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Re: weird problem -- path interpretted/eval'd as numeric expression


From: Greg Wooledge
Subject: Re: weird problem -- path interpretted/eval'd as numeric expression
Date: Fri, 29 Mar 2013 11:36:44 -0400
User-agent: Mutt/1.4.2.3i

On Fri, Mar 29, 2013 at 04:10:22PM +0100, John Kearney wrote:
> consider
> address@hidden ~
> $ read -ra vals -d '' <<< $'lkjlksda\n adasd\n:sdasda:'
> 
> address@hidden ~
> $ echo ${vals[0]}
> lkjlksda

You forgot to set IFS=: for that read.

imadev:~$ IFS=: read -ra vals -d '' <<< $'lkjlksda\n adasd\n:sdasda:'
imadev:~$ declare -p vals
declare -a vals='([0]="lkjlksda\
 adasd\
" [1]="sdasda" [2]="\
")'

> I meant to update your wiki about it but I forgot.
> I guess read uses gets not fread and that truncates the line anyway.

No, that's not correct.

> >> cat <<EOF ><known_path>/source_wrapper.sh
> >>     find_file "${1:?Missing File Name }" || return $?
> >>     source "${FOUND_FILE}"
> >> EOF
> >> alias include=source\ "<known_path>/source_wrapper.sh"

> > The <<EOF needs to be <<'EOF' (or similar), and of course you have to
> > include the definition of find_file in the wrapper script.

> ?? why <<'EOF' ??

Because if you don't quote any of the characters in the here document
delimiter, the expansions such as "${FOUND_FILE}" will be done by the
shell that's processing the redirection.  I believe you want the code
to appear in the output file.  Therefore you want to quote some or all
of the characters in the delimiter.

Compare:

imadev:~$ cat <<EOF
> echo "$HOME"
> EOF
echo "/net/home/wooledg"

imadev:~$ cat <<'EOF'
> echo "$HOME"
> EOF
echo "$HOME"

On Fri, Mar 29, 2013 at 04:18:49PM +0100, John Kearney wrote:
> Oh and FYI
> IFS=: read
> may change the global IFS on some shells I think.
> Mainly thinking of pdksh right now.

If those shells have such a bug, then you'd need to bring it up on THEIR
bug mailing list.  This is bug-bash. ;-)

In any case, I've never seen such a bug, and the pdksh to which I have
access does not display it:

...
Get:1 http://ftp.us.debian.org/debian/ squeeze/main pdksh i386 5.2.14-25 [265 
kB]
...
arc3:~$ pdksh
\h:\w$ echo a:b:c > /tmp/frob
\h:\w$ IFS=: read a b < /tmp/frob
\h:\w$ rm /tmp/frob
\h:\w$ echo "$IFS"
        

\h:\w$ 

This is a fundamental feature that's commonly used.  If it were so
egregiously broken I think more people would have noticed it.



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