dotnet script
Run C# scripts from the .NET CLI, define NuGet packages inline and edit/debug them in VS Code - all of that with full language services support from OmniSharp.
⚠️ If you are using C# for VS Code version 1.15.0 on Linux or Mac, make sure to update to 1.15.2. There is a bug in the version of OmniSharp that shipped with 1.15.0, that prevents C# scripting from working in non-Windows environments. You can also go to VS Code settings and set"omnisharp.path":"latest"
. This change will allow you to use C# 7.3 already.
Build status
Build server | Platform | Build status |
---|---|---|
AppVeyor | Windows | |
Travis | Linux / OS X |
Nuget Packages
Installing
Prerequisites
The only thing we need to install is .Net Core 2.1+ SDK.
.Net Core 2.1 Global Tool
.Net Core 2.1 introduces the concept of global tools meaning that you can install dotnet-script
using nothing but the .NET CLI.
dotnet tool install -g dotnet-script
You can invoke the tool using the following command: dotnet-script
Tool 'dotnet-script' (version '0.22.0') was successfully installed.
The advantage of this approach is that you can use the same command for installation across all platforms.
⚠️ In order to use the global tool you need .Net Core SDK 2.1.300 or higher. The earlier previews and release candidates of .NET Core 2.1 are not supported.
.NET Core SDK also supports viewing a list of installed tools and their uninstallation.
dotnet tool list -g
Package Id Version Commands
---------------------------------------------
dotnet-script 0.22.0 dotnet-script
dotnet tool uninstall dotnet-script -g
Tool 'dotnet-script' (version '0.22.0') was successfully uninstalled.
Windows
choco install dotnet.script
We also provide a PowerShell script for installation.
(new-object Net.WebClient).DownloadString("https://raw.githubusercontent.com/filipw/dotnet-script/master/install/install.ps1") | iex
Linux and Mac
curl -s https://raw.githubusercontent.com/filipw/dotnet-script/master/install/install.sh | bash
If permission is denied we can try with sudo
curl -s https://raw.githubusercontent.com/filipw/dotnet-script/master/install/install.sh | sudo bash
Docker
A Dockerfile for running dotnet-script in a Linux container is available. Build:
cd build
docker build -t dotnet-script -f Dockerfile ..
And run:
docker run -it dotnet-script --version
Github
You can manually download all the releases in zip
format from the Github releases page.
Usage
Our typical helloworld.csx
might look like this:
Console.WriteLine("Hello world!");
That is all it takes and we can execute the script. Args are accessible via the global Args array.
dotnet script helloworld.csx
Scaffolding
Simply create a folder somewhere on your system and issue the following command.
dotnet script init
This will create main.csx
along with the launch configuration needed to debug the script in VS Code.
.
├── .vscode
│ └── launch.json
├── main.csx
└── omnisharp.json
We can also initialize a folder using a custom filename.
dotnet script init custom.csx
Instead of main.csx
which is the default, we now have a file named custom.csx
.
.
├── .vscode
│ └── launch.json
├── custom.csx
└── omnisharp.json
Note: Executing
dotnet script init
inside a folder that already contains one or more script files will not create themain.csx
file.
Running scripts
Scripts can be executed directly from the shell as if they were executables.
foo.csx arg1 arg2 arg3
OSX/Linux
Just like all scripts, on OSX/Linux you need to have a !# and mark the file as executable via chmod +x foo.csx.
If you use dotnet script init to create your csx it will automatically have the !# directive and be marked as executable.
The OSX/Linux shebang directive should be #!/usr/bin/env dotnet-script
#!/usr/bin/env dotnet-script
Console.WriteLine("Hello world");
You can execute your script using dotnet script or dotnet-script, which allows you to pass arguments to control your script execution more.
foo.csx arg1 arg2 arg3
dotnet script foo.csx -- arg1 arg2 arg3
dotnet-script foo.csx -- arg1 arg2 arg3
Passing arguments to scripts
All arguments after --
are passed to the script in the following way:
dotnet script foo.csx -- arg1 arg2 arg3
Then you can access the arguments in the script context using the global Args
collection:
foreach (var arg in Args)
{
Console.WriteLine(arg);
}
All arguments before --
are processed by dotnet script
. For example, the following command-line
dotnet script -d foo.csx -- -d
will pass the -d
before --
to dotnet script
and enable the debug mode whereas the -d
after --
is passed to script for its own interpretation of the argument.
NuGet Packages
dotnet script
has built-in support for referencing NuGet packages directly from within the script.
#r "nuget: AutoMapper, 6.1.0"
Note: Omnisharp needs to be restarted after adding a new package reference
Package Sources
We can define package sources using a NuGet.Config
file in the script root folder. In addition to being used during execution of the script, it will also be used by OmniSharp
that provides language services for packages resolved from these package sources.
As an alternative to maintaining a local NuGet.Config
file we can define these package sources globally either at the user level or at the computer level as described in Configuring NuGet Behaviour
It is also possible to specify packages sources when executing the script.
dotnet script foo.csx -s https://SomePackageSource
Multiple packages sources can be specified like this:
dotnet script foo.csx -s https://SomePackageSource -s https://AnotherPackageSource
Creating DLLs or Exes from a CSX file
Dotnet-Script can create a standalone executable or DLL for your script.
Switch | Long switch | description |
---|---|---|
-o | --output | Directory where the published executable should be placed. Defaults to a 'publish' folder in the current directory. |
-n | --name | The name for the generated DLL (executable not supported at this time). Defaults to the name of the script. |
--dll | Publish to a .dll instead of an executable. | |
-c | --configuration | Configuration to use for publishing the script [Release/Debug]. Default is "Debug" |
-d | --debug | Enables debug output. |
-r | --runtime | The runtime used when publishing the self contained executable. Defaults to your current runtime. |
The executable you can run directly independent of dotnet install, while the DLL is can be run using the dotnet CLI like this:
dotnet publish\myscript.dll -- arg1 arg2
DLL Cache
Dotnet-Script will automatically create a DLL on first execution of a script and as long as the source code has not changed it will continue to use that DLL significantlly speeding up the execution of your scripts (by 8x). The cached DLL's are stored in the user %tmp%/dotnet-script folder.
You can override this a automatic caching by passing --nocache flag, which will cause your script to be dynamically compiled everytime you run it.
Debugging
The days of debugging scripts using Console.WriteLine
are over. One major feature of dotnet script
is the ability to debug scripts directly in VS Code. Just set a breakpoint anywhere in your script file(s) and hit F5(start debugging)
Script Packages
Script packages are a way of organizing reusable scripts into NuGet packages that can be consumed by other scripts. This means that we now can leverage scripting infrastructure without the need for any kind of bootstrapping.
Creating a script package
A script package is just a regular NuGet package that contains script files inside the content
or contentFiles
folder.
The following example shows how the scripts are laid out inside the NuGet package according to the standard convention .
└── contentFiles
└── csx
└── netstandard2.0
└── main.csx
This example contains just the main.csx
file in the root folder, but packages may have multiple script files either in the root folder or in subfolders below the root folder.
When loading a script package we will look for an entry point script to be loaded. This entry point script is identified by one of the following.
- A script called
main.csx
in the root folder - A single script file in the root folder
If the entry point script cannot be determined, we will simply load all the scripts files in the package.
The advantage with using an entry point script is that we can control loading other scripts from the package.
Consuming a script package
To consume a script package all we need to do specify the NuGet package in the #load
directive.
The following example loads the simple-targets package that contains script files to be included in our script.
#! "netcoreapp2.1"
#load "nuget:simple-targets-csx, 6.0.0"
using static SimpleTargets;
var targets = new TargetDictionary();
targets.Add("default", () => Console.WriteLine("Hello, world!"));
Run(Args, targets);
Note: Debugging also works for script packages so that we can easily step into the scripts that are brought in using the
#load
directive.
Remote Scripts
Scripts don't actually have to exist locally on the machine. We can also execute scripts that are made available on an http(s)
endpoint.
This means that we can create a Gist on Github and execute it just by providing the URL to the Gist.
This Gist contains a script that prints out "Hello World"
We can execute the script like this
dotnet script https://gist.githubusercontent.com/seesharper/5d6859509ea8364a1fdf66bbf5b7923d/raw/0a32bac2c3ea807f9379a38e251d93e39c8131cb/HelloWorld.csx
That is a pretty long URL, so why don't make it a TinyURL like this:
dotnet script https://tinyurl.com/y8cda9zt
Script Location
A pretty common scenario is that we have logic that is relative to the script path. We don't want to require the user to be in a certain directory for these paths to resolve correctly so here is how to provide the script path and the script folder regardless of the current working directory.
public static string GetScriptPath([CallerFilePath] string path = null) => path;
public static string GetScriptFolder([CallerFilePath] string path = null) => Path.GetDirectoryName(path);
Tip: Put these methods as top level methods in a separate script file and
#load
that file wherever access to the script path and/or folder is needed.
REPL
This release contains a C# REPL (Read-Evaluate-Print-Loop). The REPL mode ("interactive mode") is started by executing dotnet-script
without any arguments.
The interactive mode allows you to supply individual C# code blocks and have them executed as soon as you press Enter. The REPL is configured with the same default set of assembly references and using statements as regular CSX script execution.
Basic usage
Once dotnet-script
starts you will see a prompt for input. You can start typing C# code there.
~$ dotnet script
> var x = 1;
> x+x
2
If you submit an unterminated expression into the REPL (no ;
at the end), it will be evaluated and the result will be serialized using a formatter and printed in the output. This is a bit more interesting than just calling ToString()
on the object, because it attempts to capture the actual structure of the object. For example:
~$ dotnet script
> var x = new List<string>();
> x.Add("foo");
> x
List<string>(1) { "foo" }
> x.Add("bar");
> x
List<string>(2) { "foo", "bar" }
>
Inline Nuget packages
REPL also supports inline Nuget packages - meaning the Nuget packages can be installed into the REPL from within the REPL. This is done via our #r
and #load
from Nuget support and uses identical syntax.
~$ dotnet script
> #r "nuget: Automapper, 6.1.1"
> using AutoMapper;
> typeof(MapperConfiguration)
[AutoMapper.MapperConfiguration]
> #load "nuget: simple-targets-csx, 6.0.0";
> using static SimpleTargets;
> typeof(TargetDictionary)
[Submission#0+SimpleTargets+TargetDictionary]
Multiline mode
Using Roslyn syntax parsing, we also support multiline REPL mode. This means that if you have an uncompleted code block and press Enter, we will automatically enter the multiline mode. The mode is indicated by the *
character. This is particularly useful for declaring classes and other more complex constructs.
~$ dotnet script
> class Foo {
* public string Bar {get; set;}
* }
> var foo = new Foo();
REPL commands
Aside from the regular C# script code, you can invoke the following commands (directives) from within the REPL:
Command | Description |
---|---|
#load |
Load a script into the REPL (same as #load usage in CSX) |
#r |
Load an assembly into the REPL (same as #r usage in CSX) |
#reset |
Reset the REPL back to initial state (without restarting it) |
#cls |
Clear the console screen without resetting the REPL state |
#exit |
Exits the REPL |
Seeding REPL with a script
You can execute a CSX script and, at the end of it, drop yourself into the context of the REPL. This way, the REPL becomes "seeded" with your code - all the classes, methods or variables are available in the REPL context. This is achieved by running a script with an -i
flag.
For example, given the following CSX script:
var msg = "Hello World";
Console.WriteLine(msg);
When you run this with the -i
flag, Hello World
is printed, REPL starts and msg
variable is available in the REPL context.
~$ dotnet script foo.csx -i
Hello World
>
You can also seed the REPL from inside the REPL - at any point - by invoking a #load
directive pointed at a specific file. For example:
~$ dotnet script
> #load "foo.csx"
Hello World
>
Piping
The following example shows how we can pipe data in and out of a script.
The UpperCase.csx
script simply converts the standard input to upper case and writes it back out to standard output.
#! "netcoreapp2.1"
using (var streamReader = new StreamReader(Console.OpenStandardInput()))
{
Write(streamReader.ReadToEnd().ToUpper());
}
We can now simply pipe the output from one command into our script like this.
echo "This is some text" | dotnet script UpperCase.csx
THIS IS SOME TEXT
Debugging
The first thing we need to do add the following to the launch.config
file that allows VS Code to debug a running process.
{
"name": ".NET Core Attach",
"type": "coreclr",
"request": "attach",
"processId": "${command:pickProcess}"
}
To debug this script we need a way to attach the debugger in VS Code and to the simplest thing we can do here is to wait for the debugger to attach by adding this method somewhere.
public static void WaitForDebugger()
{
Console.WriteLine("Attach Debugger (VS Code)");
while(!Debugger.IsAttached)
{
}
}
To debug the script when executing it from the command line we can do something like
#! "netcoreapp2.0"
#r "nuget: NetStandard.Library, 2.0.0"
WaitForDebugger();
using (var streamReader = new StreamReader(Console.OpenStandardInput()))
{
Write(streamReader.ReadToEnd().ToUpper()); // <- SET BREAKPOINT HERE
}
Now when we run the script from the command line we will get
$ echo "This is some text" | dotnet script UpperCase.csx
Attach Debugger (VS Code)
This now gives us a chance to attach the debugger before stepping into the script and from VS Code, select the .NET Core Attach
debugger and pick the process that represents the executing script.
Once that is done we should see out breakpoint being hit.
Configuration(Debug/Release)
By default, scripts will be compiled using the debug
configuration. This is to ensure that we can debug a script in VS Code as well as attaching a debugger for long running scripts.
There are however situations where we might need to execute a script that is compiled with the release
configuration. For instance, running benchmarks using BenchmarkDotNet is not possible unless the script is compiled with the release
configuration.
We can specify this when executing the script.
dotnet script foo.csx -c release