http://qs1969.pair.com?node_id=479645

esskar has asked for the wisdom of the Perl Monks concerning the following question:

Hi, it's me again! :)
You may know that I embedded perl.
I keep several persistent interpreters in different threads.
Do you know a way to set %ENV and the workingdirectory and redirect STDIN without writing external Perlcode but calling the PerlAPI from my C/C++ program?
Thanks for help!
  • Comment on Perl Embedded: Setting %ENV, STDIN and Workingdirectory

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Re: Perl Embedded: Setting %ENV, STDIN and Workingdirectory
by tlm (Prior) on Jul 30, 2005 at 23:09 UTC

    I'm sure there are more enlightened ways to do this, but my ignorant (and 100% untested) approach would be to use eval_pv to evaluate a string of Perl code within my C program.

    As far as changing the working directory, at least in Unix, I'd just use chdir(2); no need to get perl involved for this.

    the lowliest monk

[reply]
      well, since i have multiple threads, i think using the windows equivalent to chdir would affect all threads. But thats not a good idea, because one script has to run in a different directory than a other.
      But thanks for the eval_pv hint; i will be testing it!
[reply]
Re: Perl Embedded: Setting %ENV, STDIN and Workingdirectory
by esskar (Deacon) on Jul 31, 2005 at 23:28 UTC
    Okay; setting %ENV is rather simple.
    To make it simple, i wrapped part of perls variable types and their functionality in a C++ Class.
    Read more... (2 kB)
    then i wrote a function as part of my interpreter class that returns a hash object 
    Hash Interpreter::GetHash(const char *name, bool create /*=false*/) {
    Hash hash;

    hash.Attach(get_hv(name, create));

    return hash;
}

    [download]
    And now i'm able to do the follwing fun stuff: 
    Perl::Hash perlenv = m_perl->GetHash("ENV");
if(perlenv.ValidPtr()) {
    perlenv.Store("foo", Perl::Scalar("bar"));
    perlenv.Store("bar", Perl::Scalar("foo"));
}

    [download]
    Fun, isn't it? :)
[reply]
[d/l]
[select]
Re: Perl Embedded: Setting %ENV, STDIN and Workingdirectory
by esskar (Deacon) on Aug 02, 2005 at 20:56 UTC
    well; i haven't seen it.
    it's actually that simple 
    Scalar Interpreter::Eval(const char *code, bool croak) {
   Scalar retval;
   retval.Attach(eval_pv(code, croak));
   return retval;
}

void PerlObj::RedirectStdout(const std::string & filename) {
    std::string code = "";
    
    code += "open(YAPPPSSTDOUTSAVE, \">&STDOUT\");";
    code += "open(YAPPPSSTDOUTFILE, \">";
    code += MakeUnixFilename(filename);
    code += "\") or die \"Unable to override STDOUT!\";";
    code += "open(STDOUT, \">&YAPPPSSTDOUTFILE\") or \
            die \"Unable to override STDOUT!\";";
        
    m_perl->Eval(code.c_str(), true);
    m_redirectstdout = true;
}

void PerlObj::RedirectStdin(const std::string & filename) {
    std::string code = "";
    
    code += "open(YAPPPSSTDINSAVE, \"<&STDIN\");";
    code += "open(YAPPPSSTDINFILE, \"<";
    code += MakeUnixFilename(filename);
    code += "\") or die \"Unable to override STDIN!\";";
    code += "open(STDIN, \"<&YAPPPSSTDOUTFILE\") or \
            die \"Unable to override STDIN!\";";
    
    m_perl->Eval(code.c_str(), true);
    m_redirectstdin = true;
}

void PerlObj::ResetStdio() {
    std::string code = "";
    if(m_redirectstdin) {        
        code += "open(STDIN, \"<&YAPPPSSTDINSAVE\");";
        code += "close(YAPPPSSTDINFILE);";
        m_redirectstdin = false;
    }
    if(m_redirectstdout) {        
        code += "open(STDOUT, \">&YAPPPSSTDOUTSAVE\");";
        code += "close(YAPPPSSTDOUTFILE);\n";
        m_redirectstdout = false;
    }
    if(code != "")
        m_perl->Eval(code.c_str(), true);
}

    [download]
    and no i can just call "chdir" to set the workingdirectory because it will just set the wd of the current interpreter.
    It's fun! :) i'm happy!
[reply]
[d/l]

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