NodeJS Child Process Module<\/strong><\/h2>\n\n\n\nFor creating child processes, it is required to import the child process module using the below statement. <\/p>\n\n\n\n
Syntax:<\/strong><\/p>\n\n\n\nconst childProcess = require('child_process'); \n<\/pre><\/div>\n\n\nMethods to Create Child Process<\/strong><\/h2>\n\n\n\nLet’s now look at some of the methods that can be used to create child processes in NodeJs.<\/p>\n\n\n\n
1. spawn()<\/strong><\/h3>\n\n\n\nThis method takes commands, arguments, and options to start a new process. The options can contain shell as a boolean value, and “true” runs the command inside the shell. By default, the value is false which will not execute the command on the shell, so it is important to pass the shell as true.<\/p>\n\n\n\n
Syntax:<\/strong><\/p>\n\n\n\nspawn(command[,arguments][,options])\n<\/pre><\/div>\n\n\nExample:<\/strong><\/p>\n\n\n\nHere we are using the spawn method to create a child process that will execute the command pass as an argument. The result of this method is equivalent to the result that comes when passing the command mkdir new-folder in the shell.<\/p>\n\n\n
\nconst { spawn } = require('child_process');\nconst child = spawn('mkdir', ['new-folder'], {shell: true});\n\nchild.stdout.on('data', (data) => {\n console.log(`stdout: ${data}`);\n});\n \nchild.stderr.on('data', (data) => {\n console.error(`stderr: ${data}`);\n});\n\nchild.on('close', () => {\n console.log('child process closed');\n});\n<\/pre><\/div>\n\n\nOutput:<\/strong><\/p>\n\n\n\n![\"New](\"https:\/\/codeforgeek.com\/wp-content\/uploads\/2022\/10\/new-folder-created.png\")
New Folder Created<\/figcaption><\/figure>\n\n\n\n![\"Spawn](\"https:\/\/codeforgeek.com\/wp-content\/uploads\/2022\/10\/spawn-example-output.png\")
<\/figure>\n\n\n\n2. exec()<\/strong><\/h3>\n\n\n\nThis method takes a command, options, and a callback function in which we can write the code to log the error or success message.<\/p>\n\n\n\n
Syntax:<\/strong><\/p>\n\n\n\nexec(command[, options][, callback])\n<\/pre><\/div>\n\n\nExample:<\/strong><\/p>\n\n\n\nHere we are executing the same command as the previous example by using the exec() method. We are passing the command and argument together instead of passing them separately like in the case of the spawn method.<\/p>\n\n\n
\nconst { exec } = require('child_process'); \nexec('mkdir new-folder', (err) => { \n if (err) { \n console.error(err); \n return; \n } \n console.log("New folder Created"); \n}); \n<\/pre><\/div>\n\n\nOutput:<\/strong><\/p>\n\n\n\n![\"Exec](\"https:\/\/codeforgeek.com\/wp-content\/uploads\/2022\/10\/fork-example-output.png\")
We already created a folder with the name new-folder<\/strong> using the spawn method so it returns an error.<\/figcaption><\/figure>\n\n\n\n3. fork()<\/strong><\/h3>\n\n\n\nThis method is similar to spawn but it provides a way of communication between the parent and child process via the IPC communication channel by using the send method.<\/p>\n\n\n\n
Syntax:<\/strong><\/p>\n\n\n\nfork(modulePath[, args][, options])\n<\/pre><\/div>\n\n\nExample:<\/strong><\/p>\n\n\n\nHere we have established a channel between the parent file parent.js and the child file child.js by using the fork module. Then send a message from child.js to parent.js to see that they are able to communicate, once received the message at both ends, we close the child process because it is no longer needed.<\/p>\n\n\n\n
parent.js<\/strong><\/p>\n\n\n\nconst { fork } = require('child_process');\n \nconst child = fork(__dirname + '\/child.js');\n \nchild.on('message', function(message) {\n console.log("Message from child: " + message.msg);\n});\n \nchild.send({ msg: 'This is parent process' });\n \n<\/pre><\/div>\n\n\nchild.js<\/strong><\/p>\n\n\n\nprocess.on('message', function(message) {\n console.log("Message from parent: " + message.msg);\n });\n \nprocess.send({ msg: 'This is child process' });\n<\/pre><\/div>\n\n\nOutput:<\/strong><\/p>\n\n\n\n![\"Fork](\"https:\/\/codeforgeek.com\/wp-content\/uploads\/2022\/10\/fork-example-output-1.png\")
<\/figure>\n\n\n\nSummary<\/strong><\/h2>\n\n\n\nChild Process is helpful for running various processes simultaneously, this helps in utilizing multitasking functionality in Node.js since by default Node.js runs every process on a single thread. This is very useful when creating a large-scale Node.js Application<\/a> running many tasks at a time, without blocking the other part of the code. <\/p>\n\n\n\nChild processes run independently from each other so does not interrupt other processes. There are various methods to start a child process providing different implementations and features. Hope this article helps you to understand the concept of the child process in Node.js.<\/p>\n\n\n\n
Reference<\/strong><\/h2>\n\n\n\n
\nconst childProcess = require('child_process'); \n<\/pre><\/div>\n\n\nMethods to Create Child Process<\/strong><\/h2>\n\n\n\nLet’s now look at some of the methods that can be used to create child processes in NodeJs.<\/p>\n\n\n\n
1. spawn()<\/strong><\/h3>\n\n\n\nThis method takes commands, arguments, and options to start a new process. The options can contain shell as a boolean value, and “true” runs the command inside the shell. By default, the value is false which will not execute the command on the shell, so it is important to pass the shell as true.<\/p>\n\n\n\n
Syntax:<\/strong><\/p>\n\n\n\nspawn(command[,arguments][,options])\n<\/pre><\/div>\n\n\nExample:<\/strong><\/p>\n\n\n\nHere we are using the spawn method to create a child process that will execute the command pass as an argument. The result of this method is equivalent to the result that comes when passing the command mkdir new-folder in the shell.<\/p>\n\n\n
\nconst { spawn } = require('child_process');\nconst child = spawn('mkdir', ['new-folder'], {shell: true});\n\nchild.stdout.on('data', (data) => {\n console.log(`stdout: ${data}`);\n});\n \nchild.stderr.on('data', (data) => {\n console.error(`stderr: ${data}`);\n});\n\nchild.on('close', () => {\n console.log('child process closed');\n});\n<\/pre><\/div>\n\n\nOutput:<\/strong><\/p>\n\n\n\nNew Folder Created<\/figcaption><\/figure>\n\n\n\n<\/figure>\n\n\n\n2. exec()<\/strong><\/h3>\n\n\n\nThis method takes a command, options, and a callback function in which we can write the code to log the error or success message.<\/p>\n\n\n\n
Syntax:<\/strong><\/p>\n\n\n\nexec(command[, options][, callback])\n<\/pre><\/div>\n\n\nExample:<\/strong><\/p>\n\n\n\nHere we are executing the same command as the previous example by using the exec() method. We are passing the command and argument together instead of passing them separately like in the case of the spawn method.<\/p>\n\n\n
\nconst { exec } = require('child_process'); \nexec('mkdir new-folder', (err) => { \n if (err) { \n console.error(err); \n return; \n } \n console.log("New folder Created"); \n}); \n<\/pre><\/div>\n\n\nOutput:<\/strong><\/p>\n\n\n\nWe already created a folder with the name new-folder<\/strong> using the spawn method so it returns an error.<\/figcaption><\/figure>\n\n\n\n3. fork()<\/strong><\/h3>\n\n\n\nThis method is similar to spawn but it provides a way of communication between the parent and child process via the IPC communication channel by using the send method.<\/p>\n\n\n\n
Syntax:<\/strong><\/p>\n\n\n\nfork(modulePath[, args][, options])\n<\/pre><\/div>\n\n\nExample:<\/strong><\/p>\n\n\n\nHere we have established a channel between the parent file parent.js and the child file child.js by using the fork module. Then send a message from child.js to parent.js to see that they are able to communicate, once received the message at both ends, we close the child process because it is no longer needed.<\/p>\n\n\n\n
parent.js<\/strong><\/p>\n\n\n\nconst { fork } = require('child_process');\n \nconst child = fork(__dirname + '\/child.js');\n \nchild.on('message', function(message) {\n console.log("Message from child: " + message.msg);\n});\n \nchild.send({ msg: 'This is parent process' });\n \n<\/pre><\/div>\n\n\nchild.js<\/strong><\/p>\n\n\n\nprocess.on('message', function(message) {\n console.log("Message from parent: " + message.msg);\n });\n \nprocess.send({ msg: 'This is child process' });\n<\/pre><\/div>\n\n\nOutput:<\/strong><\/p>\n\n\n\n<\/figure>\n\n\n\nSummary<\/strong><\/h2>\n\n\n\nChild Process is helpful for running various processes simultaneously, this helps in utilizing multitasking functionality in Node.js since by default Node.js runs every process on a single thread. This is very useful when creating a large-scale Node.js Application<\/a> running many tasks at a time, without blocking the other part of the code. <\/p>\n\n\n\nChild processes run independently from each other so does not interrupt other processes. There are various methods to start a child process providing different implementations and features. Hope this article helps you to understand the concept of the child process in Node.js.<\/p>\n\n\n\n
Reference<\/strong><\/h2>\n\n\n\n