Marcel – modern shell

Marcel is a modern shell that uses Python values rather than plain text as the primary data passed through pipelines.

Streams can contain strings and numbers as well as lists, tuples and objects representing files, processes, history records and workspaces.

This object-oriented pipeline model allows data to be filtered, transformed and formatted using ordinary Python expressions instead of specialised languages such as those embedded in awk and find. Marcel operators can be mixed with conventional Unix executables, with strings used automatically at the boundary between the two models. Python also serves as the full scripting language through the marcel.api module.

This is free and open source software.

Key Features

• Pipelines pass structured Python values between Marcel operators.
• Streams can contain strings, numbers, lists, tuples and arbitrary Python values.
• Dedicated objects represent files, processes, history entries and workspaces.
• Filter pipeline data using Python expressions and functions.
• Transform values using the map operator.
• Sort, reverse, select, join and deduplicate streamed data.
• Set operations include union, intersection and difference.
• Built-in ls operator produces File objects rather than formatted text.
• Process listings are represented as Process objects.
• Mix Marcel operators and ordinary operating-system executables in one pipeline.
• Automatically converts to string streams when communicating with external commands.
• Assign pipelines to variables to create reusable operators.
• Reusable pipelines can accept positional and named parameters.
• Store pipeline results in environment variables and recall them later.
• Environment variables can contain structured and mutable Python values.
• Evaluate Python expressions directly from the command line.
• Import Python modules and symbols into the Marcel namespace.
• Python API brings Marcel operators and pipelines into ordinary Python programs.
• Pipeline output implements Python iteration for use in for loops.
• Run simple Marcel command files or build more sophisticated scripts in Python.
• Built-in operators for files, processes, SQL, streams and environment management.
• Directory stack with cd, pushd, popd, dirs and pwd operators.
• Foreground and background job management.
• Run Marcel pipelines with elevated privileges through the sudo operator.
• Execute a pipeline across every host in a configured remote cluster.
• Remote output is labelled with the originating host.
• Named workspaces maintain separate environments, histories and startup scripts.
• Create, list, open, close and delete workspaces.
• Command history with editing, replay and reverse search.
• Tab completion for operators, flags and filenames.
• Integrated help covering concepts, objects and individual operators.
• Customisable prompts and colour schemes.
• Changes to startup and configuration files are applied without restarting the shell.

Website: github.com/geophile/marcel
Support:
Developer: Jack Orenstein
License: GNU General Public License v3.0

Marcel is written in Python. Learn Python with our recommended free books and free tutorials.

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