The Almquist shell (ash) has spawned numerous variants over the years, each with its own focus and features. These range from minimal, resource-constrained versions like BusyBox ash, suitable for embedded systems, to enhanced shells like ksh, dash, and zsh that prioritize performance, portability, or extended functionality. The post provides a comprehensive list of these ash derivatives, briefly describing their key characteristics and intended use cases, along with links to their respective projects. This serves as a valuable resource for understanding the ash lineage and selecting the appropriate shell for a given environment.
This webpage, titled "Ash (Almquist Shell) Variants," provides a comprehensive overview of various forks, derivatives, and implementations of the Almquist Shell (ash), a lightweight and portable Unix shell known for its speed and small footprint. The author meticulously catalogs a diverse range of ash-based shells, emphasizing their individual characteristics and historical context.
The core of the document is a structured list, categorizing the different ash variants. This categorization includes "Direct ash derivatives," comprising shells like the original ash itself, maintained by Kenneth Almquist, as well as prominent forks such as BusyBox ash, the default shell in many embedded systems. Another category, "Shells based on ash," encompasses projects like dash (Debian Almquist shell), which serves as the /bin/sh in Debian and Ubuntu systems, and other shells that borrowed heavily from ash's design but have since diverged significantly. Furthermore, the document identifies "Shells inspired by ash," acknowledging shells that share philosophical similarities or design principles with ash, even if their codebases are not directly related. Finally, there's a category for "Discontinued projects," documenting shells that were once based on or inspired by ash but are no longer actively maintained.
For each listed shell, the webpage offers a concise description, outlining its key features, target platforms, and its relationship to the original ash. It often includes links to the project's homepage, source code repository, or related documentation, facilitating further exploration for interested readers. The document also highlights the historical lineage of these shells, tracing their evolution and branching from one another, showcasing the influence of ash on the broader landscape of Unix shells. This detailed record provides valuable insights into the development and proliferation of ash-based shells within various operating systems and embedded environments, illustrating their importance in the Unix ecosystem.
The meticulous organization and extensive information provided on this page make it a valuable resource for anyone interested in understanding the history, diversity, and ongoing development of shells derived from the Almquist Shell. It serves as a central repository of knowledge for researchers, developers, and users alike who seek to navigate the complex world of ash and its numerous descendants.
Summary of Comments ( 2 )
https://news.ycombinator.com/item?id=43943984
HN users discuss various Ash-derived shells, primarily focusing on their size and suitability for embedded systems. Some highlight BusyBox's ash implementation as a popular choice due to its configurability, allowing developers to tailor its feature set and size. Others mention alternative shells like dash, praising its speed and adherence to POSIX standards, while acknowledging it lacks some features found in Bash. Several users express interest in smaller, more specialized shells, including ksh and hush, and discuss the trade-offs between size, features, and compliance. The thread also touches upon licensing considerations, static linking, and the practicality of using different shells for various tasks within a system.
The Hacker News post "Ash (Almquist Shell) Variants" sparked a discussion thread with several insightful comments. The conversation primarily revolves around the different ash-derived shells, their performance characteristics, and suitability for various use cases.
One commenter highlights the popularity of
dashas the/bin/shon Debian and its derivatives, emphasizing its role as a POSIX-compliant shell optimized for speed and small size. They further elaborate on the distinction betweendashas a system shell and interactive shells likebashandzsh, which offer richer features for interactive use but come with a performance overhead. This distinction reinforces the rationale behind using a leaner shell likedashfor system scripts where speed and resource efficiency are critical.Another comment delves into the history of
ashand its evolution, mentioning Kenneth Almquist's original creation and its subsequent adoption and modification in various projects like BSD and Debian. They explain thatdashis essentially a maintained version of NetBSD'sash, indicating a lineage that ensures ongoing development and bug fixes. This historical context provides a deeper understanding of the relationships between the different ash variants.Further discussion touches upon the resource consumption of shells, with one commenter observing that
dashconsumes considerably less memory compared tobash. This observation reinforces the argument for usingdashin resource-constrained environments or for scripts where minimizing overhead is paramount.The practical implications of shell choice are also discussed, with a comment suggesting that using
dashcan significantly speed up boot times and improve overall system responsiveness. This comment is particularly relevant for users seeking to optimize their system's performance.A comment also explores the licensing aspects of different shells, mentioning the switch from the original Almquist Shell license to a BSD license. This provides relevant information for developers concerned about licensing compatibility.
The discussion also touches upon the trade-offs between functionality and performance, acknowledging that while
bashoffers a wider range of features,dashexcels in speed and efficiency. This highlights the importance of choosing the right shell based on the specific requirements of the task at hand.Finally, a commenter shares personal experiences with
dash, highlighting its value in situations where strict POSIX compliance is necessary. This anecdote further emphasizes the practical benefits of usingdashin certain contexts.Overall, the comments provide valuable insights into the history, features, and trade-offs of the various ash-derived shells, offering practical advice for choosing the right tool for different use cases.