Bug#301433: acknowledged by developer (Re: Bug#301433: bash: variables revert to original values when exiting loop involving read)

Sat, 26 Mar 2005 01:08:13 -0800

Huh? That doesn't sound like any shell I've used over the past 25 years, including bash. The only thing I find in the manpage about variable scoping is using the local declaration inside functions.

If I change the while loop to be a for loop:

        for f in first second ;do

I get the expected results, namely that the final value is 'second', not 'initial'.

It also works if I take out the read, e.g.,:

        cat <<-EOF >/tmp/ttt
                first line
                second line
                EOF
        val=initial
        typeset -i line=1
        while true ;do
            val=$(sed -n "${line}p" /tmp/ttt | awk '{print $1}')
            echo "$line val is '$val'"
            test -n "$val"  ||  break
            ((line += 1))
        done
        echo "final val is '$val'


I'm not an expert in bash, and you obviously are, so quite possibly I'm missing something. Could you please show me the part of the manpage that I need to read to obtain enlightenment?

P.S.  My test program is attached.

NHA
---
Norman H. Azadian    Taegerishalde 13    CH-3110 Muensingen    Switzerland
[EMAIL PROTECTED]      tel: +41 31 721 7855      fax: +41 31 55 898 55


Debian Bug Tracking System wrote: 
This is an automatic notification regarding your Bug report
#301433: bash: variables revert to original values when exiting loop involving 
read,
which was filed against the bash package.

It has been closed by one of the developers, namely
Matthias Klose <[EMAIL PROTECTED]>.

Their explanation is attached below.  If this explanation is
unsatisfactory and you have not received a better one in a separate
message then please contact the developer, by replying to this email.

Debian bug tracking system administrator
(administrator, Debian Bugs database)

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Date: Fri, 25 Mar 2005 23:29:14 +0100
To: "Norman H. Azadian" <[EMAIL PROTECTED]>, [EMAIL PROTECTED]
Subject: Re: Bug#301433: bash: variables revert to original values when exiting loop involving read
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Norman H. Azadian writes:

Package: bash
Version: 2.05b-24
Severity: important

The following script illustrates the problem:

        #!/bin/sh

        val=initial
        cat <<-EOF | while read ;do
                first line
                second line
                EOF
            val=$REPLY
            echo "val is '$val'"
        done
        echo "final val is '$val'"

When I run this, I get:

        val is 'first line'
        val is 'second line'
        final val is 'initial'

I suspect this only happens with read, but I'm not sure.


not a bug, the variable is set in another process (while ... done) 
#!/bin/bash

echo === Test 1
val=initial
cat <<-EOF | while read ;do
        first line
        second line
        EOF
    val=loop
    echo "val is '$val'"
done
echo "final val is '$val'"


echo === Test 2
val=initial
cat <<-EOF | while read ;do
        first line
        second line
        EOF
    val=$REPLY
    echo "val is '$val'"
done
echo "final val is '$val'"


echo === Test 3
for f in first second ;do
    val=$f
    echo "val is '$val'"
done
echo "final val is '$val'"


echo === Test 4
cat <<-EOF >/tmp/ttt
        first line
        second line
        EOF
val=initial
typeset -i line=1
while true ;do
    val=$(sed -n "${line}p" /tmp/ttt | awk '{print $1}')
    echo "$line val is '$val'"
    test -n "$val"  ||  break
    ((line += 1))
done
echo "final val is '$val'"

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