How to set an alias on a per-directory basis?

Question

Suppose you have an alias go, but want it to do different things in different directories?

In one directory it should run cmd1, but in another directory it should run cmd2

By the way, I have an aliases for switching to the above directories already, so is it possible to append the go alias assignment to the foo alias?

alias "foo=cd /path/to/foo"

Working in bash(?) on OSX.

Answer 1

It is not completely sure what you are asking, but an alias just expands to what is in the alias. If you have two aliases, you can append the different commands, even aliases.

alias "foo=cd /path/to/foo; go"
alias "foo2=cd /path/to/foo2; go"

In any other situation, you could specify a function in your .bashrc

function go ()
{
    if [ "$PWD" == "/path/to/foo" ]; then
       cmd1
    elif [ "$PWD" == "/path/to/go" ]; then
       cmd2
    fi;
}

In case you have more choices, you could better use a case structure.

Answer 2

If you add the following function to your .bashrc

function cd () { 
  builtin cd "$@" && [[ -f .aliases ]] && . .aliases
  return 0
}

Every time you cd to a directory with an .aliases file it will get sourced.

Careful with security if others can create files on your machine.

With this trick aliases never get removed but you can write as much code as you like in the function.

ondir uses this trick and has a ton of bells and whistles.

http://swapoff.org/ondir.html#download

Answer 3

I get the feeling you are very "directory oriented", and, in that case, this might suite your mentality better.

(But to be honest, I think this is a bad idea altogether, you'd like commands to be global.)

In .bashrc, put alias go="./.cmd" (then source ~/.bashrc).

Then, in each such directory, put a script called .cmd, then chmod +x .cmd, then just go do your thing.

Answer 4

I'm working on a project that accomplishes just that. Check it out: localalias.

Here's a demo:

Funny enough, I actually used go as an example in the demo. I did not show switching directories (something I should change about the demo) but the functions with the la command are indeed local to the directory they are defined in.

Answer 5

I was searching for a way to do this for quite a while, and today I came up with a solution that is a synthesis of some of the other answers, but with a secret ingredient that spikes the sauce; direnv.

The problem with having .aliases that is read every time, as proposed by @teknopaul, is as mentioned, that you accumulate definitions and they never unload. direnv solves this issue by loading and unloading environment variables on a per-directory basis. Still, this just handles environment variables, but we can use this together with functions!

So here is my alias for npm (which, of course, is not an alias, but a function):

function npm(){ if [[ -z "$NPMBIN" ]]; then $(which npm) $@; else $NPMBIN $@; fi; }

You can also rewrite the above to a true alias, by executing the logic in a sub-shell, but then you need to mind your escaped quotes!

alias npm='bash -c "if [[ -z \"$NPMBIN\" ]]; then $(which npm) $@; else \"$NPMBIN\" $@; fi;"'

Answer 6

function go() {
  if [ ! -e "./.cmd1" ]
    then command go -a $1
    else command go -b $1
  fi
}

Similar thing, but assuming "go" is a command you want different functionality from in a specific directory.

Answer 7

i realized this via direnv and a shell script what is called via an alias

~/folder_a/.envrc

export GO_TO_DIR="./subdir_a"

~/folder_b/.envrc

export GO_TO_DIR="~/another_dir"

my go_to.sh

#!/bin/sh
value="${GO_TO_DIR}"

if [ -z $value ]
then
  exit 0
fi

cd $value

don't forget to make this file executeable

chmod u+x /path/to/script/go_to.sh

now i've set an alias to this script in my ~/.bashrc and ~/.zshrc and it works

alias goto="sh /path/to/script/go_to.sh"

bonus:

1. i can sat a global env to change to a standard destination until it is overwritten with the directory specific env

2. if no env is defined, nothing will happen

__

a second way without a script is to change the alias directly test if the env exists

alias goto='sh -c "if [ ! -z ${GO_TO_DIR} ]; then cd ${GO_TO_DIR}; fi;"'

Answer 8

Building upon @teknopaul his answer, I added a little hack that ensures the previous aliases get tossed by replacing the current shell with a new bash instance using exec:

cd () {
  builtin cd "$@" && exec bash
}

if [ -f $PWD/.aliases ]; then
    . $PWD/.aliases
fi

Note that this will break chaining cd with consecutive command executions