VSCode tasks.json中的各种替换变量的意思 ${workspaceFolder} ${file} ${fileBasename} ${fileDirname}等

When authoring tasks configurations, it is often useful to have a set of predefined common variables. VS Code supports variable substitution inside strings in the 

tasks.json

 file
and has the following predefined variables:
${workspaceFolder} the path of the workspace folder that contains the tasks.json file
${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 the workspace folder containing the file
${fileBasename} the current opened file's basename
${fileBasenameNoExtension} the current opened file's basename without the 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} (for example, ${env:PATH}). Be sure to match the environment
variable name's casing, for example 

${env:Path}

 on Windows.

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

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

}

部分翻译：（来自互联网）

${workspaceRoot}
当前打开的文件夹的绝对路径+文件夹的名字

            ${workspaceRootFolderName}
  当前打开的文件夹的名字

 
  ${file}当前打开正在编辑的文件名，包括绝对路径，文件名，文件后缀名

${relativeFile}从当前打开的文件夹到当前打开的文件的路径 

如
当前打开的是test文件夹，当前的打开的是main.c，并有test / first / second / main.c

那么此变量代表的是
 first / second / main.c

${fileBasename} 
当前打开的文件名+后缀名，不包括路径

${fileBasenameNoExtension}
当前打开的文件的文件名，不包括路径和后缀名

${fileDirname}
当前打开的文件所在的绝对路径，不包括文件名

${fileExtname}
当前打开的文件的后缀名

${cwd}
the task runner's current working directory on startup

不知道怎么描述，这是原文解释，

跟
cmd 里面的 cwd 是一样的

${lineNumber} 
当前打开的文件，光标所在的行数