Re: Stop printing when non-comment lines are reached

[Greg Wooledge]

On Wed, Feb 01, 2023 at 03:54:51PM +0100, Hans Lonsdale wrote:
> I am printing between sections of the following form
> 
> ---------
> ## FAML [ASMB] keyword,keyword  
> 
> ## Some text
> 
> ## END OF FAML [ASMB]
> ---------
> 
> I have encountered a problem that occurs when "## END OF FAML [ASMB]" is not 
> reached. 
> I want to stop as soon as lines not starting with comment characters "##" are 
> encountered.

Oh, now there's additional text on the starting line?  And those ##
characters are actually part of the file?  Hrmph.

I should know from experience that the problem is just going to keep
getting harder and harder and harder each time I propose an answer,
and then the OP says "No, that's not right because..." but it's still
frustrating.

The goal here is to AVOID doing stupid regular expression tricks, because
the strings you're proposing as section headers are just that -- strings.
They're not regexes.  So, we don't want to do regex matching on them.  If
we did, then we would have to convert the strings to regexes first
(inserting a boatload of backslashes in front of any characters on a
certian list), and that's just painful.

Anyway, we haven't reached that tipping point yet.  It can still be
done using string operations on strings.  Here's the next iteration.
I'm sure you're going to retort with yet another reason why this won't
work (maybe the number of # characters is meant to be variable or
something)....

unicorn:~$ cat foo
#!/bin/sh
faml="FM"
asmb="TOBIN"
exec awk -v marker="$faml [$asmb]" '
  BEGIN                         {mark=0}
  ! /^##/                       {exit}
  index($0, "## " marker) == 1  {mark=1}
  mark                          {print}
  $0 == "## END OF " marker     {exit}
' "$@"

unicorn:~$ cat bar
## leading junk
## FM [TOBIN] keyword,keyword
## Some text
## Like this?
## NOT THE END OF FM [TOBIN]
## Still going!
don't print this

unicorn:~$ ./foo bar
## FM [TOBIN] keyword,keyword
## Some text
## Like this?
## NOT THE END OF FM [TOBIN]
## Still going!

unicorn:~$ cat baz
## leading junk
## FM [TOBIN] keyword,keyword
## Some text
## Like this?
## END OF FM [TOBIN]
## Still going!
don't print this

unicorn:~$ ./foo baz
## FM [TOBIN] keyword,keyword
## Some text
## Like this?
## END OF FM [TOBIN]