VS Code supports variable substitution inside strings in launch.json and has the following predefined variables:

• ${workspaceFolder} - the path of the folder opened in VS Code
• ${workspaceRootFolderName} - the name of the folder opened in VS Code without any slashes (/)
• ${file} - the current opened file
• ${relativeFile} - the current opened file relative to workspaceRoot
• ${fileBasename} - the current opened file's basename
• ${fileBasenameNoExtension} - the current opened file's basename with no file extension
• ${fileDirname} - the current opened file's dirname
• ${fileExtname} - the current opened file's extension
• ${cwd} - the task runner's current working directory on startup
• ${lineNumber} - the current selected line number in the active file

You can also reference environment variables through ${env:Name} syntax (for example, ${env:PATH}). Be sure to match the environment variable name's casing, for example ${env:Path} on Windows.

{
    "type": "node",
    "request": "launch",
    "name": "Launch Program",
    "program": "${workspaceFolder}/app.js",
    "cwd": "${workspaceFolder}",
    "args": [ "${env:USERNAME}" ]
}

You can reference VS Code settings and commands using the following syntax:

• ${config:Name} - example: ${config:editor.fontSize}
• ${command:CommandID} - example: ${command:explorer.newFolder}

在vscode中定义了一些变量，在配置任务脚本时，可能会用到。本文以launch.json脚本为例，介绍各个变量的含义。

假设当前workspace的路径为:"C:UsersadminDesktop est"，workspace文件夹下的结构如下（+表示下一层）：

C:UsersadminDesktop est

+.vscode

  ++tasks.json

  ++launch.json

+main.cpp

${workspaceFolder} :表示当前workspace文件夹路径，也即C:UsersadminDesktop est

${workspaceRootFolderName}:表示workspace的文件夹名，也即test

${file}:文件自身的绝对路径，也即C:UsersadminDesktop est.vscodelaunch.json

${relativeFile}:文件在workspace中的路径，也即.vscodelaunch.json

${fileBasenameNoExtension}:当前文件的文件名，不带后缀，也即launch

${fileBasename}:当前文件的文件名，launch.json

${fileDirname}:文件所在的文件夹路径，也即C:UsersadminDesktop est.vscode

${fileExtname}:当前文件的后缀，也即.json

${lineNumber}:当前文件光标所在的行号

${env:PATH}:系统中的环境变量
 

更新一个链接：https://code.visualstudio.com/docs/editor/variables-reference