Standalone script to run Tcl applications from packages using the - tclmain -m pkgname - syntax.

• Background information

This Tcl application provides a facility to run Tcl applications, display help pages and show demo applications for Tcl packages, similar like the Python __main__.py file is doing this for a Python package. In Python, if your provide a file __main__.py within your package, you can exectute this file directly using the syntax: python -m pkgname. The Tcl script tclmain.tcl does a similar thing. As usually for standalone scripts scripts the file extension will be removed, I will below use its name as tclmain.

In addition to this Python like approach providing separate files in the package itself, since version 0.2.0 (2023-09-30) it is as well supported to call a main function in the form of package::main argv. Here an example of such an implementation:

package provide testx 0.0.1

namespace eval ::testx { }

proc ::testx::hello {name} {
    puts "Hello ${name}!"
}   

proc ::testx::main {{argv {}}} {
    if {[llength $argv] != 1} {
        puts "Usage: tclmain -m testx NAME"
    } else {
        testx::hello [lindex $argv 0]
    }   
}

Here an example session:

[tclmain]$ export TCLLIBPATH=.
[tclmain]$ tclsh bin/tclmain.tcl -i testx 
package:  testx
version:  0.0.1
location: ./examples
[tclmain]$ tclsh bin/tclmain.tcl -m testx 
Usage: tclmain -m testx NAME
[tclmain]$ tclsh bin/tclmain.tcl -m testx  Tclmain
Hello Tclmain!

So the only thing a package writer needs to make it runnable directly as an application using tclmain is to provide this main function within the namespace which must have the same name as the package itself and getting only the argv as the first and only argument with a default of an empty list.

• currently only Linux/Unix systems are supported
• in principle the approach should work on Windows as well, but I can't test it properly
• you only need a single file for using the tclmain approach
• download the file tclmain.tcl (you need to press raw to get the file)
• make it executable using the chmod command
• rename it to tclmain and move it to a folder belonging to your PATH variable, I place mine into ~/.local/bin
• check the installation by writing tclmain in your terminal where you should see the help page
• done

Here is an example on how to execute programs or get help pages by a user or developer if a package developer used this facilities by creating several files in his/her package folder. These files tclmain_xyz.tcl needs not to be sourced in the pkgIndex.tcl file.

• tclmain - gives the help message
• tclmain -h, --help - gives the help message
• tclmain -i, --info - gives information about a Tcl package
• tclmain -m, --module pkgname - lists the available commands for the package pkgname
• tclmain -p, --package pkgname - lists the available commands for the package pkgname
• tclmain -p pkgname main - executes the file ending with _main.tcl within the package directory
• tclmain -p pkgname help - executes the file ending with _help.tcl which should provide the help pages for the packages, or get's a hint of how to get see them
• tclmain -p pkgname demo - executes the file ending with _demo.tcl which could provide a short demo
• tclmain -m pkgname xxx - executes the file ending _xxx.tcl and so on, may be this is better implemented as tclmain pkgname run xxx so as an command line argument to the tclmain_run.tcl script, only three letter commands should be provided

There should be as well a possibility to provide these facilities if you are not having access to the package folders. It can't be assumed that a lot of Tcl packages will offer this functionality at any time soon. In this case you should be able to place these files witin your own configuration folder like ~/.config/tclmain/pkgname_main.tcl or ~/.config/tclmain/pkgname_demo.tcl on a Linux/Unix system. That way you can add these facilities to Tcl packages which does not use the tclmain approach.

Colons in the package name should be replaced in this case with underlines. So for the package canvas::zoom the filename becomes canvas_zoom_main.tcl for instance.

The Tclsh should provide such an approach using a module/package flag like Python, for instance tclsh -m pkgname or tclsh -p pkgname

Here a few examples to add this functionality to existing packages. As tclmain strips of the pkgname argument, the first argument is run in the argv list.

Here is a example file examples/Markdown_main.tcl. Thsi file should be placed in the config folder for tclmain so on a Unix/Linux system here ~/.config/tclmain/Markdown_main.tcl.

This file using the Markdown library of Tcllib and your helper file Markdown_main.tcl which must be placed in .config/tclmain. You could execute this file then like this:

$  tclmain -m Markdown 
Missing command for package Markdown.
Available commands are: main
$  tclmain -m Markdown main
Usage: tclmain -m Markdown main mdfile|- ?htmlfile|-?
       instead of filenames as well - can be used to indicate stdin and stdout

Example:
   echo '**Hello World!**' |  tclmain -m Markdown main - out.html
   
$  echo '**Hello world!**'  | tclmain -m Markdown main -
<p><strong>Hello world!</strong></p>

Here an other example to run the Tk demo. Create a file Tk_demo.tcl with the following content:.

#!/usr/bin/env tclsh

foreach folder $auto_path {
    set demo [file join $folder demos widget]
    if {[file exists $demo]} {
        source $demo
        break
    }
}

The file is as well available in the repository in the examples section. Place this file in your config folder ~/.config/tclmain. Thereafter you can have the following session.

$ tclmain -i Tk
package:  Tk
version:  8.6.12
location: /usr/lib64
$ tclmain -m Tk
Missing command for package Tk.
Available commands are: demo
$ tclmain -m Tk demo

You should then see the following window:

Obviously you could have the same effect if you would place the files in the config folder

I started adding for some packages inbuild Tclmain support. More packages will follow, here are the links:

• tclinstall - installer package, commands main and help
• kroki4tcl - commands main and api
• yeti - commands help for yeti and ylex (showing the help pages)

Here is an example session for kroki4tcl:

$ tclmain -i kroki4tcl
package:  kroki4tcl
version:  0.4.0
location: /home/groth/.local/lib/kroki4tcl
$ tclmain -m kroki4tcl 
Missing command for package kroki4tcl.
Available commands are: main,api
$ tclmain -m kroki4tcl api | less -r

This is the output:

If all Tcl packages would have a file with under-help or underline-api at the end we would always be able to query the documentation in the same manner ... just dreaming ...

• main as default mode, but how to distinguis between command and arguments?
• more examples for the config folder, like Tk demo (done)
• currently the files in config folder will be evaluated first, what happend if the package developers will then create its own file pkg_name.tcl for instance?

• Tclers Wiki - for suggestions and ideas
• Issues - do tell bugs and issues