Bass makes it easy to use utilities written for Bash in fish shell.

Regular bash scripts can be used in fish shell just as scripts written in any language with proper shebang or explicitly using the interpreter (i.e. using bash script.sh). However, many utilities, such as virtualenv, modify the shell environment and need to be sourced, and therefore cannot be used in fish. Sometimes, counterparts (such as the excellent virtualfish) are created, but that's often not the case.

Bass is created to make it possible to use bash utilities in fish shell without any modification. It works by capturing what environment variables are modified by the utility of interest, and replay the changes in fish.

You might not need Bass for simple use cases. A great simple alternative (suggested by @jorgebucaran) is to just use exec bash -c "source some-bash-setup.sh; exec fish".

Bass is compatible with fish versions 2.6.0 and later.

Use the Makefile.

make install will copy two files to ~/.config/fish/functions/.

make uninstall will remove those two files.

Relaunch the shell for the change to take effect.

omf install bass

fisher install edc/bass

Add

fundle plugin 'edc/bass'

to your fish config, relaunch the shell and run fundle install.

Bass is simple to use. Just prefix your bash utility command with bass:

> bass export X=3
> echo $X
3

Notice that export X=3 is bash syntax. Bass "transported" the new bash environment variable back to fish.

Bass has a debug option so you can see what happened:

> bass -d export X=4
# updating X=3 -> 4
set -g -x X 4

Here is a more realistic example, using the excellent nvm:

> bass source ~/.nvm/nvm.sh --no-use ';' nvm use iojs
Now using io.js v1.1.0

Note that semicolon is quoted to avoid being consumed by fish.

This example takes advantage of the nvm bash utility to switch to iojs. After the command, iojs is accessible:

> which iojs
/Users/edc/.nvm/versions/io.js/v1.1.0/bin/iojs

You can then very easily pack the command as a function and feel more at home:

> funced nvm
nvm> function nvm
           bass source ~/.nvm/nvm.sh --no-use ';' nvm $argv
       end
> nvm list
->  iojs-v1.1.0
         system
> nvm ls-remote
        v0.1.14
        v0.1.15
        
> funcsave nvm
...

(--no-use is an important option to nvm.sh. See #13 for background.)