Provided by: mono-csharp-shell_5.18.0.240+dfsg-2ubuntu2_all bug

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)