Executing C code with JS -- using Node’s exec() function
Tags: javascript, c, programming, learning
Published: 2024-05-12 11:20:29

As I've been delving into the fundamentals of Linux, hardware, and networking, I've grown increasingly fascinated by how programs in various languages are ultimately translated into machine language for execution. This realization sparked my interest in seeing whether I could execute code across different programming paradigms. This led me to successfully run a C program using JavaScript. In this post, I'll explain the process step-by-step, shedding light on both the method and the rationale behind this approach.


## **1. Preparing the C Program**

Let's start with the basics. We need a C program that we intend to run through our JavaScript code. For this demonstration, I chose a simple C program that accepts command-line arguments and prints them. Here's the `main.c` code:

```c
#include <stdio.h>
#include <stdlib.h>

int main (int argc, char *argv[]) {
    for (int i=1; i < argc; i++) {
        printf("%s\n", argv[i]);
    }
    exit(0);
}
```

This program iterates through given command-line arguments and prints each one on a new line.

## **2. Compiling the C Program**

Before we can run our C code through JavaScript, we need to compile it into an executable. This step transforms the high-level C code into machine code that the computer's processor can execute directly. We use `gcc`, a popular C compiler:

```bash
gcc -o main main.c
```

Testing it directly in the terminal:

```bash
./main hello!
```

Output:
```
hello!
```

## **3. Crafting the JavaScript Executor**

Now for the fun part—creating a JavaScript program that can execute our C program. We'll use Node.js and its `child_process` module, which allows us to run shell commands directly from JavaScript. This module is part of the Node.js core, so no additional installations are necessary.

Here's `main.js`:

```javascript
const { exec } = require('child_process');

const argValue = 'hello!';  // Sample arguments
const command = `./main ${argValue}`;

exec(command, (error, stdout) => {
    if (error) {
        console.error(`Error: ${error.message}`);
        return;
    }
    console.log(`${stdout}`);
});
```

## **4. Putting It All Together**

Finally, let's execute the JavaScript program to see if it successfully calls our C executable:

```bash
node main.js
```

Output:
```
hello!
```

It works flawlessly! This setup highlights a key concept: compiled languages like C, C++, Go, and Rust convert code into machine language directly, which means their executables can be invoked from scripts written in other languages. However, for interpreted languages like Java and Python, each execution involves the interpreter, which complicates direct calls from scripts in other languages.

## **Why This Matters**

Understanding how different programming languages interact at the system level not only expands our technical repertoire but also enhances our ability to solve complex problems in innovative ways. By harnessing the strengths of both compiled and interpreted languages, we can design systems that are both powerful and flexible.

This exploration is just the tip of the iceberg. The possibilities are vast and varied—ranging from automating system-level tasks to creating complex multi-language architectures. So, let your curiosity lead the way and keep experimenting!

---

If you're intrigued by the idea of polyglot programming—using multiple programming languages within the same project to leverage each language's strengths—you might find this article on MetaCall helpful: [Polyglot Programming with MetaCall](https://dev.to/siddhantkcode/polyglot-programming-with-metacall-308m). It’s a great resource for those looking to dive deeper into creating versatile, multi-language software solutions. Dive in, and happy coding!

---

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