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Re: [bug-gawk] When RS is null, POSIX states \n should be in FS, gawk on
From: |
arnold |
Subject: |
Re: [bug-gawk] When RS is null, POSIX states \n should be in FS, gawk only does that if FS is single char |
Date: |
Mon, 15 Apr 2019 07:52:51 -0600 |
User-agent: |
Heirloom mailx 12.5 7/5/10 |
Hi.
Thanks for the report. This smells like a change in the POSIX
standard, but I will have to research previous standards and also
what the original AWK book says.
Thanks,
Arnold
Ed Morton <address@hidden> wrote:
> I just came across this where setting RS to null causes FS to include
> `\n` if FS is a singe char but not otherwise:
>
> $ printf '1:2\n3\n' | awk -F':' -v RS= '{for (i=1; i<=NF; i++) print
> i"/"NF, "<"$i">"}'
> 1/3 <1>
> 2/3 <2>
> 3/3 <3>
>
> $ printf '1::2\n3\n' | awk -F'::' -v RS= '{for (i=1; i<=NF; i++)
> print i"/"NF, "<"$i">"}'
> 1/2 <1>
> 2/2 <2
> 3>
>
> with this gawk version:
>
> $ awk --version
> GNU Awk 4.2.1, API: 2.0 (GNU MPFR 4.0.2, GNU MP 6.1.2)
> Copyright (C) 1989, 1991-2018 Free Software Foundation.
>
> and that makes sense given the gawk documentation
> (https://www.gnu.org/software/gawk/manual/gawk.html#Multiple-Line) which
> says (red/underline mine):
>
> When RS is set to the empty string _/and /__FS is set to a single
> character_, the newline character always acts as a field separator.
> This is in addition to whatever field separations result from FS^
>
> but the POSIX spec (http://pubs.opengroup.org/onlinepubs/9699919799/) says:
>
> *RS*
> The first character of the string value of *RS* shall be the
> input record separator; a <newline> by default. If *RS* contains
> more than one character, the results are unspecified. If *RS* is
> null, then records are separated by sequences consisting of a
> <newline> plus one or more blank lines, leading or trailing
> blank lines shall not result in empty records at the beginning
> or end of the input, and a <newline> shall always be a field
> separator, no matter what the value of *FS* is.
>
> gawk behaves the way I described with or without the `--posix` flag.
> Shouldn't it add `\n` as a separator when RS is null regardless of the
> value of FS like POSIX says? FWIW OSX/BSD awk on MacOS behaves the same
> way that gawk does, idk about other awks.
>
> ???????? Ed.