There are components of Linux distributions whose names we all know while others, still widely used, are almost unknown. in this postt tell you what Debian Almquist Shell is qThat is perhaps the best example of my statement.
A shell is a computer program that interprets instructions expressed by words in the form of commands.. When in Linux Adictos We tell you to do something by writing instructions in the terminal, it is a shell that interprets those instructions and puts them into practice.
The Wikipedia article also talks about the existence of a graphical shell (the typical desktop) but most of the references I consulted refer to the use of the command line so we are going to stick with that definition.
How a shell works
The shell is the component of the operating system that works most closely with the user.river. By using a specific programming language you can control processes, manage files, as well as start and control other programs. The shell manages user-computer interaction by first asking the user for input, translating that input so the operating system can understand it, and then dealing with any output resulting from carrying out those instructions. The input can take the form of keyboard input instructions or a script (a series of commands stored in a file.)
At the time of logging into our distribution the system identifies the shell program to run. When we click on the terminal icon, the shell will show us the system symbol identified with the shape of the dollar sign. If we type a command after that prompt and press enter, the shell reads the command and tries to execute it. If it is able to do so, when it finishes it shows the command prompt again or tells us what the error is.
What is Debian Almquist Shell (Dash)
The original UNIX shell was called the Bourne Shell and dates back to 1977. Over time, different forks emerged that kept much of its features, one of them was the Bourne Again Shell (Bash) which, thanks to the GNU project, became an integral part of most Linux distributions.
Well, Debian Almquist Shell fulfills the same functions as Bash in distributions derived from Debian, only it is faster and consumes fewer resources. Although a clarification, It is only used in predefined scripts, when it comes to executing user-created scripts, Bash takes care of it.
It is the Linux port of ash (the Almquist SHell) the NetBSD shell and, although it has been with us since 1997, it only adopted its current name in 2022. The official description of Debian is as follows:
dash is the standard shell for the Linux system. The current version of dash is in the process of being changed to comply with the POSIX 1003.2 and 1003.2a specifications for the shell. This version has many features that make it seem similar in some ways to the Korn shell, but it is not a clone of the Korn shell. Only POSIX-designated functions, plus some Berkeley extensions, are built into this shell.
Korn is another of the Bourne Shell derivatives, while the POSIX specifications are a set of standards that the Institute of Electrical and Electronic Engineers (IEEE) compiled to standardize the way programs interact with the operating system. This facilitates their interoperability.
Then the question arises. If Dash does things faster and using fewer resources Why not use it for everything?
For the same reason you don't use a race car to go grocery shopping.
Dash achieves its economy of resources and takes up less disk space since it uses a single library instead of the multiple dependencies that Bash requires, but That is at the cost of lower benefits. For example, you cannot interact with the user.