R_LANG(3)

💖 R_LANG — the radare2 scripting-language glow-up 💖

okay bestie, sit down, hydrate, because today we're talking about r_lang, aka the scripting language support library for radare2. it lives in the Library Functions Manual section, and it's genuinely iconic. no cap. 🎀

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✨ SYNOPSIS ✨

this bit is just showing you the public header and the absolute minimum include you need to build against the r_lang API — like, the tiniest little compile-time peek at the library. nothing more, nothing less. 🦋

#include <r_lang.h>

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🌸 DESCRIPTION 🌸

here's the lowdown on what r_lang actually is and how it's built: it's a plugin-driven runtime that lets radare2 host and run scripts and REPLs from a whole bunch of different languages. it's giving "polyglot queen." 👑

the r_lang library gives radare2 scripting language support through a plugin-based system. it lets you execute code in various programming languages right inside the radare2 environment — so automation, custom commands, and extensions are all on the table. 🔥

at the very heart of the API is struct r_lang_t, and she manages loaded language plugins, user pointers, and execution sessions. language implementations register a struct r_lang_plugin_t, supplying callbacks for:

• initialization
• running code
• running files
• interactive prompts
• cleanup

so yeah, every language plugin brings its own little callbacks and r_lang handles the hosting. teamwork makes the dream work fr fr 🫶

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🌈 INITIALIZATION 🌈

this section is all about creating and destroying an r_lang handle, and how to associate runtime state with it (usually that's a pointer to an RCore instance, iykyk).

create a new language instance:

RLang *lang = r_lang_new();

set user pointer (usually RCore):

r_lang_set_user_ptr(lang, core);

free when done:

r_lang_free(lang);

💀 do not forget that free. she's not going to clean up after herself, bestie.

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⭐ EXECUTION ⭐

these are the calls you use to select a language plugin, execute code buffers, or invoke script files. the typical host (that's radare2, hi) selects a plugin and then calls one of the run helpers below. it's a whole little routine. 💅

select a language:

r_lang_use(lang, "qjs"); // QuickJS JavaScript

execute code string:

const char *code = "console.log('Hello from r2!');";
r_lang_run_string(lang, code);

execute code with length:

r_lang_run(lang, code, strlen(code));

execute script file:

r_lang_run_file(lang, "script.js");

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🎀 INTERACTIVE MODE 🎀

interactive features (REPLs!! the main character energy is unreal) are implemented per-plugin, and you enter them through the generic prompt helper. this is the spot to learn how to start a language REPL from the embedding application. 🧚

start interactive prompt:

r_lang_prompt(lang); // Interactive REPL

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🍓 ARGUMENTS 🍓

scripts that expect positional arguments get them through the argv helpers. the API lets hosts set argc/argv before invoking a file or an entry callback. order matters, okay? 😭

set command-line arguments for scripts:

char *argv[] = {"script.js", "arg1", "arg2"};
r_lang_set_argv(lang, 3, argv);

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💜 DEFINITIONS 💜

use the definitions API to expose host pointers and typed variables to language runtimes. the host can add and remove named definitions that scripts can see. it's literally show-and-tell but for your host state. 🙈

define variables accessible from scripts:

int value = 42;
r_lang_define(lang, "int", "my_var", &value);

remove definition:

r_lang_undef(lang, "my_var");

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👑 LANGUAGES 👑

this section highlights notable, supported language entry points rather than exhaustively listing every plugin. it focuses on the two integration styles commonly used by radare2: an embedded VM and native C plugin/script support. two very different vibes, both slaying.

• JavaScript: a native QuickJS (qjs) plugin is available and is the canonical embedded scripting VM inside radare2. Use r_lang_use(..., "qjs") to select it and r_lang_run_string / r_lang_run_file to execute code. ⭐
• C scripts: the C plugin compiles a .c file into a shared library, opens the resulting library, resolves an entry symbol and calls it with the current RCore * (stored in r_lang->user) and the configured argc, argv. The C entry must have the signature void entry(RCore *core, int argc, const char **argv). 🔥

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💅 EXAMPLES 💅

the examples below show common usage patterns observed in the radare2 core: invoking QuickJS code, running inline expressions via the #! hashbang helper, and how C scripts are compiled and invoked with the host RCore pointer. real-world rep, periodt.

execute JavaScript code:

#include <r_lang.h>

int main() {
    RLang *lang = r_lang_new();
    r_lang_use(lang, "qjs");

    const char *js_code = R"js(
        console.log("Hello from JavaScript!");
        var addr = 0x1000;
        console.log("Address: 0x" + addr.toString(16));
    )js";

    r_lang_run_string(lang, js_code);
    r_lang_free(lang);
    return 0;
}

define and use variables:

RLang *lang = r_lang_new();
int my_int = 12345;
r_lang_define(lang, "int", "global_var", &my_int);

r_lang_use(lang, "qjs");
r_lang_run_string(lang, "console.log('Value: ' + global_var);");

r_lang_free(lang);

execute script file:

r_lang_run_file(lang, "script.js");

hashbang and -e usage (used by the #! command in libr/core/cmd_hash.inc.c):

// the command handler implemented in libr/core/cmd_hash.inc.c parses `#!` lines
// and: selects the requested plugin (r_lang_get_by_name/r_lang_use_plugin),
// sets argv via r_lang_set_argv when file arguments are present, and either
// runs a file with r_lang_run_file or runs an expression with r_lang_run_string
// when `-e` is passed; expressions prefixed with `base64:` are decoded first.

C script example (how the C plugin runs code):

/* example.c */
#include <r_core.h>

void entry(RCore *core, int argc, const char **argv) {
    char *s = r_core_cmd_str (core, "?E hello world");
    printf("%s", s);
    free (s);
}

/* The C plugin will compile this file to a shared library and call `entry` with
   the host RCore pointer (r_lang->user) and any argv configured via
   r_lang_set_argv(). */

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🦋 SEE ALSO 🦋

• r_core(3)
• r_util(3)

go read those too, bestie, they're the supporting cast and they ate. 💖

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and that's the whole page!! this one came from the Debian fam, dated September 21, 2025, and it's the R_LANG(3) manual — so go forth and script, queen. 🎀✨👑💅