Cycling through multiple variables in for loop

Question

I just started working with Powershell and this is my first script.

I am checking for 3 strings in last 50 lines of a log file. I need to find all three strings and print error message if any one of those is missing. I have written following script but it does not give me the expected results.

(Get-Content C:\foo\bar.log )[-1..-50] | Out-File C:\boom\shiva\log.txt
$PO1 = Get-Content C:\boom\shiva\log.txt | where {$_ -match "<Ping:AD_P01_RCV> ok"}
$PO2 = Get-Content C:\boom\shiva\log.txt | where {$_ -match "<Ping:AD_P02_SND> ok"}
$PO3 = Get-Content C:\boom\shiva\log.txt | where {$_ -match "<Ping:AD_P03_RCV> ok"}

I am satisfied with above piece of code. The problem is with the below. I dont want to use if-else thrice. I am struggling to draft a for loop which can save space and still give me the same result.

if (!$PO1)
{
    "PO1 is critical"
}
else
{
    "PO1 is OK"
}
if (!$PO2)
{
    "PO2 is critical"
}
else
{
    "PO2 is OK"
}
if (!$PO3)
{
    "PO3 is critical"
}
else
{
    "PO3 is OK"
}

Can someone gave me small example of how i can fit these 3 if-else in one for loop.

score 4 · Accepted Answer · 2018-07-16 08:20:54Z

4

If you only want to find out that all 3 strings are present this script will also show which one is missing.
(binary encoded in the variable $Cnt)

## Q:\Test\2018\07\13\SO_51323760.ps1
##
$Last50 = Get-Content 'C:\foo\bar.log' | Select-Object -Last 50
$Cnt = 0

if ($Last50 -match "<Ping:AD_P01_RCV> ok"){$Cnt++}
if ($Last50 -match "<Ping:AD_P02_SND> ok"){$Cnt+=2}
if ($Last50 -match "<Ping:AD_P03_RCV> ok"){$Cnt+=4}

if ($cnt -eq 7){
   "did find all 3 strings "
} else {
   "didn't find all 3 strings ({0})" -f $cnt
}

Variant immediately complaining missing P0(1..3)

$Last50 = Get-Content 'C:\foo\bar.log' | Select-Object -Last 50

if (!($Last50 -match "<Ping:AD_P01_RCV> ok")) {"PO1 is critical"}
if (!($Last50 -match "<Ping:AD_P02_SND> ok")) {"PO2 is critical"}
if (!($Last50 -match "<Ping:AD_P03_RCV> ok")) {"PO3 is critical"}

Sorry I'm a bit slow this monday.

To check in a loop different variables by building the variable name:

1..3| ForEach-Object {
  If (!(Get-Variable -name "P0$_").Value){"`$P0$_ is critical"}
}

edited Jul 16, 2018 at 8:20

answered Jul 13, 2018 at 11:59

user6811411

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4 Comments

data-bite Over a year ago

Hi Lot. Thanks for this solution however i want to identify which one is missing as well. Also for some reason i get result "didn't find all 3 strings" even though all 3 strings are present.

user6811411 Over a year ago

What number was trailing the message? Testing locally with your above output works correct returning (5) when I remove the line with snd.

data-bite Over a year ago

my apologies Lot... got 'did find all 3 strings' output... Can you suggest how i can point out if any individual string (PO1 / PO2 / PO3) is missing... Also it would be fantastic if you could tell me how i can loop the 3 variables in a for loop as my original question...

user6811411 Over a year ago

I appended another script which checks in a loop which variable is empty

Ansgar Wiechers · Accepted Answer · 2018-07-13 12:15:28Z

1

What you're trying to do is better addressed with a hashtable than with individually named variables.

$data = Get-Content 'C:\boom\shiva\log.txt'

$ht = @{}
1..3 | ForEach-Object {
    $key = 'P{0:d2}' -f $_
    $str = if ($_ -eq 2) {"${key}_SND"} else {"${key}_RCV"}
    $ht[$key] = $data -match "<ing:AD_${str}> ok"
}

$ht.Keys | ForEach-Object {
    if ($ht[$_]) {
        "${key} found in log."
    } else {
        "${key} not found in log."
    }
}

You can check if all lines were present at least once with something like this:

if (($ht.Values | Where-Object { $_ }).Count -lt 3) {
    'Line missing from log.'
}

edited Jul 13, 2018 at 12:15

answered Jul 13, 2018 at 12:06

Ansgar Wiechers

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Comments

mklement0 · Accepted Answer · 2018-07-14 02:59:25Z

0

PSv3 introduced the -Tail (-Last) parameter to Get-Content, which is the most efficient way to extract a fixe number of lines from the end of a file.

You can pipe its output to Select-String, which accepts an array of regex patterns, any of which produces a match (implicit OR logic).

$matchingLines = Get-Content -Tail 50 C:\foo\bar.log |
  Select-String '<Ping:AD_P01_RCV> ok', '<Ping:AD_P02_SND> ok', '<Ping:AD_P03_RCV> ok'

if ($matchingLines) { # at least 1 of the regexes matched
   $matchingLines.Line  # output the matching lines
} else {  # nothing matched
  Write-Warning "Nothing matched."
}

answered Jul 14, 2018 at 2:59

mklement0

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Comments

data-bite · Accepted Answer · 2018-07-16 11:00:11Z

I finally got below draft that resolved my query to cycle variables through a for loop. I finally had to convert those individual variables to a array. But htis gives me expected result. Basically i need this script to provide input to my Nagios plugin which needs minor modification but its done.

(Get-Content C:\foo\bar.log )[-1..-50] | Out-File C:\boom\shiva\log.txt
$j = 1
$PO = new-object object[] 3
$PO[0] = Get-Content C:\boom\shiva\log.txt | where {$_ -match "<Ping:AD_P01_RCV> ok"}
$PO[1] = Get-Content C:\boom\shiva\log.txt | where {$_ -match "<Ping:AD_P02_SND> ok"}
$PO[2] = Get-Content C:\boom\shiva\log.txt | where {$_ -match "<Ping:AD_P03_RCV> ok"}
foreach( $i in $PO){
    if (!$i){
        "PO "+$j+" is CRITICAL"}
    else{
        "PO "+$j+" is OK"}
    $j+=1
}

Thank you LotPings, Ansgar and mklement0 for your support and responses. I picked up a few things from your answers.

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