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Loop control from within a subshell

I want to use subshells for making sure environment changes do not affect different iterations in a loop, but I'm not sure I can use loop control statements (break, continue) inside the subshell:

#!/bin/sh
export A=0
for i in 1 2 3; do
  (
  export A=$i
  if [ $i -eq 2 ]; then continue ; fi
  echo $i
  )
done
echo $A

The value of A outside the loop is unaffected by whatever happens inside, and that's OK. But is it allowed to use the continue inside the subshell or should I move it outside? For the record, it works as it is written, but maybe that's an unreliable side effect.

Solution

  • Just add

    echo "out $i"

    after the closing parenthesis to see it does not work - it exits the subshell, but continues the loop.

    The following works, though:

    #! /bin/bash
export A=0
for i in 1 2 3; do
    (
        export A=$i
        if [ $i -eq 2 ]; then exit 1 ; fi
        echo $i
    ) && echo $i out      # Only if the condition was not true.
done
echo $A