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@@ -0,0 +1,78 @@
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+#! /bin/bash
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+# explore/demonstrate scoping in bash
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+
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+unset FOO
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+
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+#
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+# Testing scoping of variables to/from functions
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+#
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+
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+
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+# Q: Do functions inherit variables from outer scope?
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+#
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+FOO=FOO-outside
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+function baz { echo FOO is $FOO; }
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+baz
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+# output is "FOO-outside".
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+#
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+# A: yes. $FOO comes from outer scope
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+
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+# Q: when does variable expansion happen
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+#
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+FOO=FOO-outside2
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+baz
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+# output is "FOO-outside2"
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+#
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+# A: expansion of $FOO hapens at baz runtime, not when defined.
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+
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+# Q: are variables global?
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+#
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+function blort { FOO=foo-inside; echo FOO inside is $FOO; }
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+echo $FOO
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+# FOO is "inside before calling the function"
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+blort
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+# ouput is "FOO inside is foo-inside"
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+echo $FOO
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+# output is "foo-inside"
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+#
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+# A: scope of of variableis global
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+
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+#
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+# Exporting variables to subshells
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+#
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+$ export -p | grep FOO
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+$ # FOO is not exported
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+
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+$ FOO=bar
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+$ export -p | grep FOO
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+$ # FOO is still not exported
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+
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+$ export FOO=baz
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+$ export -p | grep FOO
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+declare -x FOO="baz"
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+# Q: but as we see below, non-exported variables are
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+# inherited by subproceses (probably as a conseuqence
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+# of fork(2). When are exports neeed?
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+
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+
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+#
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+# Testing scoping of varibles in subshells
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+#
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+
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+# Q: are variable in a sub-shell local to that shell?
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+unset FOO
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+FOO=bar
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+function blort {
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+ (
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+ echo FOO inside blort is $FOO;
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+ FOO=foo-inside;
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+ echo FOO inside blort is $FOO after setting
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+ )
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+}
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+blort
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+echo FOO outside blort after call to baz is $FOO
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+# A: yes. FOO did not change outside the function.
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+#
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+# Commentary. This seems like a "safe" way to
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+# lmit namespace pollution and side-effects in bash,
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+# as long as you don't find the fork/exec overhead.
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