node.js execute system command synchronously
Use ShellJS module.
exec function without providing callback.
Example:
var version = exec('node -v').output;
There's an excellent module for flow control in node.js called asyncblock. If wrapping the code in a function is OK for your case, the following sample may be considered:
var asyncblock = require('asyncblock');
var exec = require('child_process').exec;
asyncblock(function (flow) {
exec('node -v', flow.add());
result = flow.wait();
console.log(result); // There'll be trailing \n in the output
// Some other jobs
console.log('More results like if it were sync...');
});
See execSync library.
It's fairly easy to do with node-ffi. I wouldn't recommend for server processes, but for general development utilities it gets things done. Install the library.
npm install node-ffi
Example script:
var FFI = require("node-ffi");
var libc = new FFI.Library(null, {
"system": ["int32", ["string"]]
});
var run = libc.system;
run("echo $USER");
[EDIT Jun 2012: How to get STDOUT]
var lib = ffi.Library(null, {
// FILE* popen(char* cmd, char* mode);
popen: ['pointer', ['string', 'string']],
// void pclose(FILE* fp);
pclose: ['void', [ 'pointer']],
// char* fgets(char* buff, int buff, in)
fgets: ['string', ['string', 'int','pointer']]
});
function execSync(cmd) {
var
buffer = new Buffer(1024),
result = "",
fp = lib.popen(cmd, 'r');
if (!fp) throw new Error('execSync error: '+cmd);
while(lib.fgets(buffer, 1024, fp)) {
result += buffer.readCString();
};
lib.pclose(fp);
return result;
}
console.log(execSync('echo $HOME'));
Node.js (since version 0.12 - so for a while) supports execSync
:
child_process.execSync(command[, options])
You can now directly do this:
const execSync = require('child_process').execSync;
code = execSync('node -v');
and it'll do what you expect. (Defaults to pipe the i/o results to the parent process). Note that you can also spawnSync
now.