NetNews Usenet Archive 1992 #18/NN_1992_18.iso/spool/comp/unix/question/10098

Text File | 1992-08-14 | 2.7 KB | 112 lines

Newsgroups: comp.unix.questions
Path: sparky!uunet!cs.utexas.edu!wupost!zaphod.mps.ohio-state.edu!news.acns.nwu.edu!casbah.acns.nwu.edu!navarra
From: [e-mail] (John Navarra)
Subject: Re: Associative arrays in [gn]awk --whynot! (long but interesting)
Message-ID: <[e-mail]>
Sender: [e-mail] (Usenet on news.acns)
Organization: Northwestern University, Evanston Illinois.
References: <[e-mail]> <[e-mail]>
Date: Sat, 15 Aug 1992 02:19:54 GMT
Lines: 100

In article <[e-mail]> [e-mail] (Pete Holsberg) writes
>In article <[e-mail]> [e-mail] (John Navarra) writes:
>=======================
>=Here is a program that makes an associative array between the first and
>=fifth fields of a /etc/passwd-like file.
>
>Where did the values in the third field of the output come from? What's
>weird about the first two columns? It seems to me that they match
>insofar as the index and the value go.

    The third field was a replication of the results from printing out
the values stored in the array for a 15 line file (numbered 1-15). I just
wanted to point out the a one column (or one-field per line file) is output
differently than a multi-column (or multi-field per line) file with each
of the programs awk, nawk, and gawk.

>=Basically, associative arrays in gn[awk] are
>=unreliable (especially for a multi-field file).
>
>Unreliable? In what way?

    With respect to order being read in. Obviously, many of you know
that this is a well-known bug. Some do not. However, gawk, which you may
expect to print out the values correctly (i.e in numerical order) only
prints those values correctly if the file is in numerical order in the first
place. This is not always going to be the situation!

>
>=Gawk seems to be the
>=best at printing out arrays in the order which they were loaded in but
>=it does not do it correctly in all cases.
>
>Order in "for (index in array)" is not specified by awk. If you need
>order, pipe the output to "sort".

    Yeah, but what if sort doesn't cut it? For instance, say I had the
file:

2
1
4
3
6
5
8
7
10
9
12
11
14
13
15

and I ran my program on it:
$ gawk -f showarray 15nums.mixed
2
1
4
3
6
5
8
7
10
9
12
11
14
13
15

This is not the correct order.
$ gawk -f showarray 15nums.mixed | sort -n
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

    and this is not the correct order either. I *want* the output to
be printed in the *same* order it was read in!!! Now tell me how to do
that with sort if the numbers aren't in some order sort understands?
Now see where the problem is?

-tms
--
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