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Homework and Emergencies Emergency UNIX and Linux Support Grep expression between double quotes
# 22  
Old 12-24-2009
@Radoulov:
beautiful solution!!

I can not figure out why it skips lines that begin with http:// (without surrounding double quotes) somehow putting a caret in front of that fixes it but I can't figure out why. The only flaw I could find is when the first line starts with http://

Code:
$ printf 'http://www bla bla "http://xxx" http://yyy\nhttp://zzz\n' |awk -v  RS=\" '/^http/&&$0=RS$0RS'
"http://www bla bla "
"http://xxx"

Quote:
Originally Posted by aaiaz
Scrutinizer it is not working:-
Strange:
Code:
$ echo '"http://a.b.c" blablabla "http://b.b.f"'|sed 's|\"http://[^\"]*\"|&\n|g' | sed -n 's|.*\("http://[^"]*"\).*|\1|p'
"http://a.b.c"
"http://b.b.f"

perhaps you have to use xpg4 sed ?
Last edited by Scrutinizer; 12-24-2009 at 08:31 AM..
# 23  
Old 12-24-2009
Quote:
I can not figure out why it skips lines that begin with http:// (without surrounding double quotes) somehow putting a caret in front of that fixes that but I can't figure out why
That's correct, as you correctly point out, we need the ^ to match only the occurrences between double quotes: RS is defined as ", so, except for the first line, we get the correct output.

Or you're asking a different thing?

If I'm not missing something again, this should fix the issue with the first line:

Code:
awk '/^["]*http:/&&$0=RS$0RS' RS=\"

Last edited by radoulov; 12-24-2009 at 08:44 AM.. Reason: English ...
# 24  
Old 12-24-2009
Code:
printf 'http://www bla bla "http://xxx" http://yyy\nhttp://zzz\n' | awk '/^["]*http:/&&$0=RS$0RS' RS=\"

It doesn't fix it. It is nitpicking obviously but it is interesting to understand why:

What I meant earlier is if you just look at what the RS does:
Code:
$ printf 'http://www bla bla "http://xxx" http://yyy\nhttp://zzz\n' | awk 1 RS=\"
http://www bla bla
http://xxx
 http://yyy
http://zzz

Then why is using /^http:/ skipping http://zzz ?

---------- Post updated at 13:53 ---------- Previous update was at 13:45 ----------

I found my own answer:
Code:
$ printf 'http://www bla bla "http://xxx" http://yyy\nhttp://zzz\n' | awk NR==3 RS=\"
 http://yyy
http://zzz

up till now I thought awk was working on a line basis but it appears to be working on a record basis, it is just that the default record separator coincides with a newline. Great...
# 25  
Old 12-24-2009
Quote:
It doesn't fix it
Sure, sorry Smilie

Another shot:

Code:
awk '(NR==1&&/^"http:/||NR>1&&/^http:/)&&$0=RS$0RS' RS=\"

or (less efficient):

Code:
awk '$0~"^"(NR==1?"\"":x "http:")&&$0=RS$0RS' RS=\"

Quote:
Then why is using /^http:/ skipping http://zzz ?
Because in that case http://zzz is not at the beginning of the line.

---------- Post updated at 02:03 PM ---------- Previous update was at 01:57 PM ----------
Quote:
up till now I thought awk was working on a line basis but it appears to be working on a record basis, it is just that the default record separator coincides with a newline
To be precise, in this case, as far as the output is concerned, it's the default output record separator that matters.
Of course, there is even more (even Perl does not have this one), in GNU AWK the RS could be a regexp (see also the powerful RT built-in variable),
Last edited by radoulov; 12-24-2009 at 09:13 AM..
# 26  
Old 12-24-2009
Quote:
Originally Posted by radoulov
To be precise, in this case, as far as the output is concerned, it's the default output record separator that matters.
Are you sure?
Code:
$ printf 'http://www bla bla "http://xxx" http://yyy\nhttp://zzz\n' | awk NR==3 RS=\" ORS=""
 http://yyy
http://zzz

# 27  
Old 12-24-2009
Quote:
Originally Posted by Scrutinizer
Are you sure?
Code:
$ printf 'http://www bla bla "http://xxx" http://yyy\nhttp://zzz\n' | awk NR==3 RS=\" ORS=""
 http://yyy
http://zzz

Yes,
I said: as far as the output is concerned.
I mean:

Code:
% printf 'http://www bla bla "http://xxx" http://yyy\nhttp://zzz\n' | 
  awk NR==3 RS=\" ORS=
 http://yyy
http://zzz

vs.

Code:
$ printf 'http://www bla bla "http://xxx" http://yyy\nhttp://zzz\n' | awk NR==3 RS=\" OR=\"
 http://yyy
http://zzz
"$

Re-reading your statement:

Quote:
[...]but it appears to be working on a record basis, it is just that the default record separator coincides with a newline
... I realize that you meant something different (and far more obvious Smilie).
# 28  
Old 12-24-2009
Quote:
Originally Posted by radoulov
Re-reading your statement:

... I realize that you meant something different (and far more obvious Smilie).
I agree it is obvious and I realize I knew that already, but sometimes in a different context it takes a renewed realization to really realize something if that make any sense... Oh well Smilie

---------- Post updated at 14:31 ---------- Previous update was at 14:24 ----------
Quote:
Originally Posted by radoulov
Sure, sorry

Another shot:

Code:
awk '(NR==1&&/^"http:/||NR>1&&/^http:/)&&$0=RS$0RS' RS=\"

or (less efficient):

Code:
awk '$0~"^"(NR==1?"\"":x "http:")&&$0=RS$0RS' RS=\"

B
Yes, both work fine...
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