Re: Question about a programme

On 2/18/2008 6:57 AM, Spiros Bousbouras wrote:
> On page 194 of "Effective AWK programming" we see the
> following programme:
> 
> # rewind.awk --- rewind the current file and start over
> function rewind(    i)
> {
>     # ****ft remaining arguments up
>     for (i = ARGC; i > ARGIND; i--)
>         ARGV[i] = ARGV[i-1]
>     # make sure gawk knows to keep going
>     ARGC++
>     # make current file next to get done
>     ARGV[ARGIND+1] = FILENAME
>     # do it
>     nextfile
> }
> 
> Isn't the statement ARGV[ARGIND+1] = FILENAME
> superfluous ? In the loop when i gets the
> value ARGIND + 1 then the assignment
> ARGV[ARGIND + 1] = ARGV[ARGIND] will be executed
> and ARGV[ARGIND] always has the same value as
> FILENAME

But what if the current file is the last one? Then i = ARGC = ARGIND at
the
start of the loop, so the loop's never entered so THEN that final
assignment is
required. Although that works in this context since the functiona name
implies
it MUST be called while parsing a file, use of FILENAME meanse you can't
execute
this type of general "****ft the arguments" function in a BEGIN section so
I'm
not a big fan.

Personally, I expect I'd have written it as:

# rewind.awk --- rewind the current file and start over
function rewind(    i)
{
    # ****ft remaining arguments up
    for (i = ++ARGC; i > ARGIND; i--)
        ARGV[i] = ARGV[i-1]
    # do it
    nextfile
}

(leaving out the "nextfile" for a general "****ft" function) but I haven't
thought about it much and maybe there was something else the author was
trying
to show with that example...

	Ed.