Discussion between Wildcard and cuonglm

Stack Exchange

07:08

4

A: What the equivalent of "grep | cut" using sed or awk?

The exact equivalent would be something like: sed -n '/email2/{s/^[^=]*=\([^=]*\).*/\1/;p;}' < file But you'd probably want instead: sed -n 's/^[^=]*email2[^=]*=[[:blank:]]*//p' < file (that is match email2 only on the part before the first = and return everything on the right of the first ...

cuonglm

Is space required between { s?

Yes, that's exactly I have stucked when working with this. After re-reading POSIX sed documentation, I see ;} is an accepted extension, but it's not required. It's strange that GNU sed with --posix option still allow {command} form. Do you think it's a bug?

Wildcard

I can't find where ;} is mentioned in the Sed POSIX specs as an accepted extension. It seems to be required by The <right-brace> shall be preceded by a <newline> or <semicolon>. @cuonglm or Stephane, could you clarify?

cuonglm

@Wildcard Yes, ;} is not POSIX, that what Stephane said in his comment above. But I remember it will be in next POSIX version, there's an issue in austin bug group.

Wildcard

@cuonglm, no, I mean I don't see it as just an extension. "The right brace shall be preceded by a newline or semicolon...." So if you precede it with a semicolon in your Sed script, haven't you followed the explicit instructions of POSIX?

@cuonglm, huh, I still don't see it in the specs. But if it will be changed in the next POSIX edition I suppose it's not critical. :)

cuonglm

@Wildcard: The austinbug group link austingroupbugs.net/view.php?id=961

@Wildcard Ops, look like the spec was changed follow that issue.

Wildcard

07:10

@cuonglm Now I'm even more confused. The only POSIX specs for Sed that I am aware of are here, and they have the older version of the line that is specified in that link you just gave. Is there a later version I'm not aware of?

cuonglm

Hmm, that's the newest one

Wildcard

@cuonglm From this link it looks like the change being discussed (and relaxed) is the requirement that a newline follow the }, not that a newline precede the }.

cuonglm

pubs.opengroup.org/onlinepubs/009695399/utilities/sed.html

that's the old one

Wildcard

@cuonglm Well at least that's clear. "The right brace shall be preceded by a newline."

cuonglm

Yes, and even in the newer version as the link you gave, I remember ;} isn't allowed

I think they made the change after that issue accepted

Wildcard

07:16

@cuonglm No, ;} is explicitly allowed: The <right-brace> shall be preceded by a <newline> or <semicolon>. But it seems that what is not allowed is ;};} because

Editing commands other than {...}, a, b, c, i, r, t, w, :, and # can be followed by a <semicolon>, optional <blank> characters, and another editing command.

That seems to be the requirement discussed in the link you gave.

@cuonglm Does that mean the change has been made, but the current issue of POSIX doesn't include it? So the next one will, for sure?

(How does that work?)

cuonglm

@Wildcard See this issue by Stephane austingroupbugs.net/view.php?id=944

and his comment

The only sensible explanation is a whole command group ({ to the matching }). As in {...;} cannot be followed by ;, but then again all implementations I tested including Unix V7 allow:

sed '{=;};{=;}'

Wildcard

@cuonglm That's very very helpful, thanks! :)

What I really meant was how do the issues of POSIX work, since the issue you linked earlier is marked "resolved" but the proposed change doesn't appear in the current Sed specs.

cuonglm

I think it does

Ah

sorry, it doesn't, as it's tagged issue 8

also, its status is resolved, not approved :D

Wildcard

@cuonglm But the resolution is "Accepted"....

cuonglm

yes, it's accepted to be included in new version, but not yet

because new version isn't there

current POSIX issue is 7

next will be 8

Anyway, I remember the question how austinbug group issue process was asked somewhere

let me check

Wildcard

07:33

@cuonglm Aha. Is version 8 visible somewhere (i.e. the currently accepted content for what will be version 8)?

cuonglm

@Wildcard AFAIK, no. You must search the austingroup bug site, with tag filter issue 8

Wildcard

And am I right in thinking this is a public tracking system, and I could create an account and open an issue if I so chose? (After searching for existing issues, considering implications, etc., etc.)

@cuonglm Got it, thanks.

cuonglm

yes, that's it

Wildcard

@cuonglm Wow, nice.

I see mention of a "conference call" in a random ticket I am reading.

Is there a doc somewhere that covers the working of the POSIX specifications group itself? Like, who puts issue 8 together from the various tickets, and who decides when it gets released? How would I end up on these conference calls?

cuonglm

There's FAQ for those questions

opengroup.org/austin/faq.html

I don't remember all, but I only know geoffclare and ajosey often accept and approve isses

and it's interesting that you will see many reporters who are in U&L

Stephane, Schily, Thomas Dickey ...

their issues and discussions are very useful

Wildcard

07:39

@cuonglm Awesome!

@cuonglm Not surprised at all.

:)

I've made it a habit for a long time now to check POSIX specs before I check man pages.

cuonglm

yep, mee too :+1:

Wildcard

Well, I have to go now, but I really appreciate you taking the time. :) Thanks!

cuonglm

No problem :)

Transcript for

Discussion between Wildcard and cuonglm