[ILUG] Bash using locally scoped vars inside while loop.

[Kevin O' Riordan]

Hi folks,

when I use a while loop to read piped input, bash seems to use locally
scoped variables instead of assigning to global variables in that
script.  So far I've only seen this when I pipe data to a while loop.

I've put together a script that should explain this a lot better than
I'm doing.  Basically I'm wondering if I'm seeing a feature, a bug, or
what.  I'm searching thru the bash bug archives at the mo', and just
wondering if anyone else has come across this before.

I'm using bash 2.04.21 here.

cheers
-kev


########################################################################

#!/bin/bash

some_var="InitString"     # Initialize some_var.

echo ""

echo "while:"
echo "  BEFORE: $some_var"  # some_var before while.
i=0
while [ $i -lt 3 ]; do
    some_var="$some_var $i" # Assign to some_var inside while.
    echo "    in while: $some_var"
    i=$((i+1))
done
echo "  AFTER: $some_var"   # some_var has been changed, as expected.

echo ""

some_var="InitString"
echo "pipe to while:"
echo "  BEFORE: $some_var"      # some_var before pipe to while.
seq 1 3 | while read i; do
    some_var="$some_var $i"     # Assign to some_var ...
    echo "    in while: $some_var"  # ... show that some_var is changed.
done
echo "  AFTER: $some_var"       # Why is some_var unchanged here ?

echo ""

########################################################################

-- 
    The majority of the stupid is invincible and guaranteed for
    all time.  The terror of their tyranny, however, is alleviated
    by their lack of consistency.
        - Albert Einstein