Node.js: child_process.exec(command[, options][, callback]) : Execute system commands

child_process module allows user to execute external processes. For example, you can comunicate external applications (like notepad++) installed in your system.

HelloWorld.js

var exec = require('child_process').exec;

var applicationName = 'notepad';
exec(applicationName);

When you execute above application in windows environment, it opens notepad application.

Signature of exec function looks like below.

child_process.exec(command[, options][, callback])

Below table summarizes the arguments of exec function.

Argument	Type	Description
command	String	Command to execute
Options	Object	Below table summarizes different options provided by exec command. Option Type Description cwd string Current working directory of child process. Default value is null. env Object Environment key, value pairs. Default value is null. encoding string Default valueis utf-8. If encoding is 'buffer', or an unrecognized character encoding, Buffer objects will be passed to the callback instead. shell string Shell to execute the command with. Default: '/bin/sh' on UNIX, process.env.ComSpec on Windows. timeout number Default value is 0. If timeout is greater than 0, the parent will send the signal identified by the killSignal property (the default is 'SIGTERM') if the child runs longer than timeout milliseconds. maxBuffer number Largest amount of data in bytes allowed on stdout or stderr. If exceeded, the child process is terminated. Kill string or integer Default: 'SIGTERM' Uid number Sets the user identity of the process Gid number Sets the group identity of the process windowsHide boolean Hide the subprocess console window that would normally be created on Windows systems. Default: false.
callback	Function	Function to be called, when the process terminates. This function takes three arguments. Below table summarizes the arguments of callback function. Argument Type error Error stdout String (or) Buffer stderr String (or) Buffer On success, error will be null. On error, error will be an instance of Error. stdout and stderr objects represents the stdout and stderr output of the child process.

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