Bash variable scope

Bash has two types of scopes: Global scopes, namely the declared variables by default, and local scopes.

1) global variable declaration involves the following situations:

#!/bin/bashmm=12 #visible globallyfunc() {    mn=34  #visible globally    echo "mc=${mc}" #is visible}mc=35  #visible globally# echo "mn={$mn}"  #is not visiblefuncecho "mm=${mm};mn=${mn};mc=${mc}"

However, the global variable Mn declared in the function is invisible before the main function is called.

2) local scope: When declaring a variable, add the local keyword before and apply it only to the function. Its scope
Only visible in the current function block and Its subfunctions.

#!/bin/bashfunc1() {    local loc1=11    echo "func1 loc1=${loc1}" #is visible}func2() {    echo "func2 loc1=${loc1}"  #is visible}func1echo "local loc1:${loc1}" #not visible

There is a special case: when the Declaration of local variables and the setting is in a single command line, the operation order is displayed, the variable is set first,
Then, limit the scope of the variable. This result is reflected in the return value.
As follows:

#!/bin/basht=$(exit 1)echo $?  #  return 1echo "t=${t}"func() {    t1=$(exit 1)    echo $?     #  return 1    echo "t1=${t1}"    local t2=$(exit 1)    echo $? #  return 0    echo "t2=${t2}"    local t3    t3=$(exit 1)    echo $?  #  return 1    echo "t3=${t3}"}func()