shells, bashrc and fish

This post a about some sh/bash/fish configuration and, how to use fish together with bash.

§ the deal with sh

  • the original sh is Bourne-Shell
  • bash stands for Bourne-Shell-Again-Shell, a de-facto replacement to sh.

actually it’s linked to bash (or other shells like dash). Note that when bash and dash etc. are invoked with the sh name, the become more POSIX compliant1.

$ ls -l $(which sh)

lrwxrwxrwx 1 root root /usr/bin/sh -> bash

The there are ports of the original Bourne-Shell (sh) e.g. v7sh

§ the deal with bashrc

– it’s a fuckign mess.

  • login shell: /etc/profile -> ~/.bash_profile -> ~/.bash_login -> ~/.profile
  • interactive non-login shell : /etc/bash.bashrc2 -> ~/.bashrc
  • logout: /bash.bash_logout2 -> ~/.bash_logout
  • non-interactive shell: inherit whatever the calling process has and nothing more.

what is system default doing i.e. /etc/bash.bashrc:

  • check window size per $DISPLAY
  • sets control sequence correctly for the prompt, depending on terminal type (screen, tmux, xterm, foot, …)
  • source completion commands

Note that when using bash as login shell, the ~/.bashrc is not sourced. For it to work, include the following line in ~/.bash_profile or ~/.profile

[[ -f ~/.bashrc ]] && . ~/.bashrc

man bash

When bash is invoked as an interactive login shell, or as a non-interactive
shell with the --login option, it first reads and executes commands from the
file /etc/profile, if that file exists.  After reading that file, it looks for
~/.bash_profile,  ~/.bash_login,  and ~/.profile, in that order, and reads and
executes commands from the first one that exists and is readable.  The
--noprofile option may be used when the shell is started to inhibit this
behavior.

When  an  interactive  login  shell exits, or a non-interactive login shell
executes the exit builtin command, bash reads and executes commands from the
file ~/.bash_logout, if it exists.

When an interactive shell that is not a login shell is started, bash reads and
executes commands from ~/.bashrc, if that file  exists. This may be inhibited by
using the --norc option.  The --rcfile file option will force bash to read and
execute commands from file in‐stead of ~/.bashrc.

refs:

§ fish shell (fuck)

I read on HN that you should set fish as terminal shell instead of login shell (i.e. through chsh). Pretty interesting idea. I’ll try that.

source the source

There are a few issues with fish shell.

  1. it can’t explcitly source .bashrc. Meaning if you are using fish as login shell, it can not use what’s already there. Luckily my plan here is NOT TO use fish as login shell. But I still need a sanity check to make sure .bashrc is already sourced before fish is invoked.
    in .bashrc
    export BASHRC_SOURCED="yes"
    
    in config.fish
    if not set -q BASHRC_SOURCED
        echo "[WARNING!] .bashrc is not sourced, do not use fish as login shell!"
    end
    
  2. bash aliases are not inherited to fish, therefore you need to source it explicitly… (fuck)
    in ~/.bash_aliases
    alias abc=xyz
    # your aliases
    
    in ~/.bashrc
    [[ -f ~/.bash_aliases ]] && . ~/.bash_aliases
    
    in config.fish (perhaps check for file exists, but I won’t bother learning how fish scripting work)
    source ~/.bash_aliases
    

wipe their builtin functions

have you ever wondered why your grep, ls and kill works differently than you expected? Or why your colors are wrong? Or why your aliases doesn’t work? That’s because fish is trying hard to give you wrappers to the very basic stuffs.

  • ls becomes a bloated cyptic script.
  • man becomes a bloated cryptic script.
  • kill receives (__fish_expand_pid_args $argv) which is another layer of cryptic indirection.
  • diff and grep receive --color=auto
  • … check fish_config -> functions for yourself.

Therefore you may want to wipe these builtins. In config.fish

# functions --erase grep
# functions --erase kill
# functions --erase ls
# functions --erase ll
# functions --erase la

Trivias: in case you don’t know, on linux, the commands like cd must be implemented into the shell, not as an external program or script. Every process has a working dir, tracked in task_struct.fs and is changed via the chdir syscall. In otherwords, a process can only change its own workding directory, therefore you can’t implement cd as a program.

§ epilogue

TAKE: While shells are supposed to implement their UNIX builtin functions (like. cd, pushd, popd, jobs … they are not supposed to change how programs work by default. When I call ls I expect to run the program. When I call kill I expect to run the program. I do not want your perks and a expecially do not want your smart-ass coloring.

TAKE: fish sucks, why use it then? – because UNIX eco system sucks more. I’m not hyperthymestic, I can’t remember how those programs are parameterized – and they are not defined in a conventional manner! I fucking need the completion and tooltips, period.


  1. https://wiki.archlinux.org/title/Command-line_shell#POSIX_compliant ↩︎

  2. this depends on the compilation flag.-DSYS_BASHRC or -DSYS_BASH_LOGOUT. This is per-distro. ↩︎ ↩︎


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