* pairwise concatenation (a winner)
@ 1991-08-30 15:36 Paul Haahr
0 siblings, 0 replies; only message in thread
From: Paul Haahr @ 1991-08-30 15:36 UTC (permalink / raw)
To: rc
and the winner is... Malte.
after upping the prize and offering a cash alternative, i actually got
responses. (2 even!) both arrived within a day or two of my announcing
raised stakes, and within an hour or so of each other. Byron and i
picked this one as the winner. [this note should have gone out a couple
of days ago, but i've been swamped getting things done at the office before
leaving on vacation today.]
here's Malte's note:
> I recently discovered a useful application for pairwise concatenation. I use
> in a set of shell scripts that helps me adding users to our LAN.
> While applying different checks on the consistency of the group and
> passwd database I split up their entries and assign them to variables to
> avoid frequent calling of cut, sed, grep, awk, ...
>
> acct=`{cut -f1 -d: /etc/passwd}
> pswd=`{cut -f2 -d: /etc/passwd} ...
>
> After doing the checks I reconcatenate passwd by using
>
> output=($acct)^':'^($pw)^':'^($uid) ...
> and then
> for( i in $output ){ echo $i }
>
> This is quite specific and probably of little help to non-sysops.
> But being more general:
> pairwise concatenation gives you a tool (device?) which helps
> simulating two dimensional arrays. As a special application
> it provides access methods for simple relational databases,
> as is /etc/passwd and /etc/group, where the relation is the
> gid-field.
>
> I haven't spent much thought on that, but I guess there are several
> situations where this is applicable, one just doesn't see them because
> being still to deep into bourne shell.
as a side note, i should add that i actually found use for pairwise
concatenation this week, when i discovered that NeXT does not ship
cut and paste with their machines. ^ is a reasonably good substitute
for paste, which is part of how Malte suggests using it.
now the important question: do these uses provide a good enough justification
for leaving pairwise concatenation in rc, except for backward compatibility
reasons? in our oh-so-clean, minimalist shell, (not, imho, a "spartan toy")
is this a worthwhile feature?
that said, congratulations Malte! i'll have a check in the mail as
soon as i can figure how to convert it to marks. (and where to send
it, given i don't know your address or last name.)
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1991-08-30 15:36 pairwise concatenation (a winner) Paul Haahr
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