"withenv" runs a shell command in the context of a named environment.
For example:
$ withenv my-aws-credentials -- aws s3 list-buckets
Here, "my-aws-credentials" is the name of the environment, and "aws s3 list-buckets" is the command to run.
"withenv" is implemented using bash shell functions. Install it with:
source path/to/withenv/withenv.bash
In this context, an "environment" means a set of environment variables. You define environments by creating shell-script fragments which set environment variables, e.g.
# /Users/mdub/.withenv/my-aws-credentials
export AWS_ACCESS_KEY_ID=AKIBIJQ4XSWNFIF426NQ
export AWS_SECRET_ACCESS_KEY=abNFIEVdwcQdeadbeefnnShq4B1pG7qZ9sqNwoFO
They're just shell scripts; withenv will "source" them as required.
You can specify a full path to the environment file:
$ withenv /etc/aws-credentials.sh -- aws ec2 list-instances
Or, you can just supply a short-name (as in the first example), in which case we'll look for the file in $WITHENV_DIR (which defaults to $HOME/.withenv).
If multiple environments are specifed, withenv will load them all:
$ withenv my-aws-credentials ruby-gc -- funky-aws-stuff.rb
withenv comes complete with Bash programmable completion support, for no extra cost. For example:
$ withenv my-aw[TAB]
$ withenv my-aws-credentials