csharp(1) General Commands Manual csharp(1)
NAME
csharp - Interactive C# Shell and Scripting
SYNOPSIS
csharp [--attach PID] [-e EXPRESSION] [file1 [file2]] [compiler-op-
tions] [--|-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 inter-
preter 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 ar-
guments 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 uti-
lize 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 avail-
ble 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 inter-
active 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 dis-
play 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 Sys-
tem.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 IEnumer-
able return values. For instance, the return value from a using `from'
is an IEnumerable that is evaluated on demand. The automatic render-
ing of IEnumerables on the command line will trigger the IEnumerable
pipeline to execute at that point instead of having its execution de-
layed 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 dec-
laration 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 se-
quence:
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 his-
tory 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 com-
plete, or waits for further input.
Control-C
Cancel the current line being edited. This will kill any cur-
rently 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 po-
sition.
Control-Q
This is the quote character. It allows the user to enter con-
trol-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 pro-
gram.
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 meth-
ods:
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 expres-
sion 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 state-
ments 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 exam-
ple:
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 ver-
sion there are a handful of extra properties available on the GUI ver-
sion. 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 lo-
cated 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 defini-
tions should be compiled into dlls and stored in that directory.
AUTHORS
The Mono C# Compiler was written by Miguel de Icaza, Ravi Pratap, Mar-
tin 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/commu-
nity/help/mailing-lists/
MORE INFORMATION
The Mono C# compiler was developed by Novell, Inc (http://www.nov-
ell.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 in-
teractive mode for C# is available in http://mono-
project.com/docs/tools+libraries/tools/repl/
22 March 2017 csharp(1)
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