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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘Sh Shell’ Category

Don’t fall for the golden hammer: avoid git empty commits, especially for kicking off parts of your CI/CD

Posted by jpluimers on 2022/08/16

A while back Kristian Köhntopp (isotopp) wrote a blog post after quite a Twitter argument where he poses against using git empty commits. I’m with Kris: don’t use them for anything, especially not for kicking off your CI/CD.

Basically his blog post is all about avoiding to think you have a golden hammer, and avoid falling for the Law of the instrument – Wikipedia.

Originally, Abraham Maslow said in 1966:

“I suppose it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail.”

For me this has all to do with preventing technical debt: find the right tool to kick your CI/CD pipeline after part of that chain somehow malfunctioned is way better than polluting the commit history with empty commits.

His blog post: [Wayback/] Empty commits and other wrong tools for the job | Die wunderbare Welt von Isotopp

The most important bit in it:

And since we are talking about CI/CD pipelines: Don’t YAML them. Don’t JSON them. Don’t XML them.

Programming in any of these three is wrong use of tooling, and you should not do it.

  • YAML, JSON and XML are for declarative things.
  • Python, Go and Rust are for procedural things.
  • Bash is for interactive use only.

Use the proper tooling for the job. Be an engineer.

This very much reminds me of an Entwickler Konferenz keynote a long time ago, where Neal Ford made the point that most software engineers act very much unlike what is expected from traditional engineering way of operating where the engineer is both responsible and liable for his actions.

The start of the Twitter thread: [] Kristian Köhntopp on Twitter: “A lot of people right now that git is an API and triggering CI/CD pipelines with empty commits replaces the equivalent of a Kubernetes controller for their fragile pile of bash in git triggers. This is broken and begets more brokenness. Evidence:… “

The tweet that started the subtweet: [] Florian Haas on Twitter: “(For anyone wondering, what’s nice about this one is it works in any CI. So you don’t have to remember how to manually kick off a GitLab CI pipeline or GitHub Action or Zuul job, you just push an empty commit and off you go.)”

Other relevant tweets:

Yes, you want to avoid shell too (anything like for instance sh, ash, dash, bash or zsh), but you have to know it (and understand why to avoid it) as often it is the only interactive way to access systems from the console.

And of course Kris also wrote a big document on that too, which is available as full PDF (Wayback), full HTML (Wayback) and chaptered HTML Die UNIX Shell /bin/sh.

But more importantly, Kris wrote [Wayback/] Using Python to bash | Die wunderbare Welt von Isotopp which is about using Python to do things you might be tempted to do in the shell. It quotes

Shell is a thing you want to understand and then not use, because you learned to understand it.

which is from the German post in thread [Wayback/] Bashprogrammierung, wo gehts am besten los which quotes Kris’ 1998 message:

From kris Tue Sep 1 11:26:12 1998
From: kris
Newsgroups: de.comp.os.unix.misc
Subject: Re: Shell-Frage, find, xargs, kopieren von vielen Dateien
References: <6seh24$q9a$>
From: (Kristian Koehntopp)
Alignment: chaotic/neutral
X-Copyright: (C) Copyright 1987-1998 Kristian Koehntopp -- All rights
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8bit (Marc Haber) writes:
>mir ist das ganze Zeug mit der Shell, find, xargs und Konsorten noch
>reichlich verschlüsselt.

>xargs hin oder sollte ich besser ein Perlskript schreiben?

Verwende Perl. Shell will man koennen, dann aber nicht verwenden.



Posted in *nix, *nix-tools, ash/dash, ash/dash development, bash, bash, Conference Topics, Conferences, Continuous Integration, Development, DVCS - Distributed Version Control, Event, git, Power User, Scripting, sh, Sh Shell, Software Development, Source Code Management, Technical Debt | Leave a Comment »

checkbashisms(1) – Linux man page

Posted by jpluimers on 2021/11/17

Even with lots of experience, one learns new things every day.

A while ago, I discovered checkbashisms which checks sh shel scripts (usually with extension .sh) scripts to they do not contain code specific to bash.

[Wayback] checkbashisms(1) – Linux man page

checkbashisms, based on one of the checks from the lintian system, performs basic checks on /bin/sh shell scripts for the possible presence of bashisms. It takes the names of the shell scripts on the command line, and outputs warnings if possible bashisms are detected.

Note that the definition of a bashism in this context roughly equates to “a shell feature that is not required to be supported by POSIX”; this means that some issues flagged may be permitted under optional sections of POSIX, such as XSI or User Portability.

In cases where POSIX and Debian Policy disagree, checkbashisms by default allows extensions permitted by Policy but may also provide options for stricter checking.

The source by now is a Perl script (it used to be a bash script) of which you can find the latest version here: [Wayback] scripts/ · master · Debian / devscripts · GitLab

Not installed by default

Virtually no distribution has checkbashisms installed by default.

In fact, the package containing checkbashisms heavily varies by distribution.

For OpenSuSE, it is in a package by itself: [Wayback] openSUSE Software: package checkbashisms


Tool for Checking /bin/sh Scripts for Possible Bashisms

checkbashisms performs basic checks on /bin/sh shell scripts for the possible presence of bashisms. It takes the names of the shell scripts on the command line, and outputs warnings if possible bashisms are detected.


Posted in *nix, *nix-tools, bash, bash, Development, Power User, Scripting, sh, Sh Shell, Software Development | Leave a Comment »

VMware ESXi console: viewing all VMs, suspending and waking them up: part 2

Posted by jpluimers on 2021/04/27

Last week ended up to be a kind of VMware ESXi heavey, and this week will be similar. So it is time for following up on VMware ESXi console: viewing all VMs, suspending and waking them up: part 1.

That one ended with

Then we get this to print some of the capture groups:

vim-cmd vmsvc/getallvms | sed -n -E -e "s/^([[:digit:]]+)\s+((\S.+\S)?)\s+(\[\S+\])\s+(.+\.vmx)\s+(\S+)\s+(vmx-[[:digit:]]+)\s*?((\S.+)?)$/Vmid:\1 Guest:\6 Version:\7 Name:\3 Datastore:\4 File:\5 Annotation:\8/p"

With this output:

Vmid:10 Guest:windows9_64Guest Version:vmx-14 Name:X9SRI-3F-W10P-EN-MEDIA Datastore:[EVO860_500GB] File:VM/X9SRI-3F-W10P-EN-MEDIA/X9SRI-3F-W10P-EN-MEDIA.vmx Annotation:
Vmid:5 Guest:centos64Guest Version:vmx-11 Name:PPB Local_Virtual Machine_v4.0 Datastore:[EVO860_500GB] File:VM/PPB-Local_Virtual-Machine_v4.0/PPB Local_Virtual Machine_v4.0.vmx Annotation:PowerPanel Business software(Local) provides the service which communicates

Figuring out power state for each VM

This will be in the next installment, as by now this already has become a big blog-post (:

I basically went the vim-cmd vmsvc way instead of the esxcli vm way. My motivation was the easier to understand ID values. They are the basis of virtually all vim-cmd vmsvc based commands:

# vim-cmd vmsvc --help
Commands available under vmsvc/:
acquiremksticket                 get.snapshotinfo                 
acquireticket                    get.spaceNeededForConsolidation  
createdummyvm                    get.summary                      
destroy                          get.tasklist                     
device.connection                getallvms                        
device.connusbdev                gethostconstraints               
device.ctlradd                   message                          
device.ctlrremove                power.getstate                   
device.disconnusbdev             power.hibernate                  
device.diskaddexisting           power.on                         
device.diskextend                power.reboot                     
device.diskremove                power.reset                      
device.getdevices                power.shutdown                   
device.nvdimmadd                 power.suspend                    
device.nvdimmremove              power.suspendResume              
device.toolsSyncSet              queryftcompat                    
devices.createnic                reload                           
get.capability                   setscreenres                     
get.config                       snapshot.create                  
get.config.cpuidmask             snapshot.dumpoption              
get.configoption                 snapshot.get                     
get.datastores                   snapshot.remove                  
get.disabledmethods              snapshot.removeall               
get.environment                  snapshot.revert                  
get.filelayout                   snapshot.setoption               
get.filelayoutex                 tools.cancelinstall              
get.guest                        tools.install                    
get.guestheartbeatStatus         tools.upgrade                    
get.managedentitystatus          unregister                       
get.networks                     upgrade                          

My “goto” for getting information is [Wayback] “vim-cmd vmsvc” – Google Search, and a few sample pages are here:

  1. [Wayback] Performing common virtual machine-related tasks with command-line utilities (2012964) (showing that there are many tasks only vim-cmd vmsvc can do, but esxcli vm cannot)
  2. [Wayback] Powering on a virtual machine from the command line when the host cannot be managed using vSphere Client (1038043) (showing how to combine vim-cmd vmsvc/getallvms, vim-cmd vmsvc/power.getstate and vim-cmd vmsvc/power.on)
  3. [Wayback] Determine the power status of a virtual machine on an ESX or ESXi host (1003737) (showing vim-cmd vmsvc/getallvms, vim-cmd vmsvc/power.getstate and ps –auxwww | grep –i VM_NAME)
  4. [Wayback] Collecting information about tasks in VMware ESXi/ESX (1013003) (showing the relation between VMs and tasks using  vim-cmd vimsvc/task_list, vim-cmd vmsvc/getallvms and vim-cmd vimsvc/task_info)
  5. [Wayback] Unable to Power off a Virtual Machine in an ESXi host (1014165) (focussing on vim-cmd vmsvc/getallvms, vim-cmd vmsvc/power.getstate, vim-cmd vmsvc/power.shutdown and vim-cmd vmsvc/
  6. [Wayback] Reloading a vmx file without removing the virtual machine from inventory (1026043) (showing vim-cmd vmsvc/getallvms and vim-cmd vmsvc/reload)
  7. [Wayback] Investigating virtual machine file locks on ESXi hosts (10051) (trying to show how to combine vim-cmd vmsvc/getallvms, grep, awk, find and xargs to find vmdk files, but fails because of parsing errors)

The pattern above is that most of the vim-cmd vmsvc examples are for power state and tasks. Not fully sure why, but my guess is it is what most people use it for. That kind of use what this series of posts also focuses on too, but certainly not the only use. Read the first numbered entry above to get a full grasp of what is possible. I hope to find time in the future to show some more examples outside the power and task realms.

Basically the only time you need to check out esxcli with VMs is when you cannot shut down a VM in a normal way. These links explain what to do in that case:

So let’s go back to basics, and start with getting info on all vim-cmd vmsvc commands.

Help on all vim-cmd vmsvc commands

Executing vim-cmd help vmsvc (preferred) or vim-cmd help vmsvc --help gives you all commands prepended with the line Commands available under vmsvc/:.

Executing vim-cmd help vmsvc/command prints the help for a single command (but vim-cmd help vmsvc/command -help first prints an error, then the help).

Here are the steps how I got the help help for all commands.

First I needed a list of all commands. This is already a multi-stage process, so below the full command I will explain the bits.

vim-cmd help vmsvc | sed '1d' | xargs -n 1 -r echo | sort
  1. vim-cmd help vmsvc gives all the commands (two per line!) prepended by the line Commands available under vmsvc/:.
  2. sed '1d' stripts that line.
  3. xargs -n 1 -r echo does a lot of things:
    1. It parses the sed '1d' input line by line, splits each line into parts, combines all the parts, then executes echo with the combined parts
    2. The -n 1 ensures each invocation of echo takes only a single one of the combined parts
    3. -r is just a protection: if there is no input, then echo is never executed, resulting in empty output
  4. sort will sort all the combined output of all the echo invocations to undo the horizontal combination of parts that xargs did

Now getting the help is doing more of the above, with some more bits to explain:

vim-cmd help vmsvc | sed '1d' | xargs -n 1 -r echo | sort | xargs -n 1 -r -I {} vim-cmd help vmsvc/{}
  1. Normally, xargs will execute each command by appending the parameter inserting a space in front of each parameter
  2. -I {} will force xargs to put each argument just as is in the place where {} is used in the argument
  3. This executes vim-cmd help vmsvc/command in stead of vim-cmd help vmsvc/ command

The result is a long blob of text that is very hard to read as there are no separators between the commands. I saved it as a [Wayback] vim-cmd help for each vmsvc command.txt gist.

With a sh -c shell trick, you can add some more information and separation to the output by embedding :

vim-cmd help vmsvc | sed '1d' | xargs -n 1 -r echo | sort | xargs -n 1 -r -I {} sh -c 'echo "-----" ; echo "help for vim-cmd help vmsvc/{}" ; echo ; vim-cmd help vmsvc/{}'

I have added the output to the [Wayback] delimited vim-cmd help for each vmsvc command.txt gist.

Commands taking a vmid parameter

Now that we know how to output all help, we can filter on it.

An interesting one is to filder only commands taking a vmid parameter:

vim-cmd help vmsvc | sed '1d' | xargs -n 1 -r echo | sort | xargs -n 1 -r -I {} vim-cmd help vmsvc/{} | grep -iw vmid

On VMware ESXi 6.7, this gets you the list:

Usage: acquiremksticket vmid
Usage: acquireticket vmid ticketType
Usage: destroy vmid
Usage: device.connection vmid deviceKey connect
Usage: device.connusbdev vmid usbid
Usage: device.ctlradd vmid ctlr_type bus_number
Usage: device.ctlrremove vmid ctlr_type bus_number
Usage: device.disconnusbdev vmid usbid
Usage: device.diskadd vmid size controller_numer unit_number datastore [ctlr_type]
Usage: device.diskaddexisting vmid disk_file controller_number unit_number [ctlr_type]
Usage: device.diskextend vmid new_size controller_numer unit_number [ctlr_type]
Usage: device.diskremove vmid controller_number unit_number delete_file [controller_type]
Usage: device.getdevices vmid
Usage: device.nvdimmadd vmid size
Usage: device.nvdimmremove vmid deviceKey
Usage: device.toolsSyncSet vmid new state
Usage: devices.createnic vmid adapter-type network-id [network-type]
Usage: get.capability vmid
Usage: get.config vmid
Usage: get.config.cpuidmask vmid
Usage: get.configoption vmid
Usage: get.datastores vmid
Usage: get.disabledmethods vmid
Usage: get.environment vmid
Usage: get.filelayout vmid
Usage: get.filelayoutex vmid
Usage: get.guest vmid
Usage: get.guestheartbeatStatus vmid
Usage: get.managedentitystatus vmid
Usage: get.networks vmid
Usage: get.runtime vmid
Usage: get.snapshotinfo vmid
Usage: get.spaceNeededForConsolidation vmid
Usage: get.summary vmid
Usage: get.tasklist vmid
Usage: message vmid [messageId] [messageChoice]
Usage: power.getstate vmid
Usage: power.hibernate vmid
Usage: vmid
Usage: power.on vmid
Usage: power.reboot vmid
Usage: power.reset vmid
Usage: power.shutdown vmid
Usage: power.suspend vmid
Usage: power.suspendResume vmid
Usage: queryftcompat vmid [faultToleranceType]
Usage: reload vmid
Usage: setscreenres vmid width height
Usage: snapshot.create vmid [snapshotName] [snapshotDescription] [includeMemory] [quiesced]
Usage: snapshot.get vmid
Usage: snapshot.remove vmid snapshotId [removeChildren]
Usage: snapshot.removeall vmid
Usage: snapshot.revert vmid snapshotId suppressPowerOn
Usage: snapshot.setoption [OPTIONS] vmid
Usage: tools.cancelinstall vmid
Usage: tools.install vmid
Usage: tools.upgrade vmid [args]
Usage: unregister vmid
Usage: upgrade vmid [vm_hwversion]

In the above list, the bold entries have to do with power, that is what this series is supposed to center around, so more on that tomorrow.


Posted in *nix, *nix-tools, ash/dash, ash/dash development, Awk, Development, ESXi6, ESXi6.5, ESXi6.7, ESXi7, fgrep, Power User, Scripting, sed, sed script, sh, Sh Shell, Software Development, sort, Virtualization, VMware, VMware ESXi, xargs | Leave a Comment »

ShellCheck – shell script analysis tool

Posted by jpluimers on 2017/03/09

This is golden: ShellCheck – shell script analysis tool.

It checks your shell scripts, either on-line or off-line (brew install shellcheck for Mac, apt, etc for Linuces)


via: regex – Read file line by line with bash script – Stack Overflow

Posted in bash, Development, Scripting, Sh Shell, Software Development | Leave a Comment »

RosettaCode: cool way to improve your coding skills

Posted by jpluimers on 2015/01/22

Wow: I feel like having lived under a stone for 8 years, as RosettaCode has been alive since it was founded in 2007 by Mike Mol.

The idea is that you solve a task and learn from that, or learn by seeing how others have solved tasks or draft tasks.

So in a sense it is similar to the Rosetta stone: it has different languages phrasing the same tasks.

There are already a whole bunch of languages on RosettaCode (of which a few are in the categories below), and you can even suggest or add your own languages.

When you want to solve tasks, be sure to look at the list unimplemented tasks by language that leads to automatic reports by language (for instance two of the languages I use most often: C# and Delphi).

I’m sure there are lots of programming chrestomathy sites, even beyond the ones, and it feels very similar to programming kata sites.


Posted in .NET, APL, Awk, bash, Batch-Files, C, C#, C++, COBOL, CommandLine, Delphi, Development, Fortran, FreePascal, Java, JavaScript/ECMAScript, Lazarus, Object Pascal, Office VBA, Pascal, Perl, PHP, PowerShell, PowerShell, Prism, Scripting, sed script, Sh Shell, Software Development, Turbo Prolog, VB.NET, VBS, VBScript, Visual Studio and tools, Web Development | Leave a Comment »

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