Tcl

⇖_home

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A bootstrap solution for fnest (as platform-independent as possible)

The idea is to either download or detect an installed Tcl interpreter, and then run a Tcl install script for fnest.
Using a minimal Tcl interpreter such as jimsh avoids external dependencies.

The chicken-and-egg problem

It would be easy to run a Tcl install script if a Tcl interpreter is always guaranteed to be present on the local host, but this is not always the case.
So the first problem to be solved is: How to detect the presence of a Tcl interpreter?
Obviously, Tcl can not be used for this task.

The first problem to be solved : Which scripting language/shell command should be used to detect a Tcl interpreter?
Unfortunately, there is no platform-independent solution.
Anyhow, the shell to use could be reduced to:

• Any platform except MS Windows: sh (Bourne shell, or derivates)
• MS Windows: PowerShell

This means that two different install script are required:

1. fnest.sh : For any platform except MS Windows
2. fnest.ps : MS Windows

To run a remote shell script, the shell command is combined with a "download tool".
This "download tool" is also platform-dependent, but may be reduced to:

• wget : Installed by default on most Linux distributions.
• fetch : Installed by default on BSD platforms.
• curl : Installed by default on MacOSX.
• irm/iex : The equivalent commands used on MS Windows.
  
  • irm is short for Invoke-RestMethod. It will download a script from that website.
    
  • iex is short for Invoke-Expression. It will run the script.

The browser as a "OS detection helper"

Modern browsers can detect the local OS, so a web page could show a dynamic content depending on the local OS:

1. Depending on if the detected OS is MS Windows or not, show one "direct download link".
   If the user chooses this option, the script should be downloaded and run "manually" from a shell terminal.
   • https://kuu.se/fossil/fnest.sh
     or
   • https://kuu.se/fossil/fnest.ps
2. An install command, including the "download tool":
   
   • Linux: sh <(wget -q https://kuu.se/fossil/fnest.sh -O -)
   • BSD: sh <(fetch -q https://kuu.se/fossil/fnest.sh)
   • MacOSX: sh <(curl -s https://kuu.se/fossil/fnest.sh)
   • MS Windows: irm https://kuu.se/fossil/fnest.ps | iex

If the local OS cannot be detected, the most logical option is to show the Linux alternative by default.

Example web page

• webpage/index.html
• webpage/index2.html

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Modern browsers can detect the local OS, so a web page could show different install commands depending on the local OS.

Linux (wget)

Image 1: Install using Bash + wget

BSD (fetch)

Image 2: Install using Bash + fetch

MacOSX (curl)

Ms Windows (wget)

irm is short for Invoke-RestMethod . It will download a script from that website.
iex is short for Invoke-Expression . It will run the script.

Linux / Mac / BSD / etc (sh):

Image 1: Browser page for installation using Bash

MS Windows (PowerShell):

Image 2: Browser page for installation using PowerShell

As there only two combinations of the "system download command" and the "system script language", only two download commands and two download are required.

See below for details for each download command.

The preferred way: Use the jimsh0.c source code

As jimsh is tiny (single C-code file, source code: ~614 kB, executable: ~341 kB), it is well suited for bootstrapping over the Net.
If a C compiler is available on the local system, jimsh0.c may be downloaded and compiled.
This is the preferred way to install jimsh0, as no OS detection is required.

Second choice: Use a precompiled jimsh0 executable

If no compiler is available on the local system, the jimsh0 (or jimsh0.exe) executable must be downloaded.
In this case, the OS must be detected first, to download a compatible executable for the local system.

This means that the download server must offer several different jimsh0 binaries, one for each supported OS/platform.
For a generic installation of any software, this may imply a myriad of jimsh0 versions for different platforms, somewhat inconvenient to maintain.
Anyway, in the specific case of fnest, fossil is one dependency, so the list of supported platforms may be the same as the list of platforms on the Fossil download page.

Some assumptions may also be done to further reduce the list of different precompiled jimsh0 executables:

• BSD systems: A compiler is (almost) always present, so there is no need to precompile jimsh for Free|Open|NetBSD.
• Linux systems: Easy to compile and upload to the server, where it also can be tested.
• MS Windows systems: Assume that a compiler is not available, so always offer a precompiled version. (Using MSYS2, this is an easy task.)
• MacOSX, Raspberry Pi: Suggestion: Use a Linux host/VM, and setup a clang cross-compiler environment MacOSX and Raspberry.

Scripting language for the first stage: sh or PowerShell

This is why the very first stage must be written in some "system script language", which is known to always be available on the local system.
As in many other situations, MS Windows is the exception here, so the "system script language" may be resumed to the following:

• Any platform except MS Windows: sh (Bourne shell, or derivates)
• MS Windows: PowerShell

Download command for the first stage: wget, fetch, curl or Invoke-RestMethod/Invoke-Expression

• wget : Installed by default on most Linux distributions.
• fetch : Installed by default on BSD platforms.
• curl : Installed by default on MacOSX.
• Invoke-RestMethod/Invoke-Expression : The equivalent commands used on MS Windows.

Installation details

• Download-and-install step (ideas from the ghcup installer) and from Tauri:

  • Linux/Unix/MacOSX/MSYS2/Cygwin/WSL2: Run in a terminal (as a non-root user):

    curl --proto '=https' --tlsv1.2 -sSf https://kuu.se/your-installer.sh | sh
    

  • MS Windows: Run in a PowerShell session (as a non-admin user):

    Set-ExecutionPolicy Bypass -Scope Process -Force;[System.Net.ServicePointManager]::SecurityProtocol = [System.Net.ServicePointManager]::SecurityProtocol -bor 3072; try { & ([ScriptBlock]::Create((Invoke-WebRequest https://kuu.se/your-installer.ps1 -UseBasicParsing))) -Interactive -DisableCurl } catch { Write-Error $_ } 
    

• Install details:

  • Linux/Unix/MacOSX/MSYS2/Cygwin/WSL2:
    
    • Download and run your-installer.sh (done by the command above).
      The your-installer.sh script should:
      • Automatically download bootstrap.tcl.
        
      • Try to find tclsh or jimsh0 in PATH.
        
      • If found, run tclsh bootstrap.tcl.
        
      • If not found, try to find cc in PATH.
        
      • If a compiler is present found, automatically download and compile jimsh0.c.
        
      • If no compiler is present, detect OS, and download a precompiled jimsh0 interpreter for the current OS.
        
      • There is no precompiled jimsh0 for MacOSX, so in such a case, an error message should be shown with something like "Install Xcode".
      • Run ./jimsh0 bootstrap.tcl to start the installation.
        
  • MS Windows (PowerShell):
    
    • Download and run your-installer.ps1 (done by the command above).
      The your-installer.ps1 script should:
      • Automatically download bootstrap.tcl.
        
      • Try to find tclsh or jimsh0 in PATH.
        
      • If no Tcl interpreter was found, automatically download a precompiled jimsh0 interpreter for MS Windows.
      • Run jimsh0 bootstrap.tcl to start the installation.
        

The bootstrap.tcl script

The bootstrap.tcl script should setup the environment as described in the fnest README.

Related (bootstrap script) - DOSH

• Single script for both DOS CMD and UNIX SHELL

More bootstrap script examples

• myscript.cmd from https://nastytester.com/posts/script-that-works-in-windows-and-linux.html
• myscriptwithargs.cmd from https://superuser.com/questions/188143/how-to-detect-windows-os-in-shell-script

See also

• jimsh
• Bootstrap jimsh