On Wed, Dec 05, 2018 at 08:09:30AM +0100, Andreas Kusalananda Kähäri wrote:
> On Wed, Dec 05, 2018 at 06:14:34AM +0200, Lars Noodén wrote:
> > I'm noticing some trouble with branching in sed(1) now. Leaving the
> > label empty should branch to the end of the script:
> >
> > [2addr]b [label]
> > Branch to the : function with the specified label. If the
> > label
> > is not specified, branch to the end of the script.
> >
> > However, in practice, when I try branching without a label, I get an
> > error about an undefined label instead of it branching to the end of
> > the script:
> >
> > $ echo -e "START\nfoo\nbar\nEND\nbaz\n" | sed -n '/^START/,/^END/b;p;'
> > sed: 1: "/^START/,/^END/b;p;": undefined label ''
> >
> > Adding a label works as expected:
> >
> > $ echo -e "START\nfoo\nbar\nEND\nbaz\n" | sed -n '/^START/,/^END/ba;p;:a;
>
> No, adding the newlines makes it work. The label has nothing to do with
> it.
Sorry, too early in the morning to be reading code and make a difference
between code and data, inserting a label seems to make it work (but
I'm unsure why; sure, it's convenient, but why do we have it?) Still,
a portable sed script should have a newline after the "b" (and ":")
commands, not a semicolon.
>
> The label (empty or not) has to be delimited by a newline. In your
> first script, you could also have used
>
> sed -n -e '/^START/,/^END/b' -e p
>
> (each -e inserts a newline in the script), or more simply
>
> sed '/^START/,/^END/d'
>
> This is AFAIK standard behaviour.
>
> >From POSIX:
>
> Command verbs other than {, a, b, c, i, r, t, w, :, and # can be
> followed by a <semicolon>, optional <blank> characters, and
> another command verb.
>
>
> Andreas
>
> >
> > If I have not made a mistake with the short script above then there
> > seems to be a discrepancy between the behavior described in the manual
> > and the actual behavior.
> >
> > dmesg below
> > /Lars
> >
[cut]
--
Andreas Kusalananda Kähäri,
National Bioinformatics Infrastructure Sweden (NBIS),
Uppsala University, Sweden.
