Retrieve content between 2 words - parsing

Question

I have a build log which I want to extract some content from. I want to extract [xxxxcontentxxxx] out of the log file given the system name, if any.
Input.txt:
150755: CMDLINE=omake System1
150758: Subsystem Start: Tue Dec 22 03:33:06 2015 1450726386
[xxxxcontentxxxx]
151251: Subsystem End: Tue Dec 22 03:35:00 2015 1450726500
151255: CMDLINE=omake System2
151258: Subsystem Start: Tue Dec 22 03:35:00 2015 1450726500
151668: Subsystem End: Tue Dec 22 03:36:28 2015 1450726588
151672: CMDLINE=omake System3
151675: Subsystem Start: Tue Dec 22 03:36:29 2015 1450726589
[xxxxcontentxxxx]
152020: Subsystem End: Tue Dec 22 03:38:14 2015 1450726694
152024: CMDLINE=omake System4
152027: Subsystem Start: Tue Dec 22 03:38:15 2015 1450726695
[xxxxcontentxxxx]
152294: Subsystem End: Tue Dec 22 03:39:12 2015 1450726752
152298: CMDLINE=omake System5
152301: Subsystem Start: Tue Dec 22 03:39:12 2015 1450726752
[xxxxcontentxxxx]
152558: Subsystem End: Tue Dec 22 03:40:18 2015 1450726818
For example, I want to extract for System2, System3 and System4. The output should be saved to a file in the following format:
Note: System2 is skipped because it does not contain [xxxxcontentxxxx]
Output.txt:
151672: CMDLINE=omake System3
151675: Subsystem Start: Tue Dec 22 03:36:29 2015 1450726589
[xxxxcontentxxxx]
152020: Subsystem End: Tue Dec 22 03:38:14 2015 1450726694
152024: CMDLINE=omake System4
152027: Subsystem Start: Tue Dec 22 03:38:15 2015 1450726695
[xxxxcontentxxxx]
152294: Subsystem End: Tue Dec 22 03:39:12 2015 1450726752
How can I achieve this with PowerShell?
Here is something I have. Certainly, there is a more elegant way of achieving this:
$reader = [System.IO.File]::OpenText("C:\log.txt")
try {
$startPrinting = $false
for (;;) {
$line = $reader.ReadLine()
if ($line -eq $null) { break }
if ($line.Split(' ').Contains("System2") -or
$line.Split(' ').Contains("System3") -or
$line.Split(' ').Contains("System4")
) {
$startPrinting = $true
}
if ($startPrinting) {
Write-Host $line
}
if ($line.split(' ').Contains('End:')) {
$startPrinting = $false
}
}
} finally {
$reader.Close()
}

Answer 1

You could for instance use a switch statement, like this:
$systems = 'System2', 'System3', 'System4'
$reader = [IO.File]::OpenText('.\Documents\test.txt')
while ($line = $reader.ReadLine()) {
switch -regex ($line) {
'CMDLINE=omake (\S+)' {
$systemName = $matches[1]
$msg = #($line)
}
'Subsystem End' {
if ($systems -contains $systemName) {
if ($msg.Count -gt 3) {
$msg -join "`r`n"
} else {
"Note: $systemName is skipped because it doesn't have content."
}
}
}
default { $msg += $line }
}
}
$reader.Close()
This is, of course, entirely unpolished as it assumes that your input file will always start with a CMDLINE line and end with a Subsystem End line. But it should give you the general idea.