Background job information

[HasEveryUsernameBeenTaken]

Would it be possible to display the number of active background jobs in a segment or include this in an existing segment?

I think I first saw this kind of thing in Liquid Prompt on GNU/Linux. In PowerShell, I previously included the following in a custom prompt function, and I miss it in Oh My Posh.

[int] $BackgroundJobs = (Get-Job -State Running).Count
[int] $StoppedJobs = (Get-Job | Where-Object { 'Stopped','Stopping' -iContains $PSItem.State}).Count

…

If ($BackgroundJobs -gt 0) {
	Write-Host -NoNewline "${BackgroundJobs}& "
}
If ($StoppedJobs -gt 0) {
	Write-Host -NoNewline "${StoppedJobs}z "
}

[JanDeDobbeleer]

You can add this by leveraging the text segment. You can create a function to store the value in an environment variable:

function Set-EnvVar {
    $env:BG_JOBS = (Get-Job -State Running).Count
}
New-Alias -Name 'Set-PoshContext' -Value 'Set-EnvVar' -Scope Global -Force

then add the following to your config:

{
  "type": "text",
  "style": "powerline",
  "powerline_symbol": "\uE0B0",
  "foreground": "#ffffff",
  "background": "#0077c2",
  "properties": {
    "template": "{{if ne .Env.BG_JOBS \"0\" }}{{ .Env.BG_JOBS }}{{ end }}"
  }
}

[JanDeDobbeleer]

@MattKotsenas depends how long this cmdlet takes to execute. Otherwise it's a bad idea to add that in the core as this can't be measured with oh-my-posh debug.

[MattKotsenas]

Get-Job appears to be reasonably fast (at least for me; Surface Book 3 from 2020 @ 2.0 GHz):

@(1..10) | %{ Measure-Command -Expression { Get-Job } } | %{ $_.TotalMilliseconds } | measure-object -Average

Count             : 10
Average           : 0.26698
Sum               :
Maximum           :
Minimum           :
StandardDeviation :
Property          :

A more realistic measure of the full end-to-end cost:

With 0 jobs

@(1..10) | %{ measure-command { $jobs = (Get-Job); $running = ($jobs | ?{ $_.State -eq "Running" }); $finished = ($jobs.Count - $running.Count); } } | %{ $_.TotalMilliseconds } | measure-object -average

Count             : 10
Average           : 1.91483
Sum               :
Maximum           :
Minimum           :
StandardDeviation :
Property          :

With 500 jobs

@(1..10) | %{ measure-command { $jobs = (Get-Job); $running = ($jobs | ?{ $_.State -eq "Running" }); $finished = ($jobs.Count - $running.Count); } } | %{ $_.TotalMilliseconds } | measure-object -average

Count             : 10
Average           : 15.13528
Sum               :
Maximum           :
Minimum           :
StandardDeviation :
Property          :

Bash shows a similar time:

start=`date +%s%N`; jobs -l ; end=`date +%s%N`; echo Execution time was $((($end - $start)/1000000)) milliseconds.
Execution time was 4 milliseconds.

For some context / comparison, on this machine if I get the value of prompt, comment out the call to Set-PoshContext as well as oh-my-posh itself, I get 4 - 5 milliseconds from Measure-Command.

That feels to me like a small enough cost to be tolerable (assuming sufficient interest). What else should I be considering?

Also, since I'm new to omp internals, is the rationale for not being able to measure it with debug because in order to get the user's session info, it would need to be part of prompt and not inside the omp Go code? Or in other words, users would pay for the jobs call even if they weren't using the segment?

[JanDeDobbeleer]

Decided not to do this as it does add load time on other shells.

[MattKotsenas]

Ok, fair enough. Thanks for updating the thread & letting me know!

[JanDeDobbeleer]

@MattKotsenas on second thought. I'm going to see if I can add it but toggle only when used.

[akelge]

A note about zsh (as I just fought to have it working)

  - type: text
    style: plain
    foreground: green
    properties:
      prefix: ""
      postfix: ""
      text: "$([ $(jobs|wc -l|xargs) -gt 0 ] && echo '\u2622 ')"

Here is how to do it in zsh, you can't use command segment, because it is executed in a subshell that does not know about BG jobs, but the above is executed inline and works

[JanDeDobbeleer]

You can reuse the same logic as indicated above using set_poshcontext in zsh:

function set_poshcontext() {
    export BG_JOBS=$(jobs|wc -l|xargs)
}