the inner SHELL cross os compatibility between freebsd and windows msys2 about b2

[Kojoley]

You are using OS shell and observing OS command parsing differences, that's obviously not SHELL fault.
I guess you are looking for a cross-platform way to create a file with some content, but unfortunately I don't think B2 provides such an function currently.

[grisumbras]

import print ;
make a.txt : : @write ;
rule write ( target : srcs * : props : ) {
  print.output $(target) ;
  print.text "line1" "line2" : overwrite ;
}

[fasxmut]

import print ;
make a.txt : : @write ;
rule write ( target : srcs * : props : ) {
  print.output $(target) ;
  print.text "line1" "line2" : overwrite ;
}

Thanks I tried. But I can't execute your script as it said args error. And it seems that make rule can not pass variables to actions except file names.
And it is weird that the print.text only works if the target is console, not works on output file.

[grisumbras]

My snippet had a typo (a didn't test it when I posted it). The correct jam script that creates a project-config.jam in current directory is

make project-config.jam : : @write : <location>. ;

rule write ( target : srcs * : props * : ) {
  if "$(var2)" {
    echo "var2 is $(var2)" ;
  } else {
    print.output $(target) ;
    print.text
        "constant var2 : $(var) ;"
        ""
      : overwrite
      ;
  }
}

I did't understand your remarks about passing variables to rules and print.text not working on files, though.

[fasxmut]

My snippet had a typo (a didn't test it when I posted it). The correct jam script that creates a project-config.jam in current directory is

make project-config.jam : : @write : <location>. ;

rule write ( target : srcs * : props * : ) {
  if "$(var2)" {
    echo "var2 is $(var2)" ;
  } else {
    print.output $(target) ;
    print.text
        "constant var2 : $(var) ;"
        ""
      : overwrite
      ;
  }
}

I did't understand your remarks about passing variables to rules and print.text not working on files, though.

I try it again this time, your jamfile script has no errors, and the print.text works on files too.
The passing variables to rules I mean, the rule or actions take variables from the arguments (just like function parameters), not take variables from global scope.

[grafikrobot]

The passing variables to rules I mean, the rule or actions take variables from the arguments (just like function parameters), not take variables from global scope.

@fasxmut target actions, which is what the print utility module is using for the file output, only take inputs through variables. They can be either global or bound (https://www.bfgroup.xyz/b2/manual/main/index.html#jam.language.rules.action_modifiers). What @grisumbras demonstrated accepting rule arguments like your original example. Can you explain in more details what you are trying to accomplish.