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Most recent Linux distributions include bash as default shell, although there are other, (arguably) better shells available.

I'm trying to understand if this is some historical leftover that nobody wants to change, or are there some good reasons that make bash the first choice?

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    Most computers are being sold with MS Windows installed, although there are other, arguably better OS's available. Commented Jan 10, 2012 at 10:44
  • Bash is simple. It can usually do everything that user wants it to do. You can easy switch it. That will be not fun to have scsh by default. Commented Jan 10, 2012 at 11:37
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    Bash is OSS implementation of UNIX standard /bin/sh, which is default shell on 'normal' UNIX-es... Commented Jan 10, 2012 at 11:47
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    Please define (arguably) better. I think bash is the best shell because i know it well and it's everywhere, does everything i need concisely and relatively easily, is easily readable, and can be somewhat understood by people without knowing how to create bash scripts. What else do you want from a shell? If you want lots of programming features, you're using a shell incorrectly. Commented Jan 10, 2012 at 13:24
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    Why so many comments? You could've written some of those as answers and still get many upvotes. Commented Jan 10, 2012 at 19:22

6 Answers 6

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The short answer is because linux is really GNU/Linux. Only the kernel is linux but the base collection of utilities providing the Unix like environment is provided by GNU and the GNU shell is bash
As I said, that's the short answer ;)

edited to add some additional commentary...
Let me prefix by saying that I'm not a Unix historian, so I can only answer IMHO

A few points, first of all bash is the kitchen sink of shells, as emacs is to editors.
At the time bash was released there were no free ksh implementations, tcsh was a free csh replacement, but Stallman had a rant against csh for shell programming.
As an interactive shell bash had excellent history/command recall, along with the saving of history from session to session. It was a drop in replacement for sh, bsh, ksh for shell programming and made for a decent interactive shell.
Like a snowball rolling downhill, bash has gained momentum and size.

Yes, there are dozens of other shells; shells that are better suited for individual purpose or taste, but for a single all around shell bash does a decent job and has had a lot of eyes on it for over 20 years.

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    I understand. However, most distributions include many other non-GNU software. It seems to me that bash is used just because it is used, just like choroba commented from Windows being a dominant OS. However, for decades Windows had better hardware support (drivers) which made it hard to switch to other OS. I fail to see what unique feature Bash offers to prevent users from switching? Commented Jan 10, 2012 at 19:21
  • +1 and good one @bdowning for the short and simple answer :-) Commented Jan 11, 2012 at 8:19
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    @MilanBabuškov Bash must be installed because there are too many scripts which use bash-specific features. Once you start from that assumption, you have to justify additional shells. Dash got included in distos like Ubuntu as part of a plan to reduce boot times. Given that bash is "good enough" as an interactive shell, no other shell has yet given a strong enough argument to be part of the default package loadout. Commented Jun 14, 2016 at 12:47
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Bash has some potential competitors:

  • Zsh has more advanced interactive facilities, but a few quirks when it comes to scripting (less so now than back in the days). In the early to mid-1990s when Linux was in its infancy, zsh was virtually unknown.
  • Ksh was the de facto standard on commercial unices since the mid-1980s, but it was proprietary software until 2000, so not an option on Linux. Also, ksh had subpar command line edition capabilities, compared with bash.
  • Pdksh, a free clone of ksh, would have been an option, but it was not well-known and had poor command line edition capabilities. (Pdksh is no longer a very active project, even though it's still used in some BSDs, now that ATT ksh is free.)
  • Some distributions install an ash variant as /bin/sh. Ash (by which I mean any of the loose family of shells called ash) is designed to be small and fast, with no interactive features (it's only for editing scripts). The ash revival is relatively recent; in the 1990s the existing variants lacked a lot of features.
  • Tcsh was the most advanced interactive shell until zsh came along, but it's incompatible with sh and not so good with scripting.

Furthermore bash is the official GNU shell, and Linux systems are really GNU/Linux: many of the core programs come from GNU, even if the best-known part, the Linux kernel, doesn't. At the time it became the de facto standard, bash was well-known, had an official status, and had a decent set of features.

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  • As I understand, the POSIX standard specifies required features for the Bourne shell, at /bin/sh, and most Linux distributions depend upon shell scripts written to use the Bourne shell. BASH is at base an enhanced version of the Bourne shell, and /bin/sh is actually a link to /bin/bash, that when executed runs with just the Bourne shell features. Commented Jan 12, 2012 at 18:18
  • @bgvaughan Some distributions ship bash as /bin/sh, others ship ash. For example Ubuntu's /bin/sh has been dash (the fork of ash maintained by Debian) for a while. Bash has more features, ash is smaller and faster. Both are POSIX compliant (or at least compliant enough in practice). Commented Jan 12, 2012 at 18:54
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Simplest answer? Because something "has to be" the default. The most sensible default is the one that most users are already comfortable with. On that point Bash is a good choice. Everybody has the freedom to choose which is best, in their world. Most will choose to use the default if it has always done what they need.

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    i.e. the Matthew effect Commented Oct 10, 2020 at 7:11
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Coming from DOS (with doskey installed) I really missed the feature to recall the last commands by simply moving the cursor up/down. BASH was IMO the first shell that implemented this on *nix.

So probably most guys from that generation onward liked bash.

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  • While not having used a computer until the 1990s, I was under the assumption that tcsh was the first *nix shell to use the arrow keys to navigate back and forth through the shell history. Commented Jun 17, 2016 at 23:06
  • What kind of argument is that? "I liked the window feature of Windows NT 3.1, so that's I've used it onward" Commented Dec 13, 2021 at 17:59
  • @Nearoo It's a valid kind of argument. Why am I still using a freezer from the 1981? Because it still run fine and does solves all my needs of storing perishable foods. Yes, new models exists with new feature, but i put effort in it and I don't want to put more as long as it suits my needs. Why am I still using bash, because 30 years ago they introduced the feature I needed and made me stop looking around wasting time and effort learning ho to do the same things just because, for me, is enough. Commented Jul 28, 2023 at 14:47
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All the other answers are great, but from a practical standpoint: If I sit down in front of an unfamiliar system (or access it remotely) and I need to do something, I can count on bash being available on all but the oldest systems. I can just go ahead and get things done.

As pointed out in other answers and in your question, there are a lot of other shells (I hear a lot of good things about zsh, but haven't tried it.), but they vary with respect to syntax and sometimes the commands used to get things done. If I just want to get something done, bash is tricky enough without having to adapt to another shell.

Also, when I write a shell script that might be generally useful, I write it for bash and I know that if I'm very careful not to do system dependent things, it will run almost anywhere.

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Inertia.

Bash happened to be the most easily available free shell when Linux (GNU/Linux, if you prefer) systems started appearing. The fact that it's from the GNU project didn't hurt.

As for why it's still the default shell, there's never been a good enough reason to change it. Even if some other shell is better, there are advantages to having the same default login shell across different distributions, and it would be difficult to get everyone (Debian, Red Hat, Suse, etc.) to agree to switch to something else.

And after all, it's only a default. Any user can use chsh to change his or her login shell. There's no need to change the default for everyone.

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