GNU bug report logs - #75197
[Feature Request] Support 'grep -A' without number to show all lines after match

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From: jackson <at> fastmail.fm
To: "Paul Eggert" <eggert <at> cs.ucla.edu>, KMRH <kmrh47 <at> proton.me>
Cc: 75197 <at> debbugs.gnu.org
Subject: bug#75197: [Feature Request] Support 'grep -A' without number to show all lines after match
Date: Mon, 30 Dec 2024 14:14:35 -0600

Or, for us old farts who have been using 'sed' for a half century, if I wanted to print the lines in a file starting with the line matching a certain pattern, through the remaining lines of the file, I'd use:

  sed -n '/pattern/,$/p' < file

Then I wouldn't have to worry whether or not the 'grep' command I was using would lose it's lunch trying to parse '9999999999999999999999', though, granted, every executable 'grep' binary I happen to have on my disk, a couple dozen of them going back over 20 years, all handle the forty-nine 9's I just tested, HOWEVER the busybox 0.51 grep source code circa 2001 I have at hand will fail if strtoul of  the numeric argument to "-A" overflows, returning ULONG_MAX with errno of ERANGE, and likely some older variants of grep would also fail, _and_

I wouldn't have to worry that my 'magic' number wasn't big enough for every ordinary, already written to disk, file that I might be reading, _and_

I could run this off a pipe that never ended with a normal closure of the input stream that would have sent an EOF to input stream of 'sed', but only ended with a signal or hardware stoppage, without worrying that I had not put enough nine's (9) in my number, _and_

I wouldn't have readers of that code wondering what that strange number was ... though, granted, I would have them doing 'man sed' ... about time in my book.

But, yes, as Paul Eggert notes, command line parsing of 'grep -A 123'  would be ambiguous.  Is "123"  a filename, or a parameter to the "-A" argument?

-- 
Paul Jackson
jackson <at> fastmail.fm

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