Execute bash command inside fish function

fish

I decided to try fish shell, and I'm having trouble with some aliases. So I guess the painless way of doing the things would be executing the bash commands inside fish shell functions. Something like that :

function fish_function
start bash
    ... bash commands ... 
stop bash
end

Is that possible?

e.g: the command

pacman -Qtdq && sudo pacman -Rns $(pacman -Qtdq)

doesn't work in fish shell and I have no idea how to convert this

Best Answer

Apparently fish uses ; and for && and () for command substitutions.

So just changing the command to

pacman -Qtdq; and sudo pacman -Rns (pacman -Qtdq)

should work.

Answering the actual question, normally you can get a statement to be executed in Bash simply by redirecting the statement to a bash command's STDIN by any mean (notice that I'm on Zsh, which supports here strings, and that the statement prints the content of a Bash-specific variable):

% <<<'echo $BASH' bash
/bin/bash

However as a general rule I'd suggest to use bash's -c option. For example here strings and pipes don't play too well with multiple commands, here documents will be expanded by the current shell, etc (nevertheless those need to be supported by the current shell).

Overall bash -c seems to be always a safe bet:

bash -c 'pacman -Qtdq && sudo pacman -Rns $(pacman -Qtdq)'

Which for multiple commands becomes something like this:

bash -c '
command1
command2
command3
'

Related Solutions

Bash – Converting bash script to fish

Here's some examples of what this would look like in fish:

set -x INBOX $NOTES_HOME/inbox
if [ -d "$MINION_INSTALL" ]
    set -x PATH $MINION_INSTALL $PATH
end

Note the absence of the quotes, which is especially important in the line that sets PATH. Quoting it would collapse all of the paths in the list to a single entry, which is not what you want.

The aliases are valid in fish, except for the $@ at the end. fish has arguments as $argv, not $@, but more importantly, any arguments are implicitly appended to the alias command. So you can just write:

alias newnote="minion --new-note"

Then, for example, newnote foo bar will become minion --new-note foo bar

If you like, you can verify it with functions newnote, which will show you the function that the alias produced.

Hope that helps!

Why doesn’t set -x work within eval within a function in fish

The same thing happens in a simpler form:

function trythis
     set -x foo bar
end

If you now run trythis and echo $foo, it is not set either. That's because fish's -x by itself doesn't change the scope of the variable, which is by default local to the function unless it exists globally or universally already.

Try:

  eval (echo 'set -gx FOO 1;')

Where the g is for global. This makes the variable work like a normal POSIX exported value. It's interesting that it works the same way with eval as it would with just plain set; if you use that line sans g straight on the command line, $FOO is set, so eval and process substitution () have not introduced a new scope or subshell, and when executed that way within a function, the scope of the function applies.

Best Answer

Related Solutions

Bash – Converting bash script to fish

Why doesn’t set -x work within eval within a function in fish

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