How to make it such that, when running `command`, it automatically does `SOME_ENV_VAR=value command`? (something cleaner than aliases?)

Cyclohexane@lemmy.mlmod to Linux@lemmy.ml – 5 points –

hello friends,

I am looking for a way to do what I described in the title. When running command command, I dont want to have to type SOME_ENV_VAR=value command every time, especially if there are multiple.

I am sure youre immediately thinking aliases. My issue with aliases is that if I do this for several programs, my .bashrc will get large and messy quickly. I would prefer a way to separate those by program or application, rather than put them all in one file.

Is there a clean way to do this?

21

You could source an aliases.sh file on your .bashrc where you define your aliases, so that they don't fill up your bashrc.

For example, in your bashrc:

source ~/.aliases.sh

This way you could also create a file with aliases per program.

FYI: $HOME/.bash_aliases is standard and most distros' .bashrc will source that file by default.

That's a good idea, but it only makes the problem a little better. I still wouldn't want one large aliases.sh file with environment variables for every application I customized. Would rather have them separate somehow without gobbling up a file

You can source other files inside aliases.sh or as @treadful noted .bash_aliases

.bash_aliases:

source .aliases/program_x.sh source .aliases/program_y.sh

This way you can have a file with aliases for each application or group of applications.

But it would be helpful if you provided more information on what you really want to do. Read https://xyproblem.info/

Is there some reason you just don't export those env vars in $HOME/.bashrc or $HOME/.bash_profile?

export SOME_ENV_VAR=value

If it's every time you run the command, seems like it should be set globally.

Because it's not as maintainable as separating them by application or some other separation. Would not want to fill up my bashrc with single-application specific code.

You could break it out into other files if you really got that much going on. But if you really have hundreds or more env vars, maybe you should re-think using env vars at all.

Hard to give a rec without more detail, so I don't really get it.

Put your aliases in .bash_aliases

Make sure your .bashrc sources .bash_aliases like this:

if [ -f ~/.bash_aliases ]; then . ~/.bash_aliases fi

You can add a new executable in your ~/.local/bin directory like command_custom that would start SOME_ENV_VAR=value command. Like if you use bash:

#!/usr/bin/bash

SOME_ENV_VAR=value command

Do not forget to chmod +x the file to make it executable.

This way you will have additional command for your user only (no sudo require to create/update those), for system-wise command put it in /usr/local/bin.

You could alias the your programs' commands to invoke the environment variables.

Or, use an alias to source an environment file before launching the binary?

If you were using Zsh, one way you could do this is by autoloading function files from a folder in your fpath.

Let's say you're using ~/.local/share/zsh/site-functions for your custom functions. To ensure that folder is an early part of your fpath, put something like this within your .zshrc:

typeset -U fpath=(~/.local/share/zsh/site-functions $fpath)

Then let's say you want to override the uptime command. Add a file ~/.local/share/zsh/site-functions/uptime with content like:

NO_COLOR=1 =uptime

::: spoiler Explanation for the second =:

 `=' expansion
     If  a word begins with an unquoted `=' and the EQUALS option is set, the remainder of the word is taken as the name of a command.  If a command ex‐
     ists by that name, the word is replaced by the full pathname of the command.

:::

The last thing you need to do is mark it for autoloading, in your .zshrc:

autoload -Uz uptime

Instead of listing those functions manually as arguments, you could instead use a glob pattern to collect all those names, excluding any which begin with _ (completion functions):

autoload -Uz ~/.local/share/zsh/site-functions/[^_]*(:t)

function command_one() {
    # activate the environment
    source "$XDG_DATA_HOME/venvs/alpha.sh"
    # run the thing
    actual_command_one
}

function command_two() {
    # activate the environment
    source "$XDG_DATA_HOME/venvs/alpha.sh"
    source "$XDG_DATA_HOME/venvs/bravo.sh"
    # run the other thing
    actual_command_two
}

You could write a shell script:

#!/usr/bin/env sh

export SOME_ENV_VAR=value

command

Then place it on your path, for example /usr/local/bin/command_with_env.

I avoided overriding the command itself and naming the script the same, because then I think it would try to invoke itself.

Just replace command in your script with /usr/bin/command or whatever. It’s generally good practice to full path anything run from a script anyway just to remove any unintended environment dependencies.

Good point. But then if both the script and the command have the same filename, it will be important to make sure the script has a higher precedence in the PATH. Adding it to the end of .bashrc should be enough I think.