csharp

csharp(1)                    General Commands Manual                   csharp(1)



NAME
       csharp - Interactive C# Shell and Scripting

SYNOPSIS
       csharp [--attach PID] [-e EXPRESSION] [file1 [file2]] [compiler-options]
       [--|-s script-options]

DESCRIPTION
       The csharp command is an interactive C# shell and scripting host that
       allows the user to enter and evaluate C# statements and expressions from
       the command line or execute C# scripts.  The regular mcs command line
       options can be used in this version of the compiler.

       Files specified in the command line will be loaded and executed as
       scripts.

       Starting with Mono 2.10, the csharp command can be used as an interpreter
       executed by executables flagged with the Unix execute attribute.   To do
       this, make the first line of your C# source code look like this:

         #!/usr/bin/csharp
         Console.WriteLine ("Hello, World");

       Starting with Mono 5.0, command line arguments may now be passed to the
       csharp command by specifying either the -s or -- (script) options.

       The -s option is ideal for interpreting executable scripts that utilize
       shebang syntax (introduced in Mono 2.10). This allows command line
       arguments to be passed to and consumed cleanly by the script:

         #!/usr/bin/csharp -s
         foreach (var arg in Args)
           Console.WriteLine ($"script argument: {arg}");

OPTIONS
       The commands accept all of the commands that are available to the mcs
       command, so you can reference assemblies, specify paths, language level
       and so on from the command line.   In addition, the following command
       line options are supported:

       -s SCRIPT_FILE
              This option is ideal for authoring executable scripts that utilize
              the Unix shebang feature. Unix will implicitly append as an
              argument the path of the script to execute. When the executable is
              invoked, any arguments then passed to it will be available in the
              Args global. Example: #!/usr/bin/env csharp -s

       --     Any arguments that follow will not be passed to the compiler
              driver, and instead will be made available in the Args global.
              Example: csharp -- a b c will result in Args = { "a", "b", "c" }
              in the interactive shell.

       --attach
              This is an advanced option and should only be used if you have a
              deep understanding of multi-threading.     This option is availble
              on the csharp command and allows the compiler to be injected into
              other processes.  This is done by injecting the C# shell in a
              separate thread that runs concurrently with your application.
              This means that you must take special measures to avoid crashing
              the target application while using it.  For example, you might
              have to take the proper locks before issuing any commands that
              might affect the target process state, or sending commands through
              a method dispatcher.

       -e EXPRESSION
              This will evaluate the specified C# EXPRESSION and exit

OPERATION
       Once you launch the csharp command, you will be greeted with the
       interactive prompt:

       $ csharp
       Mono C# Shell, type "help;" for help

       Enter statements below.
       csharp>

       A number of namespaces are pre-defined with C# these include System,
       System.Linq, System.Collections and System.Collections.Generic.  Unlike
       the compiled mode, it is possible to add new using statements as you type
       code, for example:

       csharp> new XmlDocument ();
       <interactive>(1,6): error CS0246: The type or namespace name `XmlDocument' could not be found. Are you missing a using directive or an assembly reference?
       csharp> using System.Xml;
       csharp> new XmlDocument ();
       System.Xml.XmlDocument

       Every time a command is typed, the scope of that command is one of a
       class that derives from the class Mono.CSharp.InteractiveBase.   This
       class defines a number of static properties and methods.   To display a
       list of available commands access the `help' property:
       csharp> help;
       "Static methods:
         LoadPackage (pkg); - Loads the given Package (like -pkg:FILE)
         [...]
         ShowVars ();       - Shows defined local variables.
         ShowUsing ();      - Show active using decltions.
         help;
       "
       csharp>

       When expressions are entered, the C# shell will display the result of
       executing the expression:

       csharp> Math.Sin (Math.PI/4);
       0.707106781186547
       csharp> 1+1;
       2
       csharp> "Hello, world".IndexOf (',');
       5

       The C# shell uses the ToString() method on the returned object to display
       the object, this sometimes can be limiting since objects that do not
       override the ToString() method will get the default behavior from
       System.Object which is merely to display their type name:

       csharp> var a = new XmlDocument ();
       csharp> a;
       System.Xml.Document
       csharp> csharp> a.Name;
       "#document"
       csharp>

       A few datatypes are handled specially by the C# interactive shell like
       arrays, System.Collections.Hashtable, objects that implement
       System.Collections.IEnumerable and IDictionary and are rendered specially
       instead of just using ToString ():

       csharp> var pages = new Hashtable () {
             >  { "Mono",    "http://www.mono-project.com/" },
             >  { "Linux",   "http://kernel.org" } };
       csharp> pages;
       {{ "Mono", "http://www.mono-project.com/" }, { "Linux", "http://kernel.org" }}

       It is possible to use LINQ directly in the C# interactive shell since the
       System.Linq namespace has been imported at startup.   The following
       sample gets a list of all the files that have not been accessed in a week
       from /tmp:

       csharp> using System.IO;
       csharp> var last_week = DateTime.Now - TimeSpan.FromDays (7);
       csharp> var old_files = from f in Directory.GetFiles ("/tmp")
             >   let fi = new FileInfo (f)
             >   where fi.LastAccessTime < LastWeek select f;
       csharp>

       You can of course print the results in a single statement as well:

       csharp> using System.IO;
       csharp> var last_week = DateTime.Now - TimeSpan.FromDays (7);
       csharp> from f in Directory.GetFiles ("/tmp")
             >   let fi = new FileInfo (f)
             >   where fi.LastAccessTime < last_week select f;
       [...]
       csharp>

       LINQ and its functional foundation produce on-demand code for IEnumerable
       return values.  For instance, the return value from a using `from' is an
       IEnumerable that is evaluated on demand.   The automatic rendering of
       IEnumerables on the command line will trigger the IEnumerable pipeline to
       execute at that point instead of having its execution delayed until a
       later point.

       If you want to avoid having the IEnumerable rendered at this point,
       simply assign the value to a variable.

       Unlike compiled C#, the type of a variable can be changed if a new
       declaration is entered, for example:

       csharp> var a = 1;
       csharp> a.GetType ();
       System.Int32
       csharp> var a = "Hello";
       csharp> a.GetType ();
       System.String
       csharp> ShowVars ();
       string a = "Hello"

       In the case that an expression or a statement is not completed in a
       single line, a continuation prompt is displayed, for example:

       csharp> var protocols = new string [] {
             >    "ftp",
             >    "http",
             >    "gopher"
             > };
       csharp> protocols;
       { "ftp", "http", "gopher" }

       Long running computations can be interrupted by using the Control-C
       sequence:

       csharp> var done = false;
       csharp> while (!done) { }
       Interrupted!
       System.Threading.ThreadAbortException: Thread was being aborted
         at Class1.Host (System.Object& $retval) [0x00000]
         at Mono.CSharp.InteractiveShell.ExecuteBlock (Mono.CSharp.Class host, Mono.CSharp.Undo undo) [0x00000]
       csharp>

INTERACTIVE EDITING
       The C# interactive shell contains a line-editor that provides a more
       advanced command line editing functionality than the operating system
       provides.   These are available in the command line version, the GUI
       versions uses the standard Gtk# key bindings.

       The command set is similar to many other applications (cursor keys) and
       incorporates some of the Emacs commands for editing as well as a history
       mechanism too.

       The following keyboard input is supported:

       Home Key, Control-a
              Goes to the beginning of the line.

       End Key, Control-e
              Goes to the end of the line.

       Left Arrow Key, Control-b
              Moves the cursor back one character.

       Right Arrow Key, Control-f
              Moves the cursor forward one character.

       Up Arrow Key, Control-p
              Goes back in the history, replaces the current line with the
              previous line in the history.

       Down Arrow Key, Control-n
              Moves forward in the history, replaces the current line with the
              next line in the history.

       Return Executes the current line if the statement or expression is
              complete, or waits for further input.

       Control-C
              Cancel the current line being edited.  This will kill any
              currently in-progress edits or partial editing and go back to a
              toplevel definition.

       Backspace Key
              Deletes the character before the cursor

       Delete Key, Control-d
              Deletes the character at the current cursor position.

       Control-k
              Erases the contents of the line until the end of the line and
              places the result in the cut and paste buffer.

       Alt-D  Deletes the word starting at the cursor position and appends into
              the cut and paste buffer.    By pressing Alt-d repeatedly,
              multiple words can be appended into the paste buffer.

       Control-Y
              Pastes the content of the kill buffer at the current cursor
              position.

       Control-Q
              This is the quote character.   It allows the user to enter
              control-characters that are otherwise taken by the command editing
              facility.   Press Control-Q followed by the character you want to
              insert, and it will be inserted verbatim into the command line.

       Control-D
              Terminates the program.   This terminates the input for the
              program.

STATIC PROPERTIES AND METHODS
       Since the methods and properties of the base class from where the
       statements and expressions are executed are static, they can be invoked
       directly from the shell.   These are the available properties and
       methods:

       Args   An easy to consume array of any arguments specified after either
              -s or -- on the command line. Ideal for self-executing scripts
              utilizing the -s option.

       void LoadAssembly(string assembly)
              Loads the given assembly.   This is equivalent to passing the
              compiler the -r: flag with the specified string.

       void LoadPackage(string package)
              Imports the package specified.   This is equivalent to invoking
              the compiler with the -pkg: flag with the specified string.

       string Prompt { get; set }
              The prompt used by the shell.  It defaults to the value "csharp>
              ".  string ContinuationPrompt { get; set; } The prompt used by the
              shell when further input is required to complete the expression or
              statement.

       void ShowVars()
              Displays all the variables that have been defined so far and their
              types.    In the csharp shell declaring new variables will shadow
              previous variable declarations, this is different than C# when
              compiled.  void ShowUsing() Displays all the using statements in
              effect.  TimeSpan Time (Action a) Handy routine to time the time
              that some code takes to execute.   The parameter is an Action
              delegate, and the return value is a TimeSpan.  For example:

       csharp> Time (() => { for (int i = 0; i < 5; i++) Console.WriteLine (i);});
       0
       1
       2
       3
       4
       00:00:00.0043230
       csharp>

       The return value is a TimeSpan, that you can store in a variable for
       benchmarking purposes.

GUI METHODS AND PROPERTIES
       In addition to the methods and properties available in the console
       version there are a handful of extra properties available on the GUI
       version.   For example a "PaneContainer" Gtk.Container is exposed that
       you can use to host Gtk# widgets while prototyping or the "MainWindow"
       property that gives you access to the current toplevel window.

STARTUP FILES
       The C# shell will load all the Mono assemblies and C# script files
       located in the ~/.config/csharp directory on Unix.  The assemblies are
       loaded before the source files are loaded.

       C# script files are files that have the extension .cs and they should
       only contain statements and expressions, they can not contain full class
       definitions (at least not as of Mono 2.0).  Full class definitions should
       be compiled into dlls and stored in that directory.

AUTHORS
       The Mono C# Compiler was written by Miguel de Icaza, Ravi Pratap, Martin
       Baulig, Marek Safar and Raja Harinath.  The development was funded by
       Ximian, Novell and Marek Safar.

LICENSE
       The Mono Compiler Suite is released under the terms of the GNU GPL or the
       MIT X11.  Please read the accompanying `COPYING' file for details.
       Alternative licensing for the compiler is available from Novell.

SEE ALSO
       gmcs(1), mcs(1), mdb(1), mono(1), pkg-config(1)

BUGS
       To report bugs in the compiler, you must file them on our bug tracking
       system, at: http://www.mono-project.com/community/bugs/

MAILING LIST
       The Mono Mailing lists are listed at http://www.mono-
       project.com/community/help/mailing-lists/

MORE INFORMATION
       The Mono C# compiler was developed by Novell, Inc (http://www.novell.com,
       http) and is based on the ECMA C# language standard available here:
       http://www.ecma.ch/ecma1/STAND/ecma-334.htm

       The home page for the Mono C# compiler is at http://www.mono-
       project.com/docs/about-mono/languages/csharp/ information about the
       interactive mode for C# is available in http://mono-
       project.com/docs/tools+libraries/tools/repl/



                                  22 March 2017                        csharp(1)