Execute and get the output of a shell command in node js

Question

In a node js  I d like to find a way to obtain the output of a Unix terminal command  Is there any way to do this   function getCommandOutput commandString          now how can I implement this function         getCommandOutput  ls   should print the terminal output of the shell command  ls

User · Answer

You can use the util library that comes with nodejs to get a promise from the exec command and can use that output as you need. Use restructuring to store the stdout and stderr in variables.

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const util = require('util');
const exec = util.promisify(require('child_process').exec);

async function lsExample() {
  const {
    stdout,
    stderr
  } = await exec('ls');
  console.log('stdout:', stdout);
  console.error('stderr:', stderr);
}
lsExample();

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User · Answer

You re looking for child process  var exec   require  child process   exec  var child   child   exec command     function  error  stdout  stderr          console log  stdout      stdout         console log  stderr      stderr         if  error     null              console log  exec error      error                      As pointed out by Renato  there are some synchronous exec packages out there now too  see sync-exec that might be more what yo re looking for  Keep in mind though  node js is designed to be a single threaded high performance network server  so if that s what you re looking to use it for  stay away from sync-exec kinda stuff unless you re only using it during startup or something

User · Answer

Requirements  This will require Node js 7 or later with a support for Promises and Async Await   Solution  Create a wrapper function that leverage promises to control the behavior of the child process exec command   Explanation  Using promises and an asynchronous function  you can mimic the behavior of a shell returning the output  without falling into a callback hell and with a pretty neat API  Using the await keyword  you can create a script that reads easily  while still be able to get the work of child process exec done   Code sample  const childProcess   require  child process             param  string  command A shell command to execute     return  Promise lt string gt   A promise that resolve to the output of the shell command  or an error     example const output   await execute  ls -alh        function execute command                param  Function  resolve A function that resolves the promise       param  Function  reject A function that fails the promise       see https   developer mozilla org en-US docs Web JavaScript Reference Global Objects Promise         return new Promise function resolve  reject                    param  Error  error An error triggered during the execution of the childProcess exec command         param  string Buffer  standardOutput The result of the shell command execution         param  string Buffer  standardError The error resulting of the shell command execution         see https   nodejs org api child process html child process child process exec command options callback             childProcess exec command  function error  standardOutput  standardError          if  error            reject             return                 if  standardError            reject standardError            return                 resolve standardOutput                     Usage  async function main       try       const passwdContent   await execute  cat  etc passwd         console log passwdContent       catch  error        console error error toString            try       const shadowContent   await execute  cat  etc shadow         console log shadowContent       catch  error        console error error toString            main      Sample Output  root x 0 0   root  bin bash  output trimmed  bottom line it succeeded   Error  Command failed  cat  etc shadow cat   etc shadow  Permission denied   Try it online   Repl it   External resources  Promises   child process exec   Node js support table

User · Answer

If you re using node later than 7 6 and you don t like the callback style  you can also use node-util s promisify function with async   await to get shell commands which read cleanly   Here s an example of the accepted answer  using this technique   const   promisify     require  util    const exec   promisify require  child process   exec   module exports getGitUser   async function getGitUser        const name   await exec  git config --global user name     const email   await exec  git config --global user email     return   name  email        This also has the added benefit of returning a rejected promise on failed commands  which can be handled with try   catch inside the async code

User · Answer

This is the method I m using in a project I am currently working on  var exec   require  child process   exec  function execute command  callback       exec command  function error  stdout  stderr   callback stdout           Example of retrieving a git user  module exports getGitUser   function callback       execute  quot git config --global user name quot   function name           execute  quot git config --global user email quot   function email               callback   name  name replace  quot  n quot    quot  quot    email  email replace  quot  n quot    quot  quot

User · Answer

Thanks to Renato answer  I have created a really basic example   const exec   require  child process   exec  exec  git config --global user name    err  stdout  stderr    gt  console log stdout     It will just print your global git username

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