Start a Tauri app which calls C function using sudo without password

Question

I have made a Tauri app. This app uses C in the backend. The C file contains multiple functions. Some functions use the sudo command to get data. I have started this C file in the Tauri app by writing the following function in src-tauri/srclib.rs:

#[command]
fn run_c_program() -> String {
    // Use absolute path from the project root
    let mut c_program_path = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
    c_program_path.pop(); // Go up from src-tauri directory
    c_program_path.pop(); // Go up from frontend directory
    c_program_path.push("backend");
    c_program_path.push("backend-c-file");
    
    println!("Looking for C program at: {:?}", c_program_path);
    
    // Execute the C program and capture output
    match Command::new(&c_program_path).output() {
        Ok(output) => {
            if output.status.success() {
                let stdout = String::from_utf8_lossy(&output.stdout).to_string();
                println!("C program output: {}", stdout);
                stdout
            } else {
                let stderr = String::from_utf8_lossy(&output.stderr).to_string();
                println!("C program error: {}", stderr);
                format!("Error: {}", stderr)
            }
        }
        Err(e) => {
            let error_msg = format!("Failed to execute C program at {:?}: {}", c_program_path, e);
            println!("{}", error_msg);
            error_msg
        }
    }
}

I have console logged this data using the following function in src/App.jsx:

    async function runCProgram() {
        const output = await invoke("run_c_program");
        setCProgramOutput(output);
        console.log(cProgramOutput);
    }

This correctly outputs the data.

However, because some of the functions require the sudo command, I can't view the output of any functions until I enter the sudo password. Instead, by default, I want to view the output of all non-sudo commands. If I enter the sudo password, I then want to view the output of all sudo commands

You execute a program, right? Does it matter that it was originally written in C? — Ted Lyngmo
– Ted Lyngmo, Commented Oct 2 at 15:10
It's not to see the results that you need to enter a password. It's for the program to successfully run sudo for you at all. Nothing computed by the commands run via sudo, and likely nothing computed by any other commands later in the program, is even available to be viewed until some time after you enter a password. — John Bollinger
– John Bollinger, Commented Oct 2 at 17:42
Occasionally it is appropriate for a script to use sudo to run some command. Very rarely it is appropriate for a compiled program. Usually it is better to require the user to acquire all needed privileges before running a script or program, however, such as by using sudo to run it, instead of expecting the script to run sudo. — John Bollinger
– John Bollinger, Commented Oct 2 at 17:47

user27793975 · Accepted Answer · 2025-10-04 12:07:04Z

Add an argument to the main function:

int main(int argc, char *argv[]) {

Inside the main function, add an if statement checking which argument was provided:

// If no arguments are provided, show usage
if (argc == 1) {
    printf("option_1\n");
    printf("option_2\n");
    printf("option_3\n");
    printf("option_4\n");
}

// Handle specific function calls via command-line arguments
for (int i = 1; i < argc; i++) {
    if (strcmp(argv[i], "option_1") == 0) {
        option_1_function();
    }
    else if (strcmp(argv[i], "option_2") == 0) {
        option_2_function();
    }
    else if (strcmp(argv[i], "option_3") == 0) {
        option_3_function();
    }
    else if (strcmp(argv[i], "option_4") == 0) {
        option_4_function();
    }
}

Inside src/App.jsx, run the C function which needs running:

const [cProgramOutput, setCProgramOutput] = useState("");
async function runCProgram() {
    const output = await invoke("run_c_program", { "function": "option_2" });
    setCProgramOutput(output);
    console.log(cProgramOutput);
}

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