Integrate with External Tools via Tasks

Lots of tools exist to automate tasks like linting, building, packaging, testing, or deploying software systems. Examples include theTypeScript Compiler, linters likeESLint andTSLint as well as build systems likeMake,Ant,Gulp,Jake,Rake, andMSBuild.

These tools are mostly run from the command line and automate jobs inside and outside the inner software development loop (edit, compile, test, and debug). Given their importance in the development life cycle, it is helpful to be able to run tools and analyze their results from within VS Code. Tasks in VS Code can be configured to run scripts and start processes so that many of these existing tools can be used from within VS Code without having to enter a command line or write new code. Workspace or folder specific tasks are configured from thetasks.json file in the.vscode folder for a workspace.

Extensions can also contribute tasks using aTask Provider, and these contributed tasks can add workspace-specific configurations defined in thetasks.json file.

Note: Task support is only available when working on a workspace folder. It is not available when editing single files.

TypeScript Hello World

Let's start with a simple "Hello World" TypeScript program that we want to compile to JavaScript.

Create an empty folder "mytask", generate atsconfig.json file and start VS Code from that folder.

mkdir mytaskcd mytasktsc --initcode .

Now create aHelloWorld.ts file with the following content

function sayHello(name:string):void {  console.log(`Hello${name}!`);}sayHello('Dave');

Pressing⇧⌘B (Windows, LinuxCtrl+Shift+B) or runningRun Build Task from the globalTerminal menu show the following picker:

The first entry executes the TypeScript compiler and translates the TypeScript file to a JavaScript file. When the compiler has finished, there should be aHelloWorld.js file. The second entry starts the TypeScript compiler in watch mode. Every save to theHelloWorld.ts file will regenerate theHelloWorld.js file.

You can also define the TypeScript build or watch task as the default build task so that it is executed directly when triggeringRun Build Task (⇧⌘B (Windows, LinuxCtrl+Shift+B)). To do so, selectConfigure Default Build Task from the globalTerminal menu. This shows you a picker with the available build tasks. Selecttsc: build ortsc: watch and VS Code will generate atasks.json file. The one shown below makes thetsc: build task the default build task:

{  // See https://go.microsoft.com/fwlink/?LinkId=733558  // for the documentation about the tasks.json format  "version":"2.0.0",  "tasks": [    {      "type":"typescript",      "tsconfig":"tsconfig.json",      "problemMatcher": ["$tsc"],      "group": {        "kind":"build",        "isDefault":true      }    }  ]}

Thetasks.json example above does not define a new task. It annotates thetsc: build tasks contributed by VS Code's TypeScript extension to be the default build task. You can now execute the TypeScript compiler by pressing⇧⌘B (Windows, LinuxCtrl+Shift+B).

Task auto-detection

VS Code currently auto-detects tasks for the following systems: Gulp, Grunt, Jake, and npm. We are working with the corresponding extension authors to add support for Maven and the C#dotnet command as well. If you develop a JavaScript application using Node.js as the runtime, you usually have apackage.json file describing your dependencies and the scripts to run. If you have cloned theeslint-starter example, then executingRun Tasks from the global menu shows the following list:

If you have not already done so, install the necessary npm modules by runningnpm install. Now open theserver.js file and add a semicolon to the end of a statement (note the ESLint starter assumes statements without a semicolon) and execute theRun Tasks again. This time select thenpm: lint task. When prompted for the problem matcher to use, selectESLint stylish

Executing the task produces one error, shown in theProblems view:

In addition, VS Code created atasks.json file with the following content:

{  // See https://go.microsoft.com/fwlink/?LinkId=733558  // for the documentation about the tasks.json format  "version":"2.0.0",  "tasks": [    {      "type":"npm",      "script":"lint",      "problemMatcher": ["$eslint-stylish"]    }  ]}

This instructs VS Code to scan the output of thenpm lint script for problems using the ESLint stylish format.

For Gulp, Grunt, and Jake, the task auto-detection works the same. Below is an example of the tasks detected for thevscode-node-debug extension.

Tip: You can run your task throughQuick Open (⌘P (Windows, LinuxCtrl+P)) by typing 'task',Space and the command name. In this case, 'task lint'.

Task auto detection can be disabled using the following settings:

{  "typescript.tsc.autoDetect":"off",  "grunt.autoDetect":"off",  "jake.autoDetect":"off",  "gulp.autoDetect":"off",  "npm.autoDetect":"off"}

Custom tasks

Not all tasks or scripts can be auto-detected in your workspace. Sometimes it is necessary to define your own custom tasks. Assume you have a script to run your tests in order to set up some environment correctly. The script is stored in a script folder inside your workspace and namedtest.sh for Linux and macOS andtest.cmd for Windows. RunConfigure Tasks from the globalTerminal menu and select theCreate tasks.json file from template entry. This opens the following picker:

Note: If you don't see the list of task runner templates, you may already have atasks.json file in your folder and its contents will be open in the editor. Close the file and either delete or rename it for this example.

We are working on more auto-detection support, so this list will get smaller and smaller in the future. Since we want to write our own custom task, selectOthers from the list. This opens thetasks.json file with a task skeleton. Replace the contents with the following:

{  // See https://go.microsoft.com/fwlink/?LinkId=733558  // for the documentation about the tasks.json format  "version":"2.0.0",  "tasks": [    {      "label":"Run tests",      "type":"shell",      "command":"./scripts/test.sh",      "windows": {        "command":".\\scripts\\test.cmd"      },      "group":"test",      "presentation": {        "reveal":"always",        "panel":"new"      }    }  ]}

The task's properties have the following semantic:

• label: The task's label used in the user interface.
• type: The task's type. For a custom task, this can either beshell orprocess. Ifshell is specified, the command is interpreted as a shell command (for example: bash, cmd, or PowerShell). Ifprocess is specified, the command is interpreted as a process to execute.
• command: The actual command to execute.
• windows: Any Windows specific properties. Will be used instead of the default properties when the command is executed on the Windows operating system.
• group: Defines to which group the task belongs. In the example, it belongs to thetest group. Tasks that belong to the test group can be executed by runningRun Test Task from theCommand Palette.
• presentation: Defines how the task output is handled in the user interface. In this example, the Integrated Terminal showing the output isalways revealed and anew terminal is created on every task run.
• options: Override the defaults forcwd (current working directory),env (environment variables), orshell (default shell). Options can be set per task but also globally or per platform. Environment variables configured here can only be referenced from within your task script or process and will not be resolved if they are part of your args, command, or other task attributes.
• runOptions: Defines when and how a task is run.
• hide: Hides the task from the Run Task Quick Pick, which can be useful for elements of a compound task that are not independently runnable.

You can see the full set of task properties and values with IntelliSense in yourtasks.json file. Bring up suggestions withTrigger Suggest (⌃Space (Windows, LinuxCtrl+Space)) and read the descriptions on hover or with theRead More... ('i') flyout.

You can also review thetasks.json schema.

Shell commands need special treatment when it comes to commands and arguments that contain spaces or other special characters like$. By default, the task system supports the following behavior:

• If a single command is provided, the task system passes the command as is to the underlying shell. If the command needs quoting or escaping to function properly, the command needs to contain the proper quotes or escape characters. For example, to list the directory of a folder containing spaces in its name, the command executed in bash should look like this:ls 'folder with spaces'.

{  "label":"dir",  "type":"shell",  "command":"dir 'folder with spaces'"}

• If a command and arguments are provided, the task system will use single quotes if the command or arguments contain spaces. Forcmd.exe, double quotes are used. A shell command like below will be executed in PowerShell asdir 'folder with spaces'.

{  "label":"dir",  "type":"shell",  "command":"dir",  "args": ["folder with spaces"]}

• If you want to control how the argument is quoted, the argument can be a literal specifying the value and a quoting style. The example below uses escaping instead of quoting for an argument with spaces.

{  "label":"dir",  "type":"shell",  "command":"dir",  "args": [    {      "value":"folder with spaces",      "quoting":"escape"    }  ]}

Besides escaping, the following values are supported:

• strong: Uses the shell's strong quoting mechanism, which suppresses all evaluations inside the string. Under PowerShell and for shells under Linux and macOS, single quotes are used ('). For cmd.exe," is used.
• weak: Uses the shell's weak quoting mechanism, which still evaluates expression inside the string (for example, environment variables). Under PowerShell and for shells under Linux and macOS, double quotes are used ("). cmd.exe doesn't support weak quoting so VS Code uses" as well.

If the command itself contains spaces, VS Code will by default strong quote the command as well. As with arguments, the user can control the quoting of the command using the same literal style.

There are more task properties to configure your workflow. You can use IntelliSense with⌃Space (Windows, LinuxCtrl+Space) to get an overview of the valid properties.

In addition to the global menu bar, task commands can be accessed using theCommand Palette (⇧⌘P (Windows, LinuxCtrl+Shift+P)). You can filter on 'task' and can see the various task related commands.

Compound tasks

You can also compose tasks out of simpler tasks with thedependsOn property. For example, if you have a workspace with a client and server folder and both contain a build script, you can create a task that starts both build scripts in separate terminals. If you list more than one task in thedependsOn property, they are executed in parallel by default.

Thetasks.json file looks like this:

{  "version":"2.0.0",  "tasks": [    {      "label":"Client Build",      "command":"gulp",      "args": ["build"],      "options": {        "cwd":"${workspaceFolder}/client"      }    },    {      "label":"Server Build",      "command":"gulp",      "args": ["build"],      "options": {        "cwd":"${workspaceFolder}/server"      }    },    {      "label":"Build",      "dependsOn": ["Client Build","Server Build"]    }  ]}

If you specify"dependsOrder": "sequence", then your task dependencies are executed in the order they are listed independsOn. Any background/watch tasks used independsOn with"dependsOrder": "sequence" must have a problem matcher that tracks when they are "done". The following task runs task Two, task Three, and then task One.

{  "label":"One",  "type":"shell",  "command":"echo Hello ",  "dependsOrder":"sequence",  "dependsOn": ["Two","Three"]}

User level tasks

You can create user level tasks that are not tied to a specific workspace or folder using theTasks: Open User Tasks command. Onlyshell andprocess tasks can be used here since other task types require workspace information.

Output behavior

Sometimes you want to control how the Integrated Terminal panel behaves when running tasks. For instance, you may want to maximize editor space and only look at task output if you think there is a problem. The behavior of the terminal can be controlled using thepresentation property of a task. It offers the following properties:

• reveal: Controls whether the Integrated Terminal panel is brought to front. Valid values are:
  • always - The panel is always brought to front. This is the default.
  • never - The user must explicitly bring the terminal panel to the front using theView >Terminal command (⌃` (Windows, LinuxCtrl+`)).
  • silent - The terminal panel is brought to front only if the output is not scanned for errors and warnings.
• revealProblems: Controls whether the Problems panel is revealed when running this task or not. Takes precedence over optionreveal. Default isnever.
  • always - Always reveals the Problems panel when this task is executed.
  • onProblem - Only reveals the Problems panel if a problem is found.
  • never - Never reveals the Problems panel when this task is executed.
• focus: Controls whether the terminal is taking input focus or not. Default isfalse.
• echo: Controls whether the executed command is echoed in the terminal. Default istrue.
• showReuseMessage: Controls whether to show the "Terminal will be reused by tasks, press any key to close it" message.
• panel: Controls whether the terminal instance is shared between task runs. Possible values are:
  • shared - The terminal is shared and the output of other task runs are added to the same terminal.
  • dedicated - The terminal is dedicated to a specific task. If that task is executed again, the terminal is reused. However, the output of a different task is presented in a different terminal.
  • new - Every execution of that task is using a new clean terminal.
• clear: Controls whether the terminal is cleared before this task is run. Default isfalse.
• close: Controls whether the terminal the task runs in is closed when the task exits. Default isfalse.
• group: Controls whether the task is executed in a specific terminal group using split panes. Tasks in the same group (specified by a string value) will use split terminals to present instead of a new terminal panel.

You can modify the terminal panel behavior for auto-detected tasks as well. For example, if you want to change the output behavior for thenpm: run lint from the ESLint example from above, add thepresentation property to it:

{  // See https://go.microsoft.com/fwlink/?LinkId=733558  // for the documentation about the tasks.json format  "version":"2.0.0",  "tasks": [    {      "type":"npm",      "script":"lint",      "problemMatcher": ["$eslint-stylish"],      "presentation": {        "reveal":"never"      }    }  ]}

You can also mix custom tasks with configurations for detected tasks. Atasks.json that configures thenpm: run lint task and adds a customRun Test tasks looks like this:

{  // See https://go.microsoft.com/fwlink/?LinkId=733558  // for the documentation about the tasks.json format  "version":"2.0.0",  "tasks": [    {      "type":"npm",      "script":"lint",      "problemMatcher": ["$eslint-stylish"],      "presentation": {        "reveal":"never"      }    },    {      "label":"Run tests",      "type":"shell",      "command":"./scripts/test.sh",      "windows": {        "command":".\\scripts\\test.cmd"      },      "group":"test",      "presentation": {        "reveal":"always",        "panel":"new"      }    }  ]}

Run behavior

You can specify a task's run behaviors using therunOptions property:

• reevaluateOnRerun: Controls how variables are evaluated when a task is executed through theRerun Last Task command. The default istrue, meaning that variables will be reevaluated when a task is rerun. When set tofalse the resolved variable values from the previous run of the task will be used.
• runOn: Specifies when a task is run.
  • default - The task will only be run when executed through theRun Task command.
  • folderOpen - The task will be run when the containing folder is opened. The first time you open a folder that contains a task withfolderOpen, you will be asked if you want to allow tasks to run automatically in that folder. You can change your decision later using theManage Automatic Tasks command and selecting betweenAllow Automatic Tasks andDisallow Automatic Tasks.
• instanceLimit - The number of instances of the task that are allowed to run simultaneously. The default value is1.

Customizing auto-detected tasks

As mentioned above, you can customize auto-detected tasks in thetasks.json file. You usually do so to modify presentation properties or to attach a problem matcher to scan the task's output for errors and warnings. You can customize a task directly from theRun Task list by pressing the gear icon to the right to insert the corresponding task reference into thetasks.json file. Assume you have the following Gulp file to lint JavaScript files using ESLint (the file is taken fromhttps://github.com/adametry/gulp-eslint):

const gulp =require('gulp');const eslint =require('gulp-eslint');gulp.task('lint', ()=> {  // ESLint ignores files with "node_modules" paths.  // So, it's best to have gulp ignore the directory as well.  // Also, Be sure to return the stream from the task;  // Otherwise, the task may end before the stream has finished.  return (    gulp      .src(['**/*.js','!node_modules/**'])      // eslint() attaches the lint output to the "eslint" property      // of the file object so it can be used by other modules.      .pipe(eslint())      // eslint.format() outputs the lint results to the console.      // Alternatively use eslint.formatEach() (see Docs).      .pipe(eslint.format())      // To have the process exit with an error code (1) on      // lint error, return the stream and pipe to failAfterError last.      .pipe(eslint.failAfterError())  );});gulp.task('default', ['lint'],function() {  // This will only run if the lint task is successful...});

ExecutingRun Task from the globalTerminal menu will show the following picker:

Press the gear icon. This will create the followingtasks.json file:

{  // See https://go.microsoft.com/fwlink/?LinkId=733558  // for the documentation about the tasks.json format  "version":"2.0.0",  "tasks": [    {      "type":"gulp",      "task":"default",      "problemMatcher": []    }  ]}

Usually you would now add a problem matcher (in this case$eslint-stylish) or modify the presentation settings.

Processing task output with problem matchers

VS Code can process the output from a task with a problem matcher. Problem matchers scan the task output text for known warning or error strings, and report these inline in the editor and in the Problems panel. VS Code ships with several problem matchers 'in-the-box':

• TypeScript:$tsc assumes that file names in the output are relative to the opened folder.
• TypeScript Watch:$tsc-watch matches problems reported from thetsc compiler when executed in watch mode.
• JSHint:$jshint assumes that file names are reported as an absolute path.
• JSHint Stylish:$jshint-stylish assumes that file names are reported as an absolute path.
• ESLint Compact:$eslint-compact assumes that file names in the output are relative to the opened folder.
• ESLint Stylish:$eslint-stylish assumes that file names in the output are relative to the opened folder.
• Go:$go matches problems reported from thego compiler. Assumes that file names are relative to the opened folder.
• CSharp and VB Compiler:$mscompile assumes that file names are reported as an absolute path.
• Lessc compiler:$lessc assumes that file names are reported as absolute path.
• Node Sass compiler:$node-sass assumes that file names are reported as an absolute path.

You can also create your own problem matcher, which we'll discussin a later section.

Binding keyboard shortcuts to tasks

If you need to run a task frequently, you can define a keyboard shortcut for the task.

For example, to bindCtrl+H to theRun tests task from above, add the following to yourkeybindings.json file:

{  "key":"ctrl+h",  "command":"workbench.action.tasks.runTask",  "args":"Run tests"}

Variable substitution

When authoring tasks configurations, it is useful to have a set of predefined common variables such as the active file (${file}) or workspace root folder (${workspaceFolder}). VS Code supports variable substitution inside strings in thetasks.json file and you can see a full list of predefined variables in theVariables Reference.

Note: Not all properties will accept variable substitution. Specifically, onlycommand,args, andoptions support variable substitution.

Below is an example of a custom task configuration that passes the current opened file to the TypeScript compiler.

{  "label":"TypeScript compile",  "type":"shell",  "command":"tsc ${file}",  "problemMatcher": ["$tsc"]}

Similarly, you can reference your project's configuration settings by prefixing the name with${config:. For example,${config:python.formatting.autopep8Path} returns the Python extension settingformatting.autopep8Path.

Below is an example of a custom task configuration, which executes autopep8 on the current file using the autopep8 executable defined by thepython.formatting.autopep8Path setting:

{  "label":"autopep8 current file",  "type":"process",  "command":"${config:python.formatting.autopep8Path}",  "args": ["--in-place","${file}"]}

If you want to specify the selected Python interpreter used by the Python extension fortasks.json orlaunch.json, you can use the${command:python.interpreterPath} command.

If simple variable substitution isn't enough, you can also get input from the user of your task by adding aninputs section to yourtasks.json file.

For more information aboutinputs, see theVariables Reference.

Operating system specific properties

The task system supports defining values (for example, the command to be executed) specific to an operating system. To do so, put an operating system specific literal into thetasks.json file and specify the corresponding properties inside that literal.

Below is an example that uses the Node.js executable as a command and is treated differently on Windows and Linux:

{  "label":"Run Node",  "type":"process",  "windows": {    "command":"C:\\Program Files\\nodejs\\node.exe"  },  "linux": {    "command":"/usr/bin/node"  }}

Valid operating properties arewindows for Windows,linux for Linux, andosx for macOS. Properties defined in an operating system specific scope override properties defined in the task or global scope.

Global tasks

Task properties can also be defined in the global scope. If present, they will be used for specific tasks unless they define the same property with a different value. In the example below, there is a globalpresentation property, which defines that all tasks should be executed in a new panel:

{  // See https://go.microsoft.com/fwlink/?LinkId=733558  // for the documentation about the tasks.json format  "version":"2.0.0",  "presentation": {    "panel":"new"  },  "tasks": [    {      "label":"TS - Compile current file",      "type":"shell",      "command":"tsc ${file}",      "problemMatcher": ["$tsc"]    }  ]}

Tip: To get access to the global scopetasks.json file, open the Command Palette (⇧⌘P (Windows, LinuxCtrl+Shift+P)) and run theTasks: Open User Tasks command.

Character escaping in PowerShell

When the default shell is PowerShell, or when a task is configured to use PowerShell, you might see unexpected space and quote escaping. The unexpected escaping only occurs with cmdlets because VS Code doesn't know if your command contains cmdlets. Example 1 below shows a case where you'll get escaping that doesn't work with PowerShell. Example 2 shows the best, cross-platform, way to get good escaping. In some cases, you might not be able to follow example 2 and you'll need to do the manual escaping shown in example 3.

"tasks": [    {        "label":"PowerShell example 1 (unexpected escaping)",        "type":"shell",        "command":"Get-ChildItem\"Folder With Spaces\""    },    {        "label":"PowerShell example 2 (expected escaping)",        "type":"shell",        "command":"Get-ChildItem",        "args": ["Folder With Spaces"]    },    {        "label":"PowerShell example 3 (manual escaping)",        "type":"shell",        "command":"& Get-ChildItem\\\"Folder With Spaces\\\""    }]

Changing the encoding for a task output

Tasks frequently act with files on disk. If these files are stored on disk with an encoding different than the system encoding, you need to let the command executed as a task know which encoding to use. Since this depends on the operating system and the shell used, there is no general solution to control this. Below are advice and examples on how to make it work.

If you need to tweak the encoding, you should check whether it makes sense to change the default encoding used by your operating system or at least change it for the shell you use by tweaking the shell's profile file.

If you only need to tweak it for a specific task, then add the OS-specific command necessary to change the encoding to the tasks command line. The following example is for Windows using code page of 437 as its default. The task shows the output of a file containing Cyrillic characters and therefore needs code page 866. The task to list the file looks like this assuming that the default shell is set tocmd.exe:

{  // See https://go.microsoft.com/fwlink/?LinkId=733558  // for the documentation about the tasks.json format  "version":"2.0.0",  "tasks": [    {      "label":"more",      "type":"shell",      "command":"chcp 866 && more russian.txt",      "problemMatcher": []    }  ]}

If the task is executed inPowerShell, the command needs to read like thischcp 866; more russian.txt. On Linux and macOS, thelocale command can be used to inspect the locale and tweak the necessary environment variables.

Examples of tasks in action

To highlight the power of tasks, here are a few examples of how VS Code can use tasks to integrate external tools like linters and compilers.

Transpiling TypeScript to JavaScript

TheTypeScript topic includes an example that creates a task to transpile TypeScript to JavaScript and observe any related errors from within VS Code.

Transpiling Less and SCSS into CSS

The CSS topic provides examples of how to use Tasks to generate CSS files.

1. Manually transpiling with a Build task
2. Automation of the compile step with a file watcher

Defining a problem matcher

VS Code ships some of the most common problem matchers 'in-the-box'. However, there are lots of compilers and linting tools out there, all of which produce their own style of errors and warnings so you may want to create your own problem matcher.

We have ahelloWorld.c program in which the developer mistypedprintf asprinft. Compiling it withgcc will produce the following warning:

helloWorld.c:5:3: warning: implicit declaration of function ‘prinft’

We want to produce a problem matcher that can capture the message in the output and show a corresponding problem in VS Code. Problem matchers heavily rely onregular expressions. The section below assumes you are familiar with regular expressions.

Tip: We have found theRegEx101 playground, which has an ECMAScript (JavaScript) flavor, to be a great way to develop and test regular expressions.

A matcher that captures the above warning (and errors) looks like this:

{  // The problem is owned by the cpp language service.  "owner":"cpp",  // The file name for reported problems is relative to the opened folder.  "fileLocation": ["relative","${workspaceFolder}"],  // The name that will be shown as the source of the problem.  "source":"gcc",  // The actual pattern to match problems in the output.  "pattern": {    // The regular expression. Example to match: helloWorld.c:5:3: warning: implicit declaration of function ‘printf’ [-Wimplicit-function-declaration]    "regexp":"^(.*):(\\d+):(\\d+):\\s+(warning|error):\\s+(.*)$",    // The first match group matches the file name which is relative.    "file":1,    // The second match group matches the line on which the problem occurred.    "line":2,    // The third match group matches the column at which the problem occurred.    "column":3,    // The fourth match group matches the problem's severity. Can be ignored. Then all problems are captured as errors.    "severity":4,    // The fifth match group matches the message.    "message":5  }}

Note that the file, line, and message properties are mandatory. ThefileLocation specifies whether the file paths that are produced by the task output and matched in the problem areabsolute orrelative. If the task produces both absolute and relative paths, you can use theautoDetect file location. WithautoDetect, paths are first tested as absolute paths, and if the file doesn't exist then the path is assumed to be relative.

Theseverity specifies which problem severity to use if the pattern doesn't include one. The possible values forseverity areerror,warning, orinfo.

Here is a finishedtasks.json file with the code above (comments removed) wrapped with the actual task details:

{  "version":"2.0.0",  "tasks": [    {      "label":"build",      "command":"gcc",      "args": ["-Wall","helloWorld.c","-o","helloWorld"],      "problemMatcher": {        "owner":"cpp",        "fileLocation": ["relative","${workspaceFolder}"],        "source":"gcc",        "pattern": {          "regexp":"^(.*):(\\d+):(\\d+):\\s+(warning|error):\\s+(.*)$",          "file":1,          "line":2,          "column":3,          "severity":4,          "message":5        }      }    }  ]}

Running it inside VS Code and pressing⇧⌘M (Windows, LinuxCtrl+Shift+M) to get the list of problems gives you the following output:

Note: TheC/C++ extension includes problem matchers for GCC so there is no need to define our own.

There are a couple more properties that can be used inside a pattern. These are:

• location - If the problem location is line or line,column or startLine,startColumn,endLine,endColumn, then our generic location match group can be used.
• endLine - The match group index for the problem's end line. Can be omitted if no end line value is provided by the compiler.
• endColumn - The match group index for the problem's end column. Can be omitted if no end column value is provided by the compiler.
• code - The match group index for the problem's code. Can be omitted if no code value is provided by the compiler.

You can also define a problem matcher that captures only a file. To do so, define apattern with the optionalkind attribute set tofile. In this case, there is no need to provide aline orlocation property.

Note: A functional pattern must at least provide a match group forfile andmessage if thekind property is set tofile. If nokind property is provided or thekind property is set tolocation, a function pattern must provide aline orlocation property as well.

Note: The problem matcher only parses output from the given command. If you want to parse output written to separate file (e.g. a log file), make the command that you run print out lines from the separate file before it finishes executing.

Defining a multiline problem matcher

Some tools spread problems found in a source file over several lines, especially if stylish reporters are used. An example isESLint; in stylish mode it produces output like this:

test.js  1:0   error  Missing "use strict" statement                 strict✖ 1 problems (1errors, 0 warnings)

Our problem matcher is line-based so we need to capture the file name (test.js) with a different regular expression than the actual problem location and message (1:0 error Missing "use strict" statement).

To do this, use an array of problem patterns for thepattern property. This way you define a pattern per each line you want to match.

The following problem pattern matches the output from ESLint in stylish mode - but still has one small issue that we need to resolve next. The code below has a first regular expression to capture the file name and the second to capture the line, column, severity, message, and error code:

{  "owner":"javascript",  "fileLocation": ["relative","${workspaceFolder}"],  "pattern": [    {      "regexp":"^([^\\s].*)$",      "file":1    },    {      "regexp":"^\\s+(\\d+):(\\d+)\\s+(error|warning|info)\\s+(.*)\\s\\s+(.*)$",      "line":1,      "column":2,      "severity":3,      "message":4,      "code":5    }  ]}

However, this pattern will not work if there is more than one problem on a resource. For instance, imagine the following output from ESLint:

test.js  1:0   error  Missing "use strict" statement                 strict  1:9   error  foo is defined but never used                  no-unused-vars  2:5   error  x is defined but never used                    no-unused-vars  2:11  error  Missing semicolon                              semi  3:1   error  "bar" is not defined                           no-undef  4:1   error  Newline required at end of file but not found  eol-last✖ 6 problems (6errors, 0 warnings)

The pattern's first regular expression will match "test.js", the second "1:0 error ...". The next line "1:9 error ..." is processed but not matched by the first regular expression and so no problem is captured.

To make this work, the last regular expression of a multiline pattern can specify theloop property. If set to true, it instructs the task system to apply the last pattern of a multiline matcher to the lines in the output as long as the regular expression matches.

The information captured by the first pattern, which in this case matchestest.js, will be combined with each of the subsequent lines that match theloop pattern to create multiple problems. In this example, six problems would be created.

Here is a problem matcher to fully capture ESLint stylish problems:

{  "owner":"javascript",  "fileLocation": ["relative","${workspaceFolder}"],  "pattern": [    {      "regexp":"^([^\\s].*)$",      "file":1    },    {      "regexp":"^\\s+(\\d+):(\\d+)\\s+(error|warning|info)\\s+(.*)\\s\\s+(.*)$",      "line":1,      "column":2,      "severity":3,      "message":4,      "code":5,      "loop":true    }  ]}

Note: If you have multiple problems that occur on the same resource with the exact same line and column, then only one problem will be shown. This applies to all problem matchers, not just multiline problem matchers.

Modifying an existing problem matcher

If an existing problem matcher is close to what you need, you can modify it in yourtasks.json task. For example, the$tsc-watch problem matcher only applies to closed documents. If you want to have it apply to all documents you can modify it:

{  "type":"npm",  "script":"watch",  "problemMatcher": {    "base":"$tsc-watch",    "applyTo":"allDocuments"  },  "isBackground":true}

Other modifiable problem matcher properties includebackground,fileLocation,owner,pattern,severity, andsource.

Background / watching tasks

Some tools support running in the background while watching the file system for changes and then triggering an action when a file changes on disk. WithGulp such functionality is provided through the npm modulegulp-watch. The TypeScript compilertsc has built in support for this via the--watch command line option.

To provide feedback that a background task is active in VS Code and producing problem results, a problem matcher has to use additional information to detect thesestate changes in the output. Let's take thetsc compiler as an example. When the compiler is started in watch mode, it prints the following additional information to the console:

> tsc --watch12:30:36 PM - Compilation complete. Watching for file changes.

When a file changes on disk that contains a problem, the following output appears:

12:32:35 PM - File change detected. Starting incremental compilation...src/messages.ts(276,9): error TS2304: Cannot find name'candidate'.12:32:35 PM - Compilation complete. Watching for file changes.

Looking at the output shows the following pattern:

• The compiler runs whenFile change detected. Starting incremental compilation... is printed to the console.
• The compiler stops whenCompilation complete. Watching for file changes. is printed to the console.
• Between those two strings problems are reported.
• The compiler also runs once the initial start (without printingFile change detected. Starting incremental compilation... to the console).

To capture this information, a problem matcher can provide abackground property.

For thetsc compiler, an appropriatebackground property looks like this:

"background": {    "activeOnStart":true,    "beginsPattern":"^\\s*\\d{1,2}:\\d{1,2}:\\d{1,2}(?: AM| PM)? - File change detected\\. Starting incremental compilation\\.\\.\\.",    "endsPattern":"^\\s*\\d{1,2}:\\d{1,2}:\\d{1,2}(?: AM| PM)? - Compilation complete\\. Watching for file changes\\."}

In addition to thebackground property on the problem matcher, the task itself has to be marked asisBackground so that the task keeps running in the background.

A full handcraftedtasks.json for atsc task running in watch mode looks like this:

{  "version":"2.0.0",  "tasks": [    {      "label":"watch",      "command":"tsc",      "args": ["--watch"],      "isBackground":true,      "problemMatcher": {        "owner":"typescript",        "fileLocation":"relative",        "pattern": {          "regexp":"^([^\\s].*)\\((\\d+|\\d+,\\d+|\\d+,\\d+,\\d+,\\d+)\\):\\s+(error|warning|info)\\s+(TS\\d+)\\s*:\\s*(.*)$",          "file":1,          "location":2,          "severity":3,          "code":4,          "message":5        },        "background": {          "activeOnStart":true,          "beginsPattern":"^\\s*\\d{1,2}:\\d{1,2}:\\d{1,2}(?: AM| PM)? - File change detected\\. Starting incremental compilation\\.\\.\\.",          "endsPattern":"^\\s*\\d{1,2}:\\d{1,2}:\\d{1,2}(?: AM| PM)? - Compilation complete\\. Watching for file changes\\."        }      }    }  ]}

Next steps

That was tasks - let's keep going...

• tasks.json Schema - You can review the fulltasks.json schema and descriptions.
• Basic Editing - Learn about the powerful VS Code editor.
• Code Navigation - Move quickly through your source code.
• Language Support - Learn about our supported programming languages, both shipped with VS Code and through community extensions.
• Debugging - Debug your source code directly in the VS Code editor.

Common questions

Can a task use a different shell than the one specified for the Integrated Terminal?

Yes. You can use the"terminal.integrated.automationProfile.*" setting to set the shell that will be used for all automation in VS Code, which includes Tasks.

    "terminal.integrated.automationProfile.windows": {        "path":"cmd.exe"    }

Alternatively, you can override a task's shell with theoptions.shell property. You can set this per task, globally, or per platform. For example, to use cmd.exe on Windows, yourtasks.json would include:

{    "version":"2.0.0",    "windows": {        "options": {            "shell": {                "executable":"cmd.exe",                "args": [                    "/d","/c"                ]            }        }    },    ...

Can a background task be used as aprelaunchTask in launch.json?

Yes. Since a background task will run until killed, a background task on its own has no signal that it has "completed". To use a background task as aprelaunchTask, you must add an appropriate backgroundproblemMatcher to the background task so that there is a way for the task system and debug system to know that the task "finished".

Your task could be:

{  "type":"npm",  "script":"watch",  "problemMatcher":"$tsc-watch",  "isBackground":true}

Note: The$tsc-watch is abackground problem matcher, as is required for a background task.

You can then use the task as aprelaunchTask in yourlaunch.json file:

{  "name":"Launch Extension",  "type":"extensionHost",  "request":"launch",  "runtimeExecutable":"${execPath}",  "args": ["--extensionDevelopmentPath=${workspaceRoot}"],  "stopOnEntry":false,  "sourceMaps":true,  "outFiles": ["${workspaceRoot}/out/src/**/*.js"],  "preLaunchTask":"npm: watch"}

For more on background tasks, go toBackground / watching tasks.

Why do I get "command not found" when running a task?

The message "command not found" happens when the task command you're trying to run is not recognized by your terminal as something runnable. Most often, this occurs because the command is configured as part of your shell's startup scripts. Tasks are run as non-login and non-interactive, which means that the startup scripts for your shell won't be run.nvm in particular is known to use startup scripts as part of its configuration.

There are several ways to resolve this issue:

1. Make sure your command is on your path and doesn't require startup scripts to get added to your path. This is the most thorough way to solve the problem, and is the recommended solution.
2. You can make a one-off fix for your task to run as login or interactive. This is not recommended, as it can have other consequences. However, it can also be a quick and easy fix for a single task. Below is an example of a task that does this withbash as the shell:

{  "type":"npm",  "script":"watch",  "options": {    "shell": {      "args": ["-c","-l"]    }  }}

The abovenpm task will runbash with a command (-c), just like the tasks system does by default. However, this task also runsbash as a login shell (-l).