local
is undefined.myfunc() {
local i=0
..
}
In POSIX sh, you can adopt some convention to avoid accidentally overwriting variables names, e.g. prefixing with the function name:
myfunc() {
_myfunc_i=0
..
}
local
is supported in many shells, including bash, ksh,
dash, and BusyBox ash. However, strictly speaking, it's not POSIX.
Since quite a lot of real world shells support this feature, you may decide to ignore the warning.
ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.