NetNews Usenet Archive 1992 #18/NN_1992_18.iso/spool/comp/unix/question/10096

Text File | 1992-08-14 | 2.9 KB | 99 lines

Newsgroups: comp.unix.questions
Path: sparky!uunet!haven.umd.edu!darwin.sura.net!jvnc.net!princeton!mccc!pjh
From: [e-mail] (Pete Holsberg)
Subject: Re: Associative arrays in [gn]awk --whynot! (long but interesting)
Organization: The College On The Other Side Of Route One
Date: Fri, 14 Aug 1992 17:39:52 GMT
Message-ID: <[e-mail]>
References: <[e-mail]>
Lines: 88

In article <[e-mail]> [e-mail] (John Navarra) writes:
=Well, after my previous posting on [gn]awk associative arrays I decided
=to spend a little time investigating them. Here is what I came  up with.

=======================
=Here is a program that makes an associative array between the first and
=fifth fields of a /etc/passwd-like file.
=
=awk '
=BEGIN { FS=":"}
=
={
=#make asscociative array from first and fifth fields
=fullname[$1]=$5
=}
=END {
=   for ( username in fullname)
=           printf("%-10s %s \n", username,  fullname[username]);
=}' short.passwd
=
=awk:    results with just 15 numbers (from above)
=1root      Operator        13
=11pib      Philip Burns        2
=5usenet    Mr. Usenet          14
=7accman    Account Manager      3
=14dave     Dave Wenger        15
=6server    Mr. Listserv        4
=13len      Leonard Evens    5
=12jln      John Norstad        6
=3games     Mr. Games        7
=4ftp       Mr. ftp        8
=10mccoy    James McCoy        9
=9matt      Matthew Larson    10
=8nims      Christopher Nims    11
=2news      Mr. News        12
=15navarra  John Navarra     1
=
=nawk:
=12jln      John Norstad        2
=7accman    Account Manager    3
=4ftp       Mr. ftp        4
=10mccoy    James McCoy        5
=14dave     Dave Wenger        6
=11pib      Philip Burns        7
=5usenet    Mr. Usenet        8
=2news      Mr. News        9
=6server    Mr. Listserv        10
=1root      Operator        11
=8nims      Christopher Nims    12
=3games     Mr. Games        13
=15navarra  John Navarra        14
=9matt      Matthew Larson    15
=13len      Leonard Evens    1
=
=gawk:
=10mccoy    James McCoy        1
=6server    Mr. Listserv        2
=5usenet    Mr. Usenet        3
=15navarra  John Navarra        4
=4ftp       Mr. ftp        5
=12jln      John Norstad        6
=9matt      Matthew Larson    7
=11pib      Philip Burns        8
=13len      Leonard Evens    9
=14dave     Dave Wenger        10
=3games     Mr. Games        11
=8nims      Christopher Nims    12
=2news      Mr. News        13
=7accman    Account Manager    14
=1root      Operator        15
=
=    This is truly weird.

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.

=Basically, associative arrays in gn[awk] are
=unreliable (especially for a multi-field file).

Unreliable? In what way?

=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".