---
name: "mcstas"
section: "1"
platform: "linux"
package: "mcstas"
version: "3.5+3.5.19+ds5-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/mcstas"
---

# mcstas(1)

## NAME

**mcstas** Compiler of the mcstas neutron ray-trace simulation package

## SYNOPSIS

**mcstas** \[-o file\] \[-I dir1 ...\] \[-t\] \[-p\] \[-v\] \[–no-main\] \[–no-runtime\] \[–verbose\] file

## DESCRIPTION

The compiler for the mcstas instrument definition is invoked by typing a command of the form `mcstas name.instr` in a shell or command prompt. This will read the beamline definition `name.instr` which is written in the mcstas meta-language. The compiler will translate the instrument definition into a Monte Carlo simulation program provided in ISO-C. The output is by default written to a file in the current directory with the same name as the instrument file, but with extension `.c` rather than `.instr`. This can be overridden using the `-o` option as follows: `mcstas -o code.c name.instr` which gives the output in the file `code.c`. A single dash `-` may be used for both input and output filename to represent standard input and standard output, respectively. The default component search list is usually defined by the environment variable `MCSTAS` (default is `/usr/share/mcstas/resources`).

Often, it will be more convenient to use the front-end program `mcgui` or `mcrun`. These front-ends will compile and run the simulations automatically.

The usual instrument syntax is:

-

  ```
  DEFINE INSTRUMENT name(parameters)
  DECLARE %{
    // C_code
  %}
  INITIALIZE %{
    // C_code
  %}
  TRACE
  COMPONENT name = comp(parameters)
  WHEN (condition)
  AT (...) [RELATIVE reference
  {ROTATED {RELATIVE reference }
  EXTEND %{
    // C_code
  %}
  FINALLY %{
    // C_code
  %}
  END
  ```

## OPTIONS

- **-o FILE –output-file=FILE**

  Place C output in file FILE.

- **-I DIR –search-dir=DIR**

  Append DIR to the component search list.

- **-t –trace**

  Enable \`trace' mode for instrument display.

- **-v –version**

  Prints mcstas version.

- **–no-main**

  Do not create main(), for external embedding.

- **–no-runtime**

  Do not embed run-time libraries.

- **–verbose**

  Display compilation process steps.

- **–source**

  Embed the instrument source code in executable.

## FILES

/usr/share/mcstas/resources /usr/share/mcstas/tools/Python/mccodelib/mccode\_config.json ~/.mcstas/mccode\_config.json http://www.mcstas.org

## EXAMPLES

- Translate the *Test\_SX* example (Single crystal diffraction) into C

  - •

  `mcstas Test_SX.instr`

- •

  `gcc Test_SX.instr -o Test_SX.out -lm`

## AUTHORS

mcstas Team (mcstas.org)

## SEE ALSO

[mcstas(1)](/mcstas/1.md), [mcdoc(1)](/mcdoc/1.md), [mcplot(1)](/mcplot/1.md), [mcrun(1)](/mcrun/1.md), [mcgui(1)](/mcgui/1.md), [mcdisplay(1)](/mcdisplay/1.md)

## AUTHORS

MCSTAS neutron Ray Tracing Team.