2y ago

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

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 comments

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

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.

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.
  
  Most Debian based distros, actually.
- 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/

You could write a shell script:
sh

#!/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.

 undefined

    
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
}

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:
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?

Is this a use case where you can use dotenv? (folder specific environment variables?)
If it's not, aliases are the best you can do, or bash functions that are equivalent to them. The thing is that those only run in bash, so if you are expecting to run the commands outside of a shell, you will need to wrap them in bash -c or have a wrapper script.
This is just the broad strokes so if you have any questions please follow up.

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:
undefined

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:
undefined

NO_COLOR=1 =uptime

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

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):
undefined

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

21 comments