{"id":6612,"date":"2019-03-29T10:03:36","date_gmt":"2019-03-29T14:03:36","guid":{"rendered":"https:\/\/jdhitsolutions.com\/blog\/?p=6612"},"modified":"2019-03-29T10:03:42","modified_gmt":"2019-03-29T14:03:42","slug":"more-fun-with-docker-containers-and-powershell","status":"publish","type":"post","link":"https:\/\/jdhitsolutions.com\/blog\/powershell\/6612\/more-fun-with-docker-containers-and-powershell\/","title":{"rendered":"More Fun with Docker Containers and PowerShell"},"content":{"rendered":"

A few days ago I shared some experiences of working with Docker containers and PowerShell<\/a>. As I continue to learn Docker, I am also learning how to manage it with PowerShell. The Docker command line tools are fine but I think they are even better when drizzled with a nice PowerShell glaze. Here's a bit more of what I have been working on.<\/p>\n

<\/p>\n

Container ID<\/h2>\n

In my previous work, I needed the full container ID so I could use it with the PowerShell PSSession cmdlets. Thanks to people like Tim Pringle, who provided tips on better using the Docker CLI, specifically the filter option.<\/p>\n

docker container ls -f Name=srv4\n<\/pre>\n
The -f could also be written as --filter.<\/p>\n
\"filtering<\/a><\/p>\n
Be careful. Container names are case-sensitive.<\/p>\n
With this, I can combine it with a few other parameters to get the full configuration ID.<\/p>\n
docker container ls --no-trunc -qf Name=srv4\n<\/pre>\n
\"getting<\/a><\/p>\n
Formatting Containers<\/h2>\n
It gets better. After a bit of research and experimentation, I figured out how to take advantage of the --format parameter in the Docker CLI.\u00a0 This is meant to show you what formatting options are available to you using the JSON format.<\/p>\n
docker container ls --no-trunc --format \"{{json .}}\"\n<\/pre>\n
\"Docker<\/a><\/p>\n
You can format using any heading preceded by a colon. In other words, you can tell Docker what properties to return from the JSON output.<\/p>\n
docker container ls -a --no-trunc --format \"{{json .Names}},{{json .ID}},{{json .Image}},{{json .Networks}},{{json .Mounts}},{{json .CreatedAt}}\"\n<\/pre>\n
\"Selected<\/a><\/p>\n
Hey! That is a CSV output. I can use PowerShell to turn that into objects.<\/p>\n
docker container ls -a --no-trunc --format \"{{json .Names}},{{json .ID}},{{json .Image}},{{json .Networks}},{{json .Mounts}},{{json .CreatedAt}}\" |\nConvertFrom-CSV -Header \"Name\",\"ID\",\"Image\",\"Network\",\"Mounts\",\"Created\"<\/pre>\n
\"Docker<\/a><\/p>\n
That is very useful, so why not take everything? I know Docker will provide JSON output which means I can convert it and then tweak a few properties to be the of the proper type.<\/p>\n
docker container ls -a --no-trunc --format \"{{json .}}\" | convertfrom-json |\nSelect-Object ID,@{Name=\"Name\";Expression = {$_.names}},Image,\n@{Name=\"Created\";Expression = {($_.createdat -split \"\\s[-+]\\d{4}.*\")[0] -as [datetime]}},\nNetworks,Mounts\n<\/pre>\n
\"Docker<\/a><\/p>\n
In case you're wondering I'm using a regular expression pattern to parse the CreatedAt value to that I can convert it to a proper DateTime object.<\/p>\n
Digging Deeper<\/h2>\n
You know me. I always want to discover how far I can go. The Docker CLI has an option to inspect a container. This allows you to get all the information about a given container. The default output is a JSON document. This means I can get all container names and then inspect each one, converting the JSON output to objects in PowerShell.<\/p>\n
$c = docker container ls -a --no-trunc --format \"{{json .Names}}\" | \nforeach-object { docker container inspect $_ | ConvertFrom-Json }\n<\/pre>\n
I get output like this:<\/p>\n
\"Sample<\/a><\/p>\n
With a bit of scripting, I can turn this into something a bit more manageable.<\/p>\n
foreach ($item in $c) {\n    $item | Select-object Id,\n    @{Name=\"Name\";Expression = {$_.Name.substring(1)}},\n    @{Name=\"State\";Expression = {$_.state.status}},\n    @{Name=\"IsRunning\";Expression = {$_.state.Running}},\n    @{Name=\"Started\";Expression = {$_.state.startedat -as [datetime]}},\n    @{Name=\"Finished\";Expression = {\n       #this value shows the last time it finished which won't be accurate if\n       #the container is running\n       if ($_.state.running) {\n          $null\n       }\n       else {\n     $_.state.finishedat -as [datetime]\n     }\n     }},\n    @{Name=\"Runtime\";Expression = { \n    if ($_.state.running) { \n     (Get-Date) - ($_.state.startedat -as [datetime])\n    } \n    else {\n        ($_.state.finishedat -as [datetime]) - ($_.state.startedat -as [datetime])\n    }\n    }},\n    Platform,Mounts,\n    @{Name=\"Image\";Expression = { (docker image inspect ($_.image -split \":\")[1] --format \"{{json .RepoTags}}\") -replace '\\[|\\]|\"',\"\" }},\n    @{Name=\"Created\";Expression ={$_.Created -as [datetime]}}\n}\n<\/pre>\n
I can even add my own properties.<\/p>\n
\"my<\/a><\/p>\n
Toolmaking Time<\/h2>\n
Obviously, nobody wants to type that all the time. So I turned the code into a proper PowerShell function.<\/p>\n