这些命令似乎表明在导出时不会保留只读bash变量：
Bash 版本 4 或更高版本
f() {
# A local variable will be visible within the function in which it is declared
local a=1
# Declare acts as a synonym (?) to local here, as I do not specify -g (global)
declare b=2
# This is a regular global variable, it won't be in new shells because not exported
declare -g c=3
# You may find this puzzling: _not_ exported because not marked also global
declare -x d=4
# This should be read-only but it does not even get exported
declare -xr e=5
# This will be both global and exported, as expected. Phew :)
declare -gx f=6
# Same as f, global and exported
export g=7
# Now interestingly: this should be exported as read-only, but...
declare -grx h=8
# What does the function scope look like?
printf '%-10s %d%d%d%d%d%d%d%d\n' "local" "$a" "$b" "$c" "$d" "$e" "$f" "$g" "$h"
}
f
# What does the global scope look like?
printf '%-10s %d%d%d%d%d%d%d%d\n' "global" "$a" "$b" "$c" "$d" "$e" "$f" "$g" "$h"
# What does the scope of a new shell look like?
bash -c 'printf "%-10s %d%d%d%d%d%d%d%d\n" "new shell" "$a" "$b" "$c" "$d" "$e" "$f" "$g" "$h"; h=42; echo "$h"'
# Read-only attribute has disappeared after exportation
输出：
local 12345678
global 00300678
new shell 00000678
42
有没有办法导出变量属性？哪些出口好？