Re: possible compgen bug

[Chet Ramey]

Nicholas Mc Guire wrote:

> probably errornous behavior:
> ----------------------------
>
> when using compgen to allow shortcuts (in the below example for quit and
> exit I get a strange behavior when no input is entered and write times
> out after 5 seconds:
>
> #! /bin/bash
>
> read -p "timeout 5 > " -t 5 FOO
> CMD=( $(compgen -W "quit exit" -- $FOO) )
>
> if [ "$CMD"x == exitx ] ; then
>    echo exiting
>    $CMD
> elif [ "$CMD"x == quitx ] ; then
>    echo quit not a valid command calling exit with -1
>    exit -1
> else
>    echo invalid command - exiting with -2
>    exit -2
> fi
>
> hofrat@backup:~/shell$ ./2.sh
> timeout 5 > quit not a valid command calling exit with -1
> hofrat@backup:~/shell$
>
> it seems to expand CMD to quit - not the behavior I expected
>
> I assume that this is a bug in compgen as it indentifies an empty string
> with the first word in the options passed - I would have expected it to be
> a null-string (just as if one would type x, which has no match, thus the
> null-string is assigned to CMD)

When it is not supplied any word to complete, compgen displays all
possible completions -- in this case, the words supplied to `-W'.  This
is what happens when you perform filename completion after no characters
have been typed, for instance.  You can see this by running the compgen
command:

$ compgen -W "quit exit" -- $FOO
quit
exit


Since the assignment to CMD makes it an array, it as if you assigned
CMD=(quit exit).

You use $CMD in the rest of the script, which is the same as ${CMD[0]},
or `quit'.

Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                       Live Strong.  No day but today.
Chet Ramey, ITS, CWRU    chet@case.edu    http://cnswww.cns.cwru.edu/~chet/