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shellloopsunset

Loop Variables and `unset` in Shell Script

I just wanted to confirm here since I've only tested in dash shell, but do loop variables collide with variables in the outer scope in shell scripts in general? For example

#! /bin/sh

i='1 2 3'
a='a b c'

for i in $a; do
  echo "$i"
done

echo "$i"

This outputs:

a
b
c
c

which makes sense to me. That is, it seems to indicate that I'm right that loop variables will collide (they share the same namespace as the outer scope). I want to know because if I'm using an older-style shell that doesn't have the local command, I want to be sure to unset loop variables I use in functions. The texts I've read cover unset, but don't seem to cover this case.

Am I right?

Solution

  • You to avoid namespace issues .. You can fork your script and put the loop inside that fork ..

    #! /bin/sh

i='1 2 3'
a='a b c'

function_to_fork(){
  for i in $a; do
     echo "$i"
  done
}

(function_to_fork)

echo "$i"