Shells: How To Use A Modified Environment In Commands

Introduction

I love fish 🐟 shell because of its convenient auto suggestions and excellent performance.

I had, however, a slightly serious problem on switching from bash.
I didn't know how to use a modified environment in commands.

For example, I was in search for how to change the names of home subdirectories, and found the bash solution like this 🤔:

LANG=C xdg-user-dirs-gtk-update

This means running the xdg-user-dirs-gtk-update command with setting "C" for the LANG environment.
Running the same command failed in fish shell...🥴

I, however, didn't feel like always using an additional step such as the bash command or set.

I wrote this post so as to demonstrate how to solve it.

* Besides: Just today, I found fish prints the great error message. Holy mackerel! :

fish: Unsupported use of '='. To run 'xdg-user-dirs-gtk-update' with a modified environment, please use 'env LANG=C xdg-user-dirs-gtk-update…'

Body

In order to set a modified environment, it's possible in bash by using the SOME_ENV=value format at the top:

EDITOR=vi git commit

It's also the same about ksh / zsh.

But not about fish!

There isn't any solution? Yes. It's possible if we use env command 😊:

SOME_VAR=1 command produces an error: Unknown command "SOME_VAR=1".
Use the env command.
env SOME_VAR=1 command
You can also declare a local variable in a block:

The env SOME_ENV=value format works nicely!!

env SOME_ENV=vi git commit

It's the same about tcsh.

Conclusion

References And My Thanks To

• https://fishshell.com/docs/current/faq.html#faq-single-env
• http://hyperpolyglot.org/unix-shells

Happy operating 🐈