3 ms·

It is a very kind gesture to make this book freely-available. It does have a small problem in the number of "bashisms" that it quietly promotes. The entire De

by chasil 4y ago

It is a very kind gesture to make this book freely-available. It does have a small problem in the number of "bashisms" that it quietly promotes. The entire Debian/Ubuntu family has chosen the Almquist shell because of speed and standards compliance, and many things in this book will not work there. It would be helpful to have a book that is clear that the POSIX.2 shell is not Bash.

BossingAround 4y ago
> The entire Debian/Ubuntu family has chosen the Almquist shell because of speed and standards compliance, and many things in this book will not work there. So Debian/Ubuntu ship completely without Bash? According to [1], it's Bash, but it might be outdated. [1] https://wiki.debian.org/Bash https://wiki.debian.org/Bash
- chasil 4y ago
  Bash is shipped in Debian/Ubuntu, but as /bin/bash, not as /bin/sh. What is shipped as /bin/sh is described here: http://gondor.apana.org.au/~herbert/dash/ http://gondor.apana.org.au/~herbert/dash/ From the EPEL RPM: "DASH is a POSIX-compliant implementation of /bin/sh that aims to be as small as possible. It does this without sacrificing speed where possible. In fact, it is significantly faster than bash (the GNU Bourne-Again SHell) for most tasks."
  - John23832 4y ago
    Hm but the default shell is still bash. It would make sense that "bashisms" don't work on "sh". You should use bash or bash derivatives (zsh) for bashisms. I think the bigger stumbling block is that people often can't differentiate bashisms from basic shell scripting.
    - gdavisson 4y ago
      bash is the default interactive shell for users, but dash is the default shell for scripts with a #!/bin/sh shebang (or no shebang, unless they're run from bash), system() calls, etc. This means bashisms will work sometimes, which can be worse than not working at all. I agree about the importance of differentiating bashisms from basic scripting, but I think the root cause of that is documentation (including this book) that don't make the distinction.
      - layer8 4y ago
        The book is very clear about the fact that it’s using Bash, even noting when a feature requires a newer version, and uses #!/bin/bash for scripts throughout.
      - John23832 4y ago
        ...But the foreword for any script could just as easily be `#!/bin/bash`... you're choosing not to use bash. If you're on a system with no bash, and are forced to use `sh`, then just don't use bashisms... I'm not trying to be difficult, but I just don't see a problem. Explicitly use bash (or a derivative) if you want bashisms, don't if you do not.
    - quesera 4y ago
      FWIW, zsh is not a bash derivative. Both are spiritual descendants of Bourne shell directly, with some ksh, csh, and tcsh mixed in, in varying proportions.
      - wyclif 4y ago
        Yes, a lot of people don't realise that bash (1989) and zsh (1990) are almost the same age and were parallel projects, not derivative.
      - John23832 4y ago
        True, what I really mean was bash compatibility
John23832 4y ago
Modern Ubuntu/Debian ship with bash? ``` ubuntu@primary:~$ uname -a Linux primary 5.15.0-56-generic #62-Ubuntu SMP Tue Nov 22 19:56:13 UTC 2022 aarch64 aarch64 aarch64 GNU/Linux ubuntu@primary:~$ echo $SHELL /bin/bash ``` dash is the default `/bin/sh` but the default shell is still bash. (man sh gives you dash's man)
- chasil 4y ago
  Bash is the default interactive shell assigned to new users in /etc/passwd. This is different from /bin/sh, which is Almquist.
  - _dain_ 4y ago
    So just put `#!/usr/bin/env bash` at the top of the file
mustache_kimono 4y ago
> It would be helpful to have a book that is clear that the POSIX.2 shell is not Bash. Maybe the one thing I love about Linux culture (compared to the BSDs, illumos, etc.) is that it generally doesn't require everyone to adhere to some high UNIX religion. Writing a shell script of more than 50 lines is hard to do correctly. Bash sometimes makes that a little easier. And it's almost ubiquitous. Forcing new Linux users to learn a POSIX compliant shell, when they are only likely to be using Linux and bash, is simply cruel and unusual. Just as including only `vi` in the base system instead of `nano` is a silly self-own. I see this unreflective question far too often: "Why aren't people using my system and using Linux instead?" And the answer is pretty simple, Linux at least made efforts to reach out to people where they were, in hundreds of low effort ways, whereas your system probably didn't. "Everyone should be using Linux" and/or "should love the command line" is pretty silly, but just as silly is "people should learn the POSIX shell" first. A shell they are likely never to use interactively. Because of a hypothetical portability concern? It's nuts.
- tremon 4y ago
  just as silly is "people should learn the POSIX shell" first Where did the GP make that assertion? I don't see anywhere in the post where they say "please rewrite all the shell examples in POSIX-compliant sh". All I see is a request to inform the reader that not every shell is bash.
- chasil 4y ago
  The origin of this was actually capitalism that bordered on religion. In the UNIX Wars of old, Sun and AT&T attempted to take unreasonable control of System V, which included the Korn shell. DEC, IBM, HP, and others responded with POSIX. https://en.wikipedia.org/wiki/Unix_wars https://en.wikipedia.org/wiki/Unix_wars The impact upon the Korn shall was actually to reduce functionality, and a number of features were removed (arrays, coprocesses, etc.). The reason for this is that the source code for the Korn shell was configured to compile to a 64k text segment (for 286-Xenix), and readability/maintainability was sacrificed. Due to this lineage of the POSIX shell, it is very friendly for embedded systems and other constrained environments in ways that its descendants and competitors are not (and can never be). It deserves to be distinguished from Bash, without question.
deathanatos 4y ago
IMO, the year is 2022, almost 2023. Trying to do POSIX sh is tying both arms behind your back. Set the shebang to #!/bin/bash, and now you've got at least got only one arm tied behind your back. If your environment somehow lacks bash, consider that the bug, and get bash. Or, untie both arms, and use a language that's not going to take every opportunity to stab you in the back with subtle idiocies dating from the last millennium. (But I do agree that, if you're going to put down a bash-ism, it's bash, not POSIX sh.)
- chasil 4y ago
  May I suggest that you attempt to convince The Austin Group/Open Group of your position, to update what was originally known as the POSIX.2 shell standard? https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V... http://www.opengroup.org/austin/faq.html http://www.opengroup.org/austin/faq.html
  - _dain_ 4y ago
    posix is a messy codification of a situation that existed at a particular point in time. it didn't arrive ex nihilo. if enough people decide to just use bash, then that will be the new standard. we don't have to ask for some committee's permission to advance.
    - chasil 4y ago
      Bash as itself, or POSIXLY_CORRECT Bash? It does have something of a split personality on that question.
  - SSLy 4y ago
    The only entity that still respects the Open Group is the sod submitting the SUS/POSIX submissions for macOS on behalf of Apple.
- hsbauauvhabzb 4y ago
  > Or, untie both arms, and use a language that's not going to take every opportunity to stab you in the back with subtle idiocies dating from the last millennium. Are you still referring to bash here?
ghostpepper 4y ago
What's a good alternative book to learn linux command line without bashisms?
- chasil 4y ago
  I really don't know of one. There should be one.
_dain_ 4y ago
what kind of circumstance are people in where they can use posix sh but not bash? in the year 2022? I don't understand it. fucking everything has bash nowadays. and if you're on some machine that unaccountably doesn't have bash, then why can't you just sudo apt install bash, or scp the binary over and chmod +x it? if you can't even do that, maybe reevaluate what life choices got you to this place. life is too short to write strictly posix sh.
- quesera 4y ago
  > posix sh but not bash? Many non-Linuxes, and some Linuxes too. > why can't you just sudo apt install bash Linux is not the whole world. Debian is not the whole Linux. Interactive shells on servers are not guaranteed to be available. Control over the installation image is not guaranteed, or always desirable. > life is too short to write strictly posix sh Alas. Life is too short for writing or responding to uninformed rants. Yet here we both are. POSIX shell scripting has its place. It's not as difficult or complicated as you imagine. The portability tradeoff is valuable or essential in many real-world cases.
  - _dain_ 4y ago
    >Many non-Linuxes, and some Linuxes too. which ones can't run bash? >Linux is not the whole world. Debian is not the whole Linux. Interactive shells on servers are not guaranteed to be available. Control over the installation image is not guaranteed, or always desirable. I didn't literally mean "sudo apt install", I meant "install the thing by whatever means is appropriate to the platform". if you can't install anything then what are you actually doing with it? you have to get your software onto it somehow. and at any rate, the article is literally called "the Linux Command Line" >The portability tradeoff is valuable or essential in many real-world cases. like what? seriously, what? I don't get it. I understand software that has weird/harsh requirements because it's on a super constrained embedded platform. that's a real limitation. but being able to run posix sh but not bash seems like an entirely artificial problem. there's no rigorously conceivable resource constraint that would do that. if your unix is so fucking degenerate that it can't run bash then that's a problem of your own choosing. anyway if it's so easy, you can take on the burden of porting scripts from bash to sh yourself, instead of annoying the rest of us with the "bashisms" whining.
seba_dos1 4y ago
It's not a problem as long as you remember to declare bash as the interpreter instead of relying on sh to be symlinked to bash.

by chasil 4y ago

BossingAround 4y ago

> The entire Debian/Ubuntu family has chosen the Almquist shell because of speed and standards compliance, and many things in this book will not work there. So Debian/Ubuntu ship completely without Bash? According to [1], it's Bash, but it might be outdated. [1] https://wiki.debian.org/Bash https://wiki.debian.org/Bash

chasil 4y ago
Bash is shipped in Debian/Ubuntu, but as /bin/bash, not as /bin/sh. What is shipped as /bin/sh is described here: http://gondor.apana.org.au/~herbert/dash/ http://gondor.apana.org.au/~herbert/dash/ From the EPEL RPM: "DASH is a POSIX-compliant implementation of /bin/sh that aims to be as small as possible. It does this without sacrificing speed where possible. In fact, it is significantly faster than bash (the GNU Bourne-Again SHell) for most tasks."
- John23832 4y ago
  Hm but the default shell is still bash. It would make sense that "bashisms" don't work on "sh". You should use bash or bash derivatives (zsh) for bashisms. I think the bigger stumbling block is that people often can't differentiate bashisms from basic shell scripting.
  - gdavisson 4y ago
    bash is the default interactive shell for users, but dash is the default shell for scripts with a #!/bin/sh shebang (or no shebang, unless they're run from bash), system() calls, etc. This means bashisms will work sometimes, which can be worse than not working at all. I agree about the importance of differentiating bashisms from basic scripting, but I think the root cause of that is documentation (including this book) that don't make the distinction.
    - layer8 4y ago
      The book is very clear about the fact that it’s using Bash, even noting when a feature requires a newer version, and uses #!/bin/bash for scripts throughout.
    - John23832 4y ago
      ...But the foreword for any script could just as easily be `#!/bin/bash`... you're choosing not to use bash. If you're on a system with no bash, and are forced to use `sh`, then just don't use bashisms... I'm not trying to be difficult, but I just don't see a problem. Explicitly use bash (or a derivative) if you want bashisms, don't if you do not.
  - quesera 4y ago
    FWIW, zsh is not a bash derivative. Both are spiritual descendants of Bourne shell directly, with some ksh, csh, and tcsh mixed in, in varying proportions.
    - wyclif 4y ago
      Yes, a lot of people don't realise that bash (1989) and zsh (1990) are almost the same age and were parallel projects, not derivative.
    - John23832 4y ago
      True, what I really mean was bash compatibility

John23832 4y ago

Modern Ubuntu/Debian ship with bash? ``` ubuntu@primary:~$ uname -a Linux primary 5.15.0-56-generic #62-Ubuntu SMP Tue Nov 22 19:56:13 UTC 2022 aarch64 aarch64 aarch64 GNU/Linux ubuntu@primary:~$ echo $SHELL /bin/bash ``` dash is the default `/bin/sh` but the default shell is still bash. (man sh gives you dash's man)

chasil 4y ago
Bash is the default interactive shell assigned to new users in /etc/passwd. This is different from /bin/sh, which is Almquist.
- _dain_ 4y ago
  So just put `#!/usr/bin/env bash` at the top of the file

mustache_kimono 4y ago

> It would be helpful to have a book that is clear that the POSIX.2 shell is not Bash. Maybe the one thing I love about Linux culture (compared to the BSDs, illumos, etc.) is that it generally doesn't require everyone to adhere to some high UNIX religion. Writing a shell script of more than 50 lines is hard to do correctly. Bash sometimes makes that a little easier. And it's almost ubiquitous. Forcing new Linux users to learn a POSIX compliant shell, when they are only likely to be using Linux and bash, is simply cruel and unusual. Just as including only `vi` in the base system instead of `nano` is a silly self-own. I see this unreflective question far too often: "Why aren't people using my system and using Linux instead?" And the answer is pretty simple, Linux at least made efforts to reach out to people where they were, in hundreds of low effort ways, whereas your system probably didn't. "Everyone should be using Linux" and/or "should love the command line" is pretty silly, but just as silly is "people should learn the POSIX shell" first. A shell they are likely never to use interactively. Because of a hypothetical portability concern? It's nuts.

tremon 4y ago
just as silly is "people should learn the POSIX shell" first Where did the GP make that assertion? I don't see anywhere in the post where they say "please rewrite all the shell examples in POSIX-compliant sh". All I see is a request to inform the reader that not every shell is bash.
chasil 4y ago
The origin of this was actually capitalism that bordered on religion. In the UNIX Wars of old, Sun and AT&T attempted to take unreasonable control of System V, which included the Korn shell. DEC, IBM, HP, and others responded with POSIX. https://en.wikipedia.org/wiki/Unix_wars https://en.wikipedia.org/wiki/Unix_wars The impact upon the Korn shall was actually to reduce functionality, and a number of features were removed (arrays, coprocesses, etc.). The reason for this is that the source code for the Korn shell was configured to compile to a 64k text segment (for 286-Xenix), and readability/maintainability was sacrificed. Due to this lineage of the POSIX shell, it is very friendly for embedded systems and other constrained environments in ways that its descendants and competitors are not (and can never be). It deserves to be distinguished from Bash, without question.

deathanatos 4y ago

IMO, the year is 2022, almost 2023. Trying to do POSIX sh is tying both arms behind your back. Set the shebang to #!/bin/bash, and now you've got at least got only one arm tied behind your back. If your environment somehow lacks bash, consider that the bug, and get bash. Or, untie both arms, and use a language that's not going to take every opportunity to stab you in the back with subtle idiocies dating from the last millennium. (But I do agree that, if you're going to put down a bash-ism, it's bash, not POSIX sh.)

chasil 4y ago
May I suggest that you attempt to convince The Austin Group/Open Group of your position, to update what was originally known as the POSIX.2 shell standard? https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V... http://www.opengroup.org/austin/faq.html http://www.opengroup.org/austin/faq.html
- _dain_ 4y ago
  posix is a messy codification of a situation that existed at a particular point in time. it didn't arrive ex nihilo. if enough people decide to just use bash, then that will be the new standard. we don't have to ask for some committee's permission to advance.
  - chasil 4y ago
    Bash as itself, or POSIXLY_CORRECT Bash? It does have something of a split personality on that question.
- SSLy 4y ago
  The only entity that still respects the Open Group is the sod submitting the SUS/POSIX submissions for macOS on behalf of Apple.
hsbauauvhabzb 4y ago
> Or, untie both arms, and use a language that's not going to take every opportunity to stab you in the back with subtle idiocies dating from the last millennium. Are you still referring to bash here?

ghostpepper 4y ago

What's a good alternative book to learn linux command line without bashisms?

chasil 4y ago
I really don't know of one. There should be one.

_dain_ 4y ago

what kind of circumstance are people in where they can use posix sh but not bash? in the year 2022? I don't understand it. fucking everything has bash nowadays. and if you're on some machine that unaccountably doesn't have bash, then why can't you just sudo apt install bash, or scp the binary over and chmod +x it? if you can't even do that, maybe reevaluate what life choices got you to this place. life is too short to write strictly posix sh.

quesera 4y ago
> posix sh but not bash? Many non-Linuxes, and some Linuxes too. > why can't you just sudo apt install bash Linux is not the whole world. Debian is not the whole Linux. Interactive shells on servers are not guaranteed to be available. Control over the installation image is not guaranteed, or always desirable. > life is too short to write strictly posix sh Alas. Life is too short for writing or responding to uninformed rants. Yet here we both are. POSIX shell scripting has its place. It's not as difficult or complicated as you imagine. The portability tradeoff is valuable or essential in many real-world cases.
- _dain_ 4y ago
  >Many non-Linuxes, and some Linuxes too. which ones can't run bash? >Linux is not the whole world. Debian is not the whole Linux. Interactive shells on servers are not guaranteed to be available. Control over the installation image is not guaranteed, or always desirable. I didn't literally mean "sudo apt install", I meant "install the thing by whatever means is appropriate to the platform". if you can't install anything then what are you actually doing with it? you have to get your software onto it somehow. and at any rate, the article is literally called "the Linux Command Line" >The portability tradeoff is valuable or essential in many real-world cases. like what? seriously, what? I don't get it. I understand software that has weird/harsh requirements because it's on a super constrained embedded platform. that's a real limitation. but being able to run posix sh but not bash seems like an entirely artificial problem. there's no rigorously conceivable resource constraint that would do that. if your unix is so fucking degenerate that it can't run bash then that's a problem of your own choosing. anyway if it's so easy, you can take on the burden of porting scripts from bash to sh yourself, instead of annoying the rest of us with the "bashisms" whining.

seba_dos1 4y ago

It's not a problem as long as you remember to declare bash as the interpreter instead of relying on sh to be symlinked to bash.