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Saturday, June 21, 2008

Posted by venu k
2 comments | 12:44 AM

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

# Not declared as local.
# 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

# Visible only within the function block
# 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.

2 comments:

  1. Very good article...Thanks

    ReplyDelete
  2. Well post its tell us how to make math diagrams with new method i really like this thanks for share it sop editing service .

    ReplyDelete