3 ms·

Can you explain why?

Sir_Cmpwn 9y ago
For portability. bash is not available everywhere, but POSIX sh is a requirement of POSIX so you can expect it to be there.
- yjftsjthsd-h 9y ago
  Exactly: GNU bash is on most GNU/Linux systems, but: * mac OS uses an ancient version of bash * Embedded systems use busybox sh * Android uses its own version of sh * None of the BSDs come with bash, since, y'know GNU licensing EDIT: Formatting
  - davewongillies 9y ago
    And to make things interesting Ubuntu uses dash as sh https://wiki.ubuntu.com/DashAsBinSh https://wiki.ubuntu.com/DashAsBinSh
    - OJFord 9y ago
      `sh` is only supposed to be _a_ POSIX-compliant shell, it's not odd/interesting/confusing that Ubuntu uses dash any more than it is that something else uses bash. The shebang line #!/bin/sh should only be used for POSIX-compliant scripts; if it needs {bash, dash, python, etc.} it should start #!/usr/bin/env {bash, dash, python, etc.}.
    - yjftsjthsd-h 9y ago
      In fairness, that's just for sh; if for some reason you actually need bash you can just use `#!/usr/bin/env bash`
      - mjevans 9y ago
        If you actually //need// bash ask for it, not sh. This comes from more armature script authors not being precise enough with requirements, or not targeting the more common and portable spec.
skj 9y ago
Not all systems have bash.
- v_lisivka 9y ago
  Not all systems have POSIX, perl, python, javascript, C++, rust, go, etc., so should we write all our programs and scripts in sh?
  - Goladus 9y ago
    The relevant point is that all systems running bash should also be POSIX compliant. So, taking some care to avoid bash-only constructs in a shell script can reap substantial gains in portability at fairly minor cost.
    - v_lisivka 9y ago
      Why I should care about all systems? If targeted systems have bash4.x and GNU tools, why I should write scripts in sh? If you care about all systems, ANSI C is better choice, IMHO.
      - Goladus 9y ago
        If you're targeting a limited set of systems and can reasonably assume the requirements won't change in the future, obviously use whatever tools you know will be available. I write Bash and Python all the time for those reasons. But it's silly to think that there's nothing in between "complete control over target environment" and "use ANSI C so it can be compiled to any architecture and platform under the Sun." POSIX compliance will cover a lot. Try browsing /usr/bin on any Unix system you'll see plenty of use cases. I just looked at /usr/bin on my laptop and saw that mysqld_safe is a Bourne shell script, for just one example.
wirrbel 9y ago
less magic (which you start to care for if you have to use other people's magic), easier to port stuff to zsh, etc.

For portability. bash is not available everywhere, but POSIX sh is a requirement of POSIX so you can expect it to be there.

yjftsjthsd-h 9y ago
Exactly: GNU bash is on most GNU/Linux systems, but: * mac OS uses an ancient version of bash * Embedded systems use busybox sh * Android uses its own version of sh * None of the BSDs come with bash, since, y'know GNU licensing EDIT: Formatting
- davewongillies 9y ago
  And to make things interesting Ubuntu uses dash as sh https://wiki.ubuntu.com/DashAsBinSh https://wiki.ubuntu.com/DashAsBinSh
  - OJFord 9y ago
    `sh` is only supposed to be _a_ POSIX-compliant shell, it's not odd/interesting/confusing that Ubuntu uses dash any more than it is that something else uses bash. The shebang line #!/bin/sh should only be used for POSIX-compliant scripts; if it needs {bash, dash, python, etc.} it should start #!/usr/bin/env {bash, dash, python, etc.}.
  - yjftsjthsd-h 9y ago
    In fairness, that's just for sh; if for some reason you actually need bash you can just use `#!/usr/bin/env bash`
    - mjevans 9y ago
      If you actually //need// bash ask for it, not sh. This comes from more armature script authors not being precise enough with requirements, or not targeting the more common and portable spec.

skj 9y ago

Not all systems have bash.

v_lisivka 9y ago
Not all systems have POSIX, perl, python, javascript, C++, rust, go, etc., so should we write all our programs and scripts in sh?
- Goladus 9y ago
  The relevant point is that all systems running bash should also be POSIX compliant. So, taking some care to avoid bash-only constructs in a shell script can reap substantial gains in portability at fairly minor cost.
  - v_lisivka 9y ago
    Why I should care about all systems? If targeted systems have bash4.x and GNU tools, why I should write scripts in sh? If you care about all systems, ANSI C is better choice, IMHO.
    - Goladus 9y ago
      If you're targeting a limited set of systems and can reasonably assume the requirements won't change in the future, obviously use whatever tools you know will be available. I write Bash and Python all the time for those reasons. But it's silly to think that there's nothing in between "complete control over target environment" and "use ANSI C so it can be compiled to any architecture and platform under the Sun." POSIX compliance will cover a lot. Try browsing /usr/bin on any Unix system you'll see plenty of use cases. I just looked at /usr/bin on my laptop and saw that mysqld_safe is a Bourne shell script, for just one example.

wirrbel 9y ago

less magic (which you start to care for if you have to use other people's magic), easier to port stuff to zsh, etc.