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shellfish

How to not expand a command-substitution into multiple parameters

So according to the docs a command written over many lines will expand to multiple parameters. This disagrees with the bash behaviour. For example

hello.lua: 

local msg = "Hello, world!" 
return msg

fish> 

redis-cli EVAL (cat hello.lua) 0

Fails -

Whereas redis-cli EVAL "$(cat hello.lua)" 0 will succeed in bash. My question is how to prevent the (cat hello.lua) substitution from splitting into multiple parameters due to line breaks?

Solution

  • fish does not have a direct analog to bash's "$(...)". The current best technique in fish is to manipulate $IFS, which are the characters that trigger splitting. You can make it empty:

    set -l IFS
redis-cli EVAL (cat hello.lua) 0

    This will pass the entire contents of hello.lua as a single argument.

    Assuming you don't want your IFS changes to stick around, you can scope the change to a function, or to a block:

    begin
  set -l IFS
  redis-cli EVAL (cat hello.lua) 0
end