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Severe Bash Bug with Arrays


From: Ted Okuzumi
Subject: Severe Bash Bug with Arrays
Date: Tue, 24 Apr 2012 16:21:05 -0700

I am writing this e-mai to report to report a bug in bash.

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64'
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-unknown-linux-gnu'
-DCONF_VENDOR='unknown' -DLOCALEDIR='/usr/local/share/locale'
-DPACKAGE='bash' -DSHELL -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib
-g \
-O2
uname output: Linux concour5 2.6.18-274.3.1.el5xen #1 SMP Tue Sep 6
20:57:11 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-unknown-linux-gnu

Bash Version: 4.2
Patch Level: 0
Release Status: release

Description:
        Cannot redirect into an array from multiline variable

Does not work:
echo "$mydata" | while read line; do myarray+=( "$line" ); done


Works:
while read -r line; do myarray+=( "$line" ); done < <(echo "$mydata")


Repeat-By:
Here is exact code that shows the bug.  I create a multiline variable

mydata="aaa aaaa aaaaa
bbb bbbb bbbbb
ccc cccc ccccc"

Trying to place the file into an array fails.
Technique 1)
echo "$mydata" | while read -r line; do myarray+=( "$line" ); done

This fails.  It should work but doesn't.  This is a bug in bash.

Fix:

Technique 2)
while read -r line; do myarray+=( "$line" ); done < <(echo "$mydata")

This works

Technique 3)
Create a file foo
echo "$mydata" > foo
while read -r line; do myarray+=( "$line" ); done < foo

This works, but requires using external files which is undesired.

You can view what is in the array with this command:
echo "address@hidden"

Please let me know if I can provide any more information about the bug.  It
is easily reproducible with the code I have included.


For your convenience, here is a little script which summarizes the above.

#! /bin/bash

#First creating a multiline data file
mydata="aaa aaaa aaaaa
bbb bbbb bbbbb
ccc cccc ccccc"

# Populating the Array with mydata using technique 1
echo "Poplulating the Array using technique 1"
unset myarray
echo "$mydata" | while read -r line; do myarray+=( "$line" ); done
echo "address@hidden"
# THERE IS NO OUTPUT.  THIS IS A BUG WITH BASH

read -n1 -r -p "Press any key to continue..." key ; echo ""


# Poplulating the Array with mydata using technique 2
echo "Poplulating the Array using technique 2"
unset myarray
while read -r line; do myarray+=( "$line" ); done < <(echo "$mydata")
echo "address@hidden"
# This works

read -n1 -r -p "Press any key to continue..." key ; echo ""

# Poplulating the Array with mydata using technique 3
echo "Poplulating the Array using technique 3"
echo "$mydata" > foo
unset myarray
while read -r line; do myarray+=( "$line" ); done < foo
rm foo
echo "address@hidden"
# This works but requires using files, which is undesired


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