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Run executables according to a configuration file

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PyPI version Test Coverage

ciak is a Python program to run executables according to a configuration file (a ciakfile) optionally containing user-declared variables that can be adjusted at runtime.

A ciakfile is a simple text file that describes a nested tree using asterisks and that has placeholders for runtime-controllable variables, supporting defaults. Thanks to the nested tree structure, the amount of typing required is drastically reduced when the same commands have to be executed multiple times but with different arguments. On the other hand, support for placeholders allows for code reuse and the same ciakfile can be used for different situations. This is facilitated by the fact that if you define an environmental variable CIAKFILES_DIR, ciak will know where to look for your ciakfiles, so you can call them from anywhere in your system. Finally, in ciakfiles, every line that does not start with an asterisk (up to leading spaces) is treated as a comment. With this feature, one can write extensive commentaries that perfectly blend in with the configuration itself.

For an example of use case, see the section "Complete explanation of a specific use case". See below for an example of what a configuration file looks like.

Getting started

ciak is available on PyPI. You can install it with pip:

pip3 install ciak

ciak requires python >= 3.9 and has no external runtime dependency. See ciak36 for compatibility with previous versions of Python.

The best way to get started with ciak is to check the examples out.


In this Section, we are going to explore the various ways in which ciak can be used, form the simplest, to the most complex.

Level 0: To run a list of command-line instructions

Suppose you want to execute a set of command-line instructions. For instance, creating a folder, creating three empty files, and moving them inside the folder. (This is a contrived example, but we are going to build upon this later.) A shell script for this task might look like:

mkdir myfolder
touch myfolder/first
touch myfolder/second
touch myfolder/third

This can be easily converted into a ciakfile by prepending asterisks in front of each line:

* mkdir myfolder
* touch first
* touch second
* touch third
* mv first second third myfolder

Now, assuming this is saved into a, it can be executed with

ciak -c

Our contains some redundancies: we run touch three times. With ciak, we can express this more tersely by adding one nesting level

* mkdir myfolder
* touch
** first
** second
** third
* mv first second third myfolder

Saving this into and executing with ciak -c will produce the same result as before. ciakfiles represent sequences of commands using nested trees, so that similar commands can be executed with minimal variation. ciakfiles are meant to be self-documenting: every line that does not start with an asterisk is a comment, so we can expand our example:

* mkdir myfolder
  First, we create our target folder. We will place everything inside here.
* touch
  Next, we create three files (`first`, `second`, `third`).
** first
** second
** third
* mv first second third myfolder
  We move the three files inside our target folder.

Level 1: To parallelize the execution of certain instructions

Building upon our example, ciak supports mixing parallel and serial blocks. For instance, we can demand that the three files first, second, third are created in parallel. To do so, we add * # BEGIN_PARALLEL and * # END_PARALLEL clauses:

* mkdir myfolder
  First, we create our target folder. We will place everything inside here.
* touch
  Next, we create three files (`first`, `second`, `third`).
** first
** second
** third
* mv first second third myfolder
  We move the three files inside our target folder.

Saving this to, and executing with ciak -c, ciak will execute instructions serially, until it finds a parallel block, which is then executed in parallel (with as many cores as available), and then it goes back to running commands serially. The flag --no-parallel transforms parallel blocks into serial ones.

Level 2: To parametrize the execution of certain instructions

ciakfiles are can contain placeholders values that are controlled at runtime. This makes ciak powerful and promotes code reuse. The syntax for command-line adjustable placeholders is {{key::default_value}}.

Consider the simple ciakfile is

* ls {{pwd::/tmp}}

Assuming we save the file to, we can then run

ciak -c --pwd $HOME

This will execute the command ls $HOME. If we were to run

ciak -c

then the default value for pwd is used and the command ls /tmp is run instead.

We can extend our previous example:

* mkdir {{dest::myfolder}}
  First, we create our target folder. We will place everything inside here.
* touch
  Next, we create three files (`first`, `second`, `third`).
** first
** second
** third
* mv first second third myfolder
  We move the three files inside our target folder.

Now, we can control the destination folder when running with through the --dest flag.

Level 3: To write complex workflows once, and use them over and over

We saw that we can produce complex ciakfiles that can be controlled via the command line. The last piece of the puzzle is CIAKFILES_DIR. If you set this environmental variable to a folder, ciak will try to find ciakfiles in that folder (by default it is .). So, with ciak, you can write complex and general workflows and easily invoke them from anywhere in your filesystem. For instance, if you have a ciakfile named compute_result that defined a {{datadir::.}} argument in your CIAKFILES_DIR, you can navigate to the folder where you have the data and execute ciak compute_result. Check the section on ciak and org-mode out to see a real-life example.

The ciakfile configuration syntax

Valid ciakfiles are text files with the following characteristics:

  • Lines that do no start with asterisk (up to initial spaces) are considered comments.
  • The number of asterisks defines the level in the three and the parent of an item is the first item with fewer asterisk above it.
  • Executables have to be on the first level of the tree.
  • Placeholders can be defined with the syntax {{key::default_value}}. These will be substituted at runtime with values specified via command-line or with the default value.
  • Indentation, leading/trailing spaces, and file extension do not matter.
  • Parallel blocks must be at the top level (only one asterisk), they start with # BEGIN_PARALLEL and end with # END_PARALLEL. Nested parallel blocks will be ignored.

Why should I use ciak instead of a shell script?

At a first glance, ciak may seem just a convoluted way to write a shell script. This is not the case: ciak enables workflows that are impractical with shell script. The main advantages of ciak are:

  • Simplify repeated arguments across multiple scripts
  • Easily add keyword arguments with defaults
  • Have parallelization with no effort
  • Strong emphasis on self-documentation

However, by design, ciak does not support any shell feature (like input/output redirection, for loops, variable assignment, ...).

ciak can trivially parallelize the execution of some commands. Hence, you can use it as a replacement of GNU Parallel to parallelize commands defined in a configuration file.


ciak uses features available only with Python3.9 or later versions. For convenience, an executable ciak36 is provided, compatible with Python3.6. There is no difference in features available between ciak and ciak36. ciak36 is automatically generated by ciak with the script. ciak36 will be dropped in the future.

ciak and org-mode

ciak borrows its syntax from GNU Emacs's org-mode . As such, if you save your ciakfiles with extension .org and you open them with Emacs, you gain access to a large number of additional features (e.g., automatic coloring and indentation, subtree folding, tables, exporting to different formats, ...). This is what an example of a ciakfile will look like in (customized) Emacs

org-mode screenshot

Using org-mode greatly enhances ciak's self-documenting capabilities.


--fail-fast, if enabled, ciak stops as soon as a non-zero return code is found.

--no-parellel, if enabled, the commands are executed serially. By defaults, commands are executed in parallel with a number of workers that is equal to the number of available cores on the machine.

--dry-run, if enabled, ciak will print the command that would be executed, without executing any.


We use:

  • Poetry to manage dependencies, build, and publish motionpicture.
  • Black for formatting the code (with 89 columns).
  • pytest for unit tests.
  • coverage for test coverage.
  • mypy for static type analysis.
  • isort to sort the import statements.
  • flake8 for general static analysis.
  • pre-commit to apply linting rules before commits.
  • GitHub actions for continuous integration.

We are happy to accept contributions.

What does ciak mean?

In Italian, the word ciak is an onomatopoeia that indicates the sound of the clapperboard used by movie directors to kick off the recording of a scene. Along the same lines, when you use this program, you are the script-writer and the director: you define what needs to be run in the ciakfile and you start and control its execution with ciak, your clapperboard.

Going over a specific use case

ciak was developed to run analysis of Einstein Toolkit simulations using kuibit. ciak solves four problems:

  1. Simplification in writing the analysis
  2. Reuse of the code
  3. Reproducibility and self-documentation in the analysis
  4. Parallelization of analysis

Normally, one runs several simulations of the same kind with only a handful of parameters changed. The entire analysis can be condensed into a ciakfile which takes as command-line input the folder with the simulation output.

Moreover, distributing the ciakfile along with the scripts that are called allows other people to easily reproduce the analysis. The comments in the ciakfile are helpful to explain what is going on and why certain values are set at the values they are set.

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