Re: alternation option end of string
"Mark J. Reed" <[email protected]> Sun, 3 May 2026 20:01:17 -0400
| Newsgroups | gmane.comp.shells.zsh.user |
|---|---|
| Message-ID | <CAA=-s3w2Ms1dF3KxGU3qzg-+QLazyQWZRxg5NoWsRpOYRC7FqA@mail.gmail.com> |
--000000000000f47e460650f2a15c
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
What you really want is to _remove_ whatever comes after either "cats" or,
if the thing after "cat" is not an s, "cat".
But if you're reading comma-separated fields, you can just use `read`:
IFS=3D, read base idx comment <<<"$INPUT"
e.g.
for INPUT in file file, file,8 file,88 file,8,comment file,88,comment \
file,8a file,a8 file,a8,comment file,8a,comment
file,8a,com,ment \
file,8,com,ment file,8,comm,9 file,8,comm,9a file,8,comm,a9; d=
o
IFS=3D, read base idx comment <<<"$INPUT"
printf '\n%8s: %s\n' INPUT "$INPUT"
printf '%8s:\t%s\n' base "$base"
printf '%8s:\t%s\n' idx "$idx"
printf '%8s:\t%s\n' comment "$comment"
done
INPUT: file
base: file
idx:
comment:
INPUT: file,
base: file
idx:
comment:
INPUT: file,8
base: file
idx: 8
comment:
INPUT: file,88
base: file
idx: 88
comment:
INPUT: file,8,comment
base: file
idx: 8
comment: comment
INPUT: file,88,comment
base: file
idx: 88
comment: comment
INPUT: file,8a
base: file
idx: 8a
comment:
INPUT: file,a8
base: file
idx: a8
comment:
INPUT: file,a8,comment
base: file
idx: a8
comment: comment
INPUT: file,8a,comment
base: file
idx: 8a
comment: comment
INPUT: file,8a,com,ment
base: file
idx: 8a
comment: com,ment
INPUT: file,8,com,ment
base: file
idx: 8
comment: com,ment
INPUT: file,8,comm,9
base: file
idx: 8
comment: comm,9
INPUT: file,8,comm,9a
base: file
idx: 8
comment: comm,9a
INPUT: file,8,comm,a9
base: file
idx: 8
comment: comm,a9
On Sun, May 3, 2026 at 4:23=E2=80=AFPM Ray Andrews <[email protected]>=
wrote:
>
>
> On 2026-05-03 11:45, Bart Schaefer wrote:
> > On Sun, May 3, 2026 at 6:56=E2=80=AFAM Ray Andrews <rayandrews@eastlink=
.ca>
> wrote:
> >> It might not actually be the '$' just some mechanism for matching a
> >> string that must end after some substring.
> > That's not what you're asking for, tho. You're asking for the entire
> > string to fail to match if there's anything after the substring, but
> > in the same pattern you want the substring itself to match so you can
> > extract it. You can't simultaneously have a failure and a success.
> > That's why Roman's solution has (compare && out=3Dsuccess ||
> > out=3Dfailure) -- there's no single pattern expression that can do both
> > branches. (There might be a perl expression that works, but I'm not
> > confident pcre is perl-ish enough to do it.)
> I thought the thing was logically possible because it can be
> articulated: 'cat' then either nothing || an 's' which can itself be
> followed by anything. But if it's not doable, as I said, no matter cuz
> the functionality is there and I'd do it Roman's way anyway cuz it's
> self-explanatory. Too much terseness already, so I wish for more
> terseness very lightly. Sorta like a while back I was wondering if:
> (( x > 5 )) && x=3D5
> ... had a more compact syntax -- if not so what, it's not a problem,
> still, sometimes zsh offers these little shortcuts.
>
>
>
>
>
--=20
Mark J. Reed <[email protected]>
--000000000000f47e460650f2a15c
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
<div dir=3D"ltr">What you really want is to _remove_ whatever comes after e=
ither "cats" or, if the thing after "cat" is not an s, =
"cat".=C2=A0<div><br></div><div>But if you're reading comma-s=
eparated fields, you can just use `read`:</div><div><br></div><div><font fa=
ce=3D"monospace">=C2=A0 =C2=A0 IFS=3D, read base idx comment <<<&q=
uot;$INPUT"</font></div><div><br></div><div>e.g.</div><div><br></div><=
div><font face=3D"monospace">for INPUT in file file, file,8 file,88 file,8,=
comment file,88,comment \<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0file,8a file,a8 file,a8,comment file,8a,comment file,8a,com,ment \<br>=
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0file,8,com,ment file,8,comm=
,9 file,8,comm,9a file,8,comm,a9; do<br>=C2=A0 IFS=3D, read base idx commen=
t <<<"$INPUT"<br>=C2=A0 printf '\n%8s: %s\n' INP=
UT "$INPUT"<br>=C2=A0 printf '%8s:\t%s\n' base "$bas=
e"<br>=C2=A0 printf '%8s:\t%s\n' idx "$idx"<br>=C2=
=A0 printf '%8s:\t%s\n' comment "$comment"<br>done</font>=
<br></div><div><br><font face=3D"monospace">=C2=A0 =C2=A0INPUT: file<br>=C2=
=A0 =C2=A0 base: file<br>=C2=A0 =C2=A0 =C2=A0idx: <br>=C2=A0comment: <br><b=
r>=C2=A0 =C2=A0INPUT: file,<br>=C2=A0 =C2=A0 base: file<br>=C2=A0 =C2=A0 =
=C2=A0idx: <br>=C2=A0comment: <br><br>=C2=A0 =C2=A0INPUT: file,8<br>=C2=A0 =
=C2=A0 base: file<br>=C2=A0 =C2=A0 =C2=A0idx: 8<br>=C2=A0comment: <br><br>=
=C2=A0 =C2=A0INPUT: file,88<br>=C2=A0 =C2=A0 base: file<br>=C2=A0 =C2=A0 =
=C2=A0idx: 88<br>=C2=A0comment: <br><br>=C2=A0 =C2=A0INPUT: file,8,comment<=
br>=C2=A0 =C2=A0 base: file<br>=C2=A0 =C2=A0 =C2=A0idx: 8<br>=C2=A0comment:=
comment<br><br>=C2=A0 =C2=A0INPUT: file,88,comment<br>=C2=A0 =C2=A0 base: =
file<br>=C2=A0 =C2=A0 =C2=A0idx: 88<br>=C2=A0comment: comment<br><br>=C2=A0=
=C2=A0INPUT: file,8a<br>=C2=A0 =C2=A0 base: file<br>=C2=A0 =C2=A0 =C2=A0id=
x: 8a<br>=C2=A0comment: <br><br>=C2=A0 =C2=A0INPUT: file,a8<br>=C2=A0 =C2=
=A0 base: file<br>=C2=A0 =C2=A0 =C2=A0idx: a8<br>=C2=A0comment: <br><br>=C2=
=A0 =C2=A0INPUT: file,a8,comment<br>=C2=A0 =C2=A0 base: file<br>=C2=A0 =C2=
=A0 =C2=A0idx: a8<br>=C2=A0comment: comment<br><br>=C2=A0 =C2=A0INPUT: file=
,8a,comment<br>=C2=A0 =C2=A0 base: file<br>=C2=A0 =C2=A0 =C2=A0idx: 8a<br>=
=C2=A0comment: comment<br><br>=C2=A0 =C2=A0INPUT: file,8a,com,ment<br>=C2=
=A0 =C2=A0 base: file<br>=C2=A0 =C2=A0 =C2=A0idx: 8a<br>=C2=A0comment: com,=
ment<br><br>=C2=A0 =C2=A0INPUT: file,8,com,ment<br>=C2=A0 =C2=A0 base: file=
<br>=C2=A0 =C2=A0 =C2=A0idx: 8<br>=C2=A0comment: com,ment<br><br>=C2=A0 =C2=
=A0INPUT: file,8,comm,9<br>=C2=A0 =C2=A0 base: file<br>=C2=A0 =C2=A0 =C2=A0=
idx: 8<br>=C2=A0comment: comm,9<br><br>=C2=A0 =C2=A0INPUT: file,8,comm,9a<b=
r>=C2=A0 =C2=A0 base: file<br>=C2=A0 =C2=A0 =C2=A0idx: 8<br>=C2=A0comment: =
comm,9a<br><br>=C2=A0 =C2=A0INPUT: file,8,comm,a9<br>=C2=A0 =C2=A0 base: fi=
le<br>=C2=A0 =C2=A0 =C2=A0idx: 8<br>=C2=A0comment: comm,a9</font><br></div>=
<div><br></div></div><br><div class=3D"gmail_quote gmail_quote_container"><=
div dir=3D"ltr" class=3D"gmail_attr">On Sun, May 3, 2026 at 4:23=E2=80=AFPM=
Ray Andrews <<a href=3D"mailto:[email protected]">rayandrews@eastl=
ink.ca</a>> wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"m=
argin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left=
:1ex"><br>
<br>
On 2026-05-03 11:45, Bart Schaefer wrote:<br>
> On Sun, May 3, 2026 at 6:56=E2=80=AFAM Ray Andrews <<a href=3D"mail=
to:[email protected]" target=3D"_blank">[email protected]</a>>=
wrote:<br>
>> It might not actually be the '$' just some mechanism for m=
atching a<br>
>> string that must end after some substring.<br>
> That's not what you're asking for, tho.=C2=A0 You're askin=
g for the entire<br>
> string to fail to match if there's anything after the substring, b=
ut<br>
> in the same pattern you want the substring itself to match so you can<=
br>
> extract it.=C2=A0 You can't simultaneously have a failure and a su=
ccess.<br>
> That's why Roman's solution has (compare && out=3Dsucc=
ess ||<br>
> out=3Dfailure) -- there's no single pattern expression that can do=
both<br>
> branches.=C2=A0 (There might be a perl expression that works, but I=
9;m not<br>
> confident pcre is perl-ish enough to do it.)<br>
I thought the thing was logically possible because it can be <br>
articulated: 'cat' then either nothing || an 's' which can =
itself be <br>
followed by anything.=C2=A0 But if it's not doable, as I said, no matte=
r cuz <br>
the functionality is there and I'd do it Roman's way anyway cuz it&=
#39;s <br>
self-explanatory.=C2=A0 Too much terseness already, so I wish for more <br>
terseness very lightly.=C2=A0 Sorta like a while back I was wondering if:<b=
r>
(( x > 5 )) && x=3D5<br>
... had a more compact syntax -- if not so what, it's not a problem, <b=
r>
still, sometimes zsh offers these little shortcuts.<br>
<br>
<br>
<br>
<br>
</blockquote></div><div><br clear=3D"all"></div><div><br></div><span class=
=3D"gmail_signature_prefix">-- </span><br><div dir=3D"ltr" class=3D"gmail_s=
ignature">Mark J. Reed <<a href=3D"mailto:[email protected]" target=3D=
"_blank">[email protected]</a>><br></div>
--000000000000f47e460650f2a15c--