Display ZSH brace expansion

zsh

Is there a way to show the expanded version of a brace expansion statement?

For example, I have:

$ bundle exec rake db:{drop,create,migrate}

Does the expanded version expand to this?

$ bundle exec rake db:drop
$ bundle exec rake db:create
$ bundle exec rake db:migrate

Best Answer

Well, you could always just do

~  for i (drop create migrate) echo bundle exec rake db:$i
bundle exec rake db:drop
bundle exec rake db:create
bundle exec rake db:migrate

~ echo bundle exec rake db:{drop,create,migrate}
bundle exec rake db:drop db:create db:migrate

Related Solutions

Bash – How to suppress the space between generated arguments during brace expansion

You could store the brace expansion in an array, then output it in the manner of your choosing:

urls=( localhost:8080/reports/{promos,promo-updates,scandown}/{130,139,142}{,-unburdened,-burdened}{,.pdf,.xls,.xlsx,.csv,.preload} )

Then

printf "%s\n" "${urls[@]}"

(IFS=$'\n'; echo "${urls[*]}")

The echo example looks weird because:

it's run in a subshell (the parentheses) so I don't alter my current value of IFS.
IFS needs to be defined in a separate command:
- This doesn't work: IFS=$'\n' echo "${urls[*]}" because the variable gets expanded before the new env variable takes effect
- IFS needs to be set before you start expanding variables.

Also, note the subtle difference in the dereferencing array index used:

[@] in the printf example to expand the array into individual words
[*] in the echo example to expand the array into a single word, with elements separated by the first char of IFS

Zsh Tilde – How Tilde Expansion Works

~ is expanded only in a few contexts. POSIX, for the standard sh mandates echo a=~ to output a=~ (while it mandates ~ to be expanded in a=~ alone).

zsh however has a magicequalsubst option which you can use for ~ to be expanded after = even if it's not in assigments or arguments to the export/typeset... pseudo-keywords.

So:

$ echo a=~
a=~
$ set -o magicequalsubst
$ echo a=~
a=/home/chazelas

Note that bash, when not in POSIX/sh mode, expands ~ in word=~ but only when what's on the left of = looks like a literal unquoted bash variable name (regardless of whether it's in arguments to typeset/declare/export or any other command):

$ bash -c 'echo a=~'
a=/home/chazelas
$ bash -c 'echo "a"=~'
a=~
$ bash -c 'var=a; echo $var=~'
a=~
$ bash -c 'echo a.b=~'
a.b=~
$ (exec -a sh bash -c 'echo a=~')
a=~

Best Answer

Related Solutions

Bash – How to suppress the space between generated arguments during brace expansion

Zsh Tilde – How Tilde Expansion Works

Related Question