725.log"
function getTime($pattern) {
Get-Content $logFile | %{ if ($_.Split('\t') -match $pattern) {$_} }
}
getTime("code")
gives me
simple 17-Feb-2011 10:45:27 Updating source code to revision: 49285
simple 17-Feb-2011 10:54:22 Updated source code to revision: 49285
but if I change the print value from
$_
to
$matches
I get nothing. I thought this array should have been created automatically? probably something silly, but this is my first day of using powershell :-)
EDIT: what I want to return is
Get-Date (column 2 of the matching line)

Answer 1

Your call to Split() is using C# conventions to escape the t to specify a tab character. In PowerShell, you use a single backtick e.g. $_.Split("`t"). Also -match is behaving a bit differently on an array like this so have it operate on each individual string like so:
Get-Content $logFile | Foreach {$_.Split("`t")} | Where { $_ -match $pattern }
There's also a sort of hidden trick here with Get-Content where you can get it to split for you:
Get-Content $logFile -del "`t" | Where { $_ -match $pattern }
Update: based on the updated question, try something like this:
gc $logFile | % {$cols = $_.Split("`t"); if ($cols[2] -match $pattern) {$cols[1]}}
Keeping in mind that arrays are 0-based in PowerShell. If the text is already in a DateTime format that PowerShell/.NET understand, you can just cast it to a DateTime like so [DateTime]$cols[1].

Answer 2

The $_.Split('\t') is breaking it.
First, it's breaking on every letter "t", not at tabs.
Second, it return a array that confounds -match.
With the following code:
Get-Content $logFile | %{ if ($_ -match $pattern) { $matches } }
getTime("code") would return:
Name Value
---- -----
0 code
0 code
This would allow to search with regular expressions, as in
$answerArray = getTime("(\t)(\d+)")
$digitsOfSecondResult = $answerArray[1][2]
Write-Output $digitsOfSecondResult
If you just want to print the lines that match the pattern, try:
Get-Content $logFile | %{ if ($_ -match $pattern) { $_} }
To get the date:
function getTime($pattern) {
Get-Content $logFile | %{ if ($_ -match $pattern) { Get-Date $matches[1] } }
}
getTime("`t(.+)`t.*code")
Or:
function getTime($pattern) {
Get-Content $logFile | %{ if ($_ -match "`t(.+)`t.*$pattern") { Get-Date $matches[1] } }
}
getTime("code")