linux - Node.js - exec command for tar files works correctly first time, but produces corrupted tar contents upon subsequent execution -

i building web app node.js, , @ point need produce tar archive of directory of pdfs. application running on vm running ubuntu 14.04 server. code shown below:

function tardirectory(path, token, callback) {   var exec = require('child_process').exec;   var cmd = 'cd ' + path + ' && tar -cvf genericname-' + token + '.tar' + ' ' + token;    exec(cmd, function(error, stdout, stderr) {     console.log(stdout);     console.log(stderr);     if (error) {       console.error(error);     }     if(callback) callback();   }); } 

and tardirectory function called following code:

router.post('/files/generate', function(req, res, next) {   idlist = req.body['ids[]'];   token = req.body['token'];    // if single file being generated   if (typeof req.body['ids[]'] === "string"){       filehelper.generatefile(idlist[0], req.app.locals.site.basedir + "temp/", token);   }   // if multiple files being generated   else {     idlist.foreach(function(id) {       filehelper.generatefile(id, req.app.locals.site.basedir + "temp/", token);     });   }   filehelper.tardirectory(req.app.locals.site.basedir + "temp/", token, res.end); }); 

the code expects post request dynamic data generated button click in web app, , create files based on data , tar directory. works fine , good... first time. when click button first time in while, tar produced, , when open it, client-side pdfs identical ones on server. when click again within hour or so, though, receive tar file, when open archive , unpack it, pdfs corrupted , half expected byte size. @ loss here... had suspicion might related improper handling of stream closing, i'm not sure.

this code generates pdfs directory, tarred after generation:

function generatefile(id, path, token) {   var dirpath = path + token;   var filepath = path + token + "/file" + id + ".pdf";    console.log("creating file for: " + id);    try{     fs.statsync(dirpath).isdirectory();   } catch (err) {     fs.mkdirsync(dirpath);   }   // start file pdf generation   file = new pdfdocument();   output = fs.createwritestream(filepath);   output.on('close', function(){     return;   });    file.pipe(output);    // handle intricacies of file generation   file.text("file" + id + ".pdf");    // end file   file.end(); } 

1. is okay pdf files, before compressing?
2. in generatefile function have writestream, async. but, calling function sync., , start .tar compression without waiting before pdf generation complete, may cause issue.
3. as recommendation: try wrap generatefile promise, or iterate async., , start compression after files generation completed.

example bluebird:

var promise = require('bluebird');  function generatefile(id, path, token) {   return new promise(function(resolve, reject) {   var dirpath = path + token;   var filepath = path + token + "/file" + id + ".pdf";    console.log("creating file for: " + id);    try{     fs.statsync(dirpath).isdirectory();   } catch (err) {     fs.mkdirsync(dirpath);   }   // start file pdf generation   file = new pdfdocument();   output = fs.createwritestream(filepath);   output.on('close', function(){     return resolve();   });    output.on('error', function(error) {     return reject(error);   });    file.pipe(output);    // handle intricacies of file generation   file.text("file" + id + ".pdf");    // end file   file.end();   }); } 

pdfs generation , compressing.

 var promise = require('bluebird');      ....      //idlist.foreach(function(id) {     //      filehelper.generatefile(id, req.app.locals.site.basedir + "temp/", //token);});      //replace      promise.map(idlist, function(id) {       return filehelper.generatefile(id, req.app.locals.site.basedir + "temp/", token);     })     .then(function() {     //all files ready, start compressing     })     .catch(function(error) {     //we have error     });