Scripting

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Marcel's syntax was designed for interactive usage. Instead of extending this syntax to a full-fledged scripting language, marcel provides a Python API, allowing Python to be used as the scripting language. While Python is sometimes considered to already be a scripting language, it isn't really. Executing shell commands from Python code is cumbersome. You've got to use os.system, or subprocess.Popen, and write some additional code to do the integration.

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Marcel provides a Python module, marcel.api, which brings shell commands into Python in a much cleaner way. For example, to list file names and sizes in /home/jao:

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from marcel.api import *

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for file, size in (ls('marcel',

                      'test',

                      file=True,

                      recursive=True) |

                   map(lambda f: (f.path, f.size))):

    print(f'{file}: {size}')

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This code uses the ls and map functions, provided by marcel.api. These correspond to marcel operators that you can use on the command line. Output from ls is a stream of Files, which are piped to map, which maps Files to (file, file size) tuples. ls ... | map ... defines a pipeline (just as on the command line). The Python class representing pipelines defines __iter__, so that the pipeline's output can be iterated over using the standard Python for loop.