Fetch line starting with a specific string in powershell

Question

I am executing a command for which I am getting output like below

Identifier:  3    SFP
Connector:   7    LC
Transceiver: 7004404000000000 4,8,16_Gbps M5 sw Short_dist
Encoding:    6    64B66B 
Baud Rate:   140  (units 100 megabaud)
Length 9u:   0    (units km)
Length 9u:   0    (units 100 meters)
Length 50u (OM2):  3    (units 10 meters)
Length 50u (OM3):  10   (units 10 meters)
Length 62.5u:0    (units 10 meters)
Length Cu:   0    (units 1 meter)       
Vendor OUI:  00:05:1e
Vendor PN:   57-0000088-01   
Vendor Rev:  A   
Wavelength:  850  (units nm)
Options:     003a Loss_of_Sig,Tx_Fault,Tx_Disable
BR Max:      0   
BR Min:      0   
Date Code:   180316  
DD Type:     0x68
Enh Options: 0xfa
Status/Ctrl: 0xb2
Pwr On Time: 3.52 years (30822 hours)
E-Wrap Control: 0
O-Wrap Control: 0
Alarm flags[0,1] = 0x5, 0x40
Warn Flags[0,1] = 0x5, 0x40
Temperature: 32      Centigrade 
Current:     8.082   mAmps 
Voltage:     3311.6  mVolts 
RX Power:    -5.5    dBm (280.4uW) 
TX Power:    -2.8    dBm (523.1 uW)

I need to fetch the last 2 lines only, that is starting with RX and TX out of it.

I was trying like

#$streamOut | Select-String -Pattern "^RX" | select -ExpandProperty line
$streamOut | Select-String -Pattern "RX" | select -ExpandProperty line

This is by code

$session = New-SSHSession -ComputerName $SAN_IP -Credential $cred
$Strem = New-SSHShellStream -SSHSession $Session
$streamOut=@()
$SystemView = $Strem.WriteLine("sfpshow $port_Num")  
sleep -Seconds 5      
$streamOut = @($Strem.read())
sleep -Seconds 5
$RXTX_Data = @($streamOut | ? { $_ -match "^RX" -or  $_ -match "^TX"})      

$RXTX_Data

When I use the below solution in above code, it is returning blank. the $streamOut is array

PS C:\Windows\system32> $streamOut.GetType()

IsPublic IsSerial Name                                     BaseType                                                                                                      
-------- -------- ----                                     --------                                                                                                      
True     True     Object[]                                 System.Array

But it is returning the entire output.

Please let me know on this

$streamOut | Select-String -Pattern "^(RX|TX)" | Select-Object -ExpandProperty Line works for me, provided that $streamOut is an array of lines, such as from a call to Get-Content. Please add the code where you assign $streamOut. — zett42
– zett42, Commented May 19, 2022 at 9:57
@zett42: I m using Strem to execute the commands and $streamOut is a string. so is there any way to convert that to array or any other approch — Empty Coder
– Empty Coder, Commented May 19, 2022 at 12:03

zett42 · Accepted Answer · 2022-05-19 12:35:39Z

4

As you clarified, the $streamOut variable contains a single, multiline string.

In this case you can use Select-String with -AllMatches like this:

$RXTX_Data = ($streamOut | Select-String -Pattern '(?m)^(RX|TX).*$' -AllMatches).Matches.Value
$RXTX_Data  # Output array of matching lines

Output:

RX Power:    -5.5    dBm (280.4uW)
TX Power:    -2.8    dBm (523.1 uW)

Note that it is important to use the (?m) inline modifier for multiline mode, which changes behaviour of ^ to anchor beginning of line and $ to anchor end of line, instead of beginning and end of whole input string.

An easier alternative is to split the string into lines first, so you can use the -match operator to filter for matching lines:

$streamLines = $streamOut -split '\r?\n'
$RXTX_Data = $streamLines -match '^(RX|TX)'

This works because -match and other comparison operators act as a filter when the LHS operand is a collection like an array. We don't need multiline mode, because the RegEx gets applied to each array element (line) individually.

The above two lines could even be condensed into a one-liner:

$RXTX_Data = ($streamOut -split '\r?\n') -match '^(RX|TX)'

answered May 19, 2022 at 12:35

zett42

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2 Comments

Empty Coder Over a year ago

Thanks for the response. I am getting the data of RX and TX. need one more help. how to get the numeric value out of it. like from RX Power: -5.5 dBm (280.4uW) extract -5.5

zett42 Over a year ago

@EmptyCoder $rxValue = if('RX Power: -5.5 dBm (280.4uW)' -match ':\s*(\S+)') { $matches[1] }

Romylussone · Accepted Answer · 2022-05-19 09:38:29Z

1

try this :

$streamOut = Get-Content -Path "Your_Output_FilePath"
$streamOut | ? { $_ -match "^RX" -or  $_ -match "^TX"}

answered May 19, 2022 at 9:38

Romylussone

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3 Comments

zett42 Over a year ago

Nice! Even shorter one: $streamOut -match '^(RX|TX)'. This works because -match and other comparison operators act as a filter when the LHS operand is an array.

Empty Coder Over a year ago

@Romylussone: one more thing. this solution is working only for object[], not for String.

Empty Coder Over a year ago

@zett42: one more thing. this solution is working only for object[], not for String.

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