Cicada – Unix shell written in Rust

Re:Cicada – Unix shell written in Rust by vidarh on Saturday July 01, 2017 @02:49AM (#14675768)

The problem with modernising the shell stack is that there are a lot of things that depends on the current stack, be it the shell (e.g. see the amount of work it's taken for Ubuntu and Debian to switch to dash as /bin/sh; and dash has a pedigree going back to the 80's), or the upper layers (try to alias "ls" to something that acts differently, and see how many tools depend on parsing its output).

You'd either have to be very careful (e.g. feature flags guarding every change) or expect a surprising amount of things to fail.

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Re:Cicada – Unix shell written in Rust by sirn on Saturday July 01, 2017 @02:58AM (#14675797)

This matches my experience trying to switch the login shell from bash to fish: a surprisingly amount of things failed. macOS users won't have this problem, as the login shell is only started when Terminal/iTerm is started, but in Linux pretty much every process rely on the fact that your $SHELL is POSIX-complaint.

It seems like the way to go to use non-POSIX shell as the default shell without changing login shell, is to have .bashrc `exec`'d that shell when it is running in interactive mode. Regardless, I would really love to see bash-like shell that provides out of the box experience in the same level as fish.

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Re:Cicada – Unix shell written in Rust by gkya on Saturday July 01, 2017 @09:41AM (#14677063)

How come? Having your user's shell sth. non-compliant should not affect other scripts, as they are supposed to specify what interpreter they wanna use via shebang lines; and as long as programs are run with the correct variant of the exec* functions they should be fine.

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Re:Cicada – Unix shell written in Rust by sirn on Saturday July 01, 2017 @10:40AM (#14677287)

I meant the login shell, the one that get executed during console login (i.e. the "-bash" process).

The login shell need to source /etc/profile and /etc/profile.d during logins to populate environment variables. Some apps that expect those environment variable to be present wrote to /etc/profile.d with an expectation that a POSIX-compatible shell and will read the directory (by source-ing those files). The environment variable getting set there ranging from PATH, LANG, to application/distro-specific like MOZ_PLUGIN_PATH.

So when you changed the login shell to something that no longer reads /etc/profile.d (like fish, which actually say it's "interactive shell" in the man page) then application that rely on those variables will start to behave in some funny way, which was the point I was trying to make.

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