How to execute shell commands in Node.js?

Published October 26, 2020

To execute shell commands from Node.js, you can use the exec() function from the child_process module in Node.js. The execution of the exec() function is asynchronous.

// import exec method from child_process module
const { exec } = require("child_process");

// execute mkdir command asynchronously
// to make a directory with name hello
exec("mkdir hello");

The exec() takes 1 required argument, and 2 optional arguments:

  • The command to run on the shell as the first argument. It should be of type string (Required).
  • Options while executing the command. It should be of type object (Optional).
    • cwd: to set the current working directory
    • env: to set the environment variable
    • timeout: to set the maximum time for the command to run. etc. are some of the options available. To see more options see Node.js exec() method options.
  • A callback function to execute when the process terminates (Optional).
    • It is supplied with an Error object as the first parameter if there is an error.
    • It is supplied with an output from the stdout as the second parameter.
    • it supplied with a stderr as the third parameter.

Let's say we have to make three files called hello1.txt, hello2.txt, and hello3.txt from a Node.js process.

let's make use of the exec() function and pass the string touch hello1.txt hello2.txt hello3.txt to make three txt files like this,

// import exec method from child_process module
const { exec } = require("child_process");

// execute touch command
// to create three text file
exec("touch hello1.txt hello2.txt hello3.txt");

Now let's set some fake environment variables by passing objects with the env property as the second argument.

// import exec method from child_process module
const { exec } = require("child_process");

// execute touch command
// to create three text file
exec("touch hello1.txt hello2.txt hello3.txt", {
  env: {
    NODE_ENV: "production",
  },
});

Also, let's make sure that that the output is logged to the console by passing a callback function as the third parameter to the function.

// import exec method from child_process module
const { exec } = require("child_process");

// execute touch command
// to create three text file
exec(
  "touch hello1.txt hello2.txt hello3.txt",
  {
    // setting fake environment variable 😁
    env: {
      NODE_ENV: "production",
    },
  },
  (error, stdout, stderror) => {
    // if any error while executing
    if (error) {
      console.error("Error: ", error);
      return;
    }

    console.log(stdout); // output from stdout
    console.error(stderror); // std errors
  }
);

Now those three txt files will be created. 😃

See this example live in repl.it.

Feel free to share if you found this useful 😃.


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