A rust example to read perl's build configuration

main.rs

use std::process::Command;
use std::collections::HashMap;
use std::result::Result;
use regex::Regex;

fn perl_config(configs: Vec<&str>) -> Result<String, String> {
    let mut cmd = Command::new("perl");
    cmd.arg("-wle");
    cmd.arg(r#"
use strict;
use Config;
print join "\t", $_, ($Config{$_} // '') for @ARGV;
"#
        );
    
    for cf in configs.iter() {
        cmd.arg(cf);
    }
        
    let out = cmd.output().expect("perl Config outputs");

    if out.stderr.len() > 0 {
        return Err(String::from_utf8(out.stderr).unwrap());
    }
    
    Ok(String::from_utf8(out.stdout).unwrap())
}

fn perl_config_dict(configs: Vec<&str>) -> Result<HashMap<String, String>, String> {
    let config = perl_config(configs)?;
    let lines = config.lines().map(String::from).collect();
    Ok(lines_to_hashmap(lines))
}

fn lines_to_hashmap(lines: Vec<String>) -> HashMap<String,String> {
    let mut dict = HashMap::new();
    for line in lines.iter() {
        let kv: Vec<String> = line.splitn(2, '\t').map(String::from).collect();
        if kv.len() == 2 {
            dict.insert(kv[0].clone(), kv[1].clone());
        }
    }
    dict
}

fn main() {
    let config = perl_config_dict(vec![
        "ccflags",
        "useithreads",
        "usemultiplicity",
        "PERL_VERSION",
        "PERL_API_VERSION",
    ]).unwrap();
    println!("config = {:?}", config);
    
    let re_includes_and_defines = Regex::new(r"^-[ID]").unwrap();
    let ccflags: Vec<String> = config.get("ccflags").unwrap().split_whitespace()
        .map(String::from)
        .filter(|s| re_includes_and_defines.is_match(s)).collect();

    println!("ccflags = {:?}", ccflags);
}