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read with parameter expansion in here string

From: Clint Hepner
Subject: read with parameter expansion in here string
Date: Fri, 22 Nov 2013 09:22:35 -0500

Configuration Information [Automatically generated, do not change]:
Machine: i386
OS: darwin13.0.0
Compiler: clang
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i386' 
-DCONF_OSTYPE='darwin13.0.0' -DCONF_MACHTYPE='i386-apple-darwin13.0\
.0' -DCONF_VENDOR='apple' 
-DLOCALEDIR='/usr/local/Cellar/bash/4.2.45/share/locale' -DPACKAGE='bash' 
COSX   -I.  -I. -I./include -I./lib -I./lib/intl 
-I/private/tmp/bash-4vKN/bash-4.2/lib/intl  -DSSH_SOURCE_BASHRC
uname output: Darwin patikoija.local 13.0.0 Darwin Kernel Version 13.0.0: Thu 
Sep 19 22:22:27 PDT 2013; root:xnu-2422.1.72~6/REL\
EASE_X86_64 x86_64
Machine Type: i386-apple-darwin13.0.0

Bash Version: 4.2
Patch Level: 45
Release Status: release


        An unquoted parameter expansion in a here string does not seem to 
conform with my understanding of how
        read works with a local IFS override. Personally observed in bash 
3.2.51, 4.1.2 as well. I first learned
        of this possible bug via http://stackoverflow.com/q/20144593/1126841.

        $ var="hello:world"

        # Case (1) I would expect "hello:world" in var1 if $var isn't split, or 
        # if it is. World splitting seems to occur after var1 is set, which 
        # seem to make sense.
        $ IFS=: read var1 var2 <<< $var
        $ echo "$var1"
        hello world
        # Case (2) Expected behavior, consistent with case (3)
        $ IFS=: read var1 var2 <<< "$var"
        $ echo "$var1"

        # Case (3) - no parameter expansion involved with the read
        $ IFS=: read var1 var2 <<< hello:world
        $ echo "$var1"

        # Case (4) - an explicit here document instead of a here string
        $ IFS=: read var1 var2 <<EOF
        > $var
        > EOF
        $ echo "$var1"

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