Re: Is this an IFS bug in getopts?

[Steven W. Orr]

On 4/26/2011 12:02 PM, DJ Mills wrote:
> On Tue, Apr 26, 2011 at 11:42 AM, Steven W. Orr<steveo@syslang.net>  wrote:
>
> > GNU bash, version 4.0.35(1)-release (x86_64-redhat-linux-gnu)
> >
> > I ran a program that was supposed to die with an error message that said:
> >
> > Invalid format: example: 2.103.269.28-1-3
> >
> > Instead, it died with:
> >
> > i -- Invalid format: example: 2.103.269.28-1-3
> >
> > I traced the problem back to a call to getopts. It turns out that when I
> > called getopts, I had set IFS='-'. It never occurred to me that I could
> > impact the function of getopts by setting IFS.
> >
> > The old code was this:
> > DRVREV="$1"
> > IFS=-
> > set -- $DRVREV
> > (( $# == 3 )) || die -i -- 'Invalid format: example: 2.103.269.28-1-3'
> >
> > I can fix the problem easily by saying
> >
> > oldIFS="$IFS"
> > DRVREV="$1"
> > IFS=-
> > set -- $DRVREV
> > IFS="$oldIFS"
> > (( $# == 3 )) || die -i -- 'Invalid format: example: 2.103.269.28-1-3'
> >
> > So here we are.
> > 1. Should getopts be documented to say that it uses IFS?
> > 2. Should getopts be hardcoded to use the dash as the option delimiter?
> > 3. Is the current functionality correct the way it is and I'm just looking
> > at it wrong?
> >
> > TIA :-)
>   I don't see getopts anywhere in that example.  It would also help to know
> what your
> die() function is, as I suspect that may be causing the issue.

Fair enough.

err was created as a simple echo that went to stderr. Then I added -i so that 
it would allow itself to read from stdin after it processed its arguments.

die is just a call to err followed by a call to exit. It captures the -i and 
passes it through to err. It also accepts a -s to specify an exit code.

Also, the die call is routinely made with -- because sometimes the args to be 
echoed can begin with a -.

err()
{
    typeset opt
    typeset opt_i=0
    OPTIND=1
    while getopts ':-i' opt "$@"
    do
        case $opt in
        i)
            opt_i=1
            ;;
        *)
            echo "Illegal option to err: ${@:((OPTIND-1)):1}" 1>&2
            exit 1
            ;;
        esac
    done
    shift $((OPTIND-1))
    (( $# != 0 )) && echo -e "$@" 1>&2
    (( opt_i )) && cat 1>&2
}

die()
{
    typeset opt
    typeset opt_s=1
    typeset opt_i=0
    typeset err_opts=
    OPTIND=1
    while getopts ':is:' opt "$@"
    do
        case $opt in
        i)
            opt_i=1
            err_opts='-i'
            ;;
        s)
            opt_s=$OPTARG
            ;;
        *)
            err "Illegal option to die: ${@:((OPTIND-1)):1}"
            exit 1
            ;;
        esac
    done
    shift $((OPTIND-1))
    err $err_opts -- "$@"
    exit $opt_s
}



--
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steveo at syslang.net