Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. It only takes a minute to sign up.
Sign up to join this community
I found references for parameter expansion, but none of them explain what $^@ does. From context, I think it's used to expand e.g. ~/$^@ into ~/$1 ~/$2 ..., but I'm not sure, and I can't find any confirmation. In addition to an explanation, I'd appreciate knowing what this expansion is called, and a link to documentation about it if possible. Thanks!
EDIT: I've been informed this might be particular to zsh. If anyone has further information, please let me know.
In the zsh shell, foo${^array}bar, where array is an array, like (a b c), would expand to fooabar, foobbar, and foocbar (like a brace expansion would expand) instead of to the strings fooa, b, and cbar:
$ array=(a b c)
$ print -rC1 foo${^array}bar
fooabar
foobbar
foocbar
$ print -rC1 foo${array}bar
fooa
b
cbar
In the code that you quote, this is used to append ~/ (the pathname of the user's home directory) to each element of the list of positional parameters:
$ set -- a b c "bumble bee"
$ print -rC1 ~/$^@
/home/myself/a
/home/myself/b
/home/myself/c
/home/myself/bumble bee
~/$^@ is the same as ~/${^@}. $@ or ${@} is the list of positional parameters (commonly the arguments given to the current script or shell function, or the strings set with the set built-in utility, as shown above).
Search the zshall manual for RC_EXPAND_PARAM. The expansion may originally come from the rc shell.
rc does by default, and see the ^ operator there as well. But the behaviour is different when joining two arrays. Compare rc -c 'a=(a b); echo $a^X' with zsh -c 'a=(a b); echo ${^a}X' and rc -c 'a=(a b); echo $a^$a' vs zsh -c 'a=(a b); echo $^a$^a'. The behaviour of zsh -o rcexpandparam is more like the default behaviour of fish (fish -c 'set a a b; echo $a$a')
Nov 19, 2021 at 17:13
zshscript? That shell would be able to do exactly that, and it means exactly what you have described, it appends a string to all elements of an array. I'm not turning this into a proper answer as I don't know for sure what shell the script was written for (there may be other shells that does something similar, Stéphane would know).echo ~/$^@zshthenecho ~/$^@doesn't do anything.