Turtle is a reimplementation of the Unix command line environment in Haskell so that you can use Haskell as a scripting language or a shell. Think of turtle as coreutils embedded within the Haskell language.

• Install Stack

$ stack ghci turtle
Prelude> :set -XOverloadedStrings
Prelude> import Turtle

... and try out some basic filesystem operations:

Prelude Turtle> cd "/tmp"
Prelude Turtle> mkdir "test"
Prelude Turtle> touch "test/foo"
Prelude Turtle> testfile "test/foo"
True
Prelude Turtle> rm "test/foo"
Prelude Turtle> testfile "test/foo"
False
Prelude Turtle> rmdir "test"
Prelude Turtle> view (lstree "/usr/lib")
FilePath "/usr/lib/gnome-screensaver"
FilePath "/usr/lib/gnome-screensaver/gnome-screensaver-dialog"
FilePath "/usr/lib/libplist.so.1.1.8"
FilePath "/usr/lib/tracker"
FilePath "/usr/lib/tracker/tracker-miner-fs"
FilePath "/usr/lib/tracker/tracker-extract"
FilePath "/usr/lib/tracker/tracker-writeback"
FilePath "/usr/lib/tracker/tracker-search-bar"
FilePath "/usr/lib/tracker/tracker-store"
FilePath "/usr/lib/libgif.so.4.1"
...

To learn more, read the turtle tutorial.

The turtle library focuses on being a "better Bash" by providing a typed and light-weight shell scripting experience embedded within the Haskell language. If you have a large shell script that is difficult to maintain, consider translating it to a "turtle script" (i.e. a Haskell script using the turtle library).

Among typed languages, Haskell possesses a unique combination of features that greatly assist scripting:

• Haskell has global type inference, so all type annotations are optional
• Haskell is functional and not object-oriented, so boilerplate is minimal
• Haskell can be type-checked and interpreted quickly (< 1 second startup time)

• Batteries included: Command an extended suite of predefined utilities

• Interoperability: You can still run external shell commands

• Portability: Works on Windows, OS X, and Linux

• Exception safety: Safely acquire and release resources

• Streaming: Transform or fold command output in constant space

• Patterns: Use typed regular expressions that can parse structured values

• Formatting: Type-safe printf-style text formatting

• Modern: Supports text and system-filepath

turtle's types and idioms are reasonably complete and I don't expect there to be significant changes to the library's core API. The only major functionality that I might add in the future would be to wrap optparse-applicative in a simpler API.

The set of available tools currently covers as many filesystem utilities as I could find across Hackage, but I would like to continue to add to the set of available tools to minimally match coreutils.

• The haskell-turtle tag on Stack Overflow

• Contribute more utilities

• Write turtle tutorials

Copyright (c) 2017 Gabriel Gonzalez All rights reserved.

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