Monday, April 24, 2017
Bash variables scope
Bash variables scope
Bash variables are defaults to global
What makes a variable local?
- A variable declared as local is one that is visible only within the block of code in which it appears. It has local "scope." In a function, a local variable has meaning only within that function block.
Ex:
local variable name
func ()
{
local loc_var=23
# Declared as local variable.
# Uses the local builtin.
echo ""loc_var" in function = $loc_var"
global_var=999
# Defaults to global.
echo ""global_var" in function = $global_var"
}
func
# Now, to see if local variable "loc_var" exists outside function.
echo ""loc_var" outside function = $loc_var"
# $loc_var outside function =
# No, $loc_var not visible globally.
echo ""global_var" outside function = $global_var"
# $global_var outside function = 999
# $global_var is visible globally.
exit 0
- Before a function is called, all variables declared within the function are invisible outside the body of the function, not just those explicitly declared as local
func ()
{
global_var=37
# before the function has been called.
} # END OF FUNCTION
echo "global_var = $global_var"
# global_var =
# Function "func" has not yet been called,
# so $global_var is not visible here.
func
echo "global_var = $global_var"
# global_var = 37 Has been set by function call.
- Using the declare builtin restricts the scope of a variable
foo ()
{
FOO="bar"
}
bar ()
{
foo
echo $FOO
}
bar
# Prints bar
However . . .
foo (){
declare FOO="bar"
}
bar ()
{
foo
echo $FOO
}
bar
# Prints nothing.
Available link for download
