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File Reading for a certain string and echo the line before

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Top Forums Shell Programming and Scripting File Reading for a certain string and echo the line before
# 8  
Old 03-09-2012
Quote:
Originally Posted by alister
Hi, ctsgnb:

Works fine for me with a BSD sed. Also, the script should be POSIX-compliant.

If you figure out why it fails on your implementation, I'd be interested to know; I'm not familiar with your system's userland.

Regards,
Alister

Some older seds don't play well without newlines. I was able to get it to work by inserting newlines.



Code:
sed -n '/Failed/{
x;
//!p;
x;
}; 
h' file


I was surprised that the 'one liner' didn't work with the version in xpg4 either.
This User Gave Thanks to agama For This Post:
alister
# 9  
Old 03-10-2012
Quote:
Originally Posted by alister
Just because the problem has been solved does not mean that the fun must come to an end. Smilie
Code:
sed -n '/Failed/{x;//!p;x;}; h' infile

Regards,
Alister
Ingenious and fun indeed!

Quote:
Originally Posted by ctsgnb
@alister

I tried your code (on a SunOS 5.10 machine), it didn't work [..]
Were you using /usr/xpg4/bin/sed ?
Last edited by Scrutinizer; 03-10-2012 at 06:02 AM..
# 10  
Old 03-12-2012
@alister :

Hi

Just to give a feedback : i gave a try inserting new line (as suggested by agama) , i confirm your code works fine that way

Code:
# sed -n '/Failed/{x
> //!p
> x
> }
> h' my
call ttcacheautorefreshstatsget('CGOWNER','CG_CLIENT_PLAN');
#

@Scruti

I also gave a try with /usr/xpg4/bin/sed : it doesn't work one line ... it looks it still need to be run in several lines :

Code:
# /usr/xpg4/bin/sed -n '/Failed/{x;//!p;x;}; h' my










#

Code:
# # /usr/xpg4/bin/sed -n '/Failed/{x
> //# !p
> x
> }
> h' my
call ttcacheautorefreshstatsget('CGOWNER','CG_CLIENT_PLAN');
#

Last edited by ctsgnb; 03-12-2012 at 05:51 AM..
These 2 Users Gave Thanks to ctsgnb For This Post:
alister Scrutinizer
# 11  
Old 03-12-2012
Thanks for the feedback. I looked up the latest POSIX specification and I think indeed newlines should be used instead of semicolons...
Quote:
Historically, the sed ! and } editing commands did not permit multiple commands on a single line using a <semicolon> as a command delimiter. Implementations are permitted, but not required, to support this extension.
sed: rationale

There is also this passage:
Quote:
Command verbs other than {, a, b, c, i, r, t, w, :, and # can be followed by a <semicolon>, optional <blank> characters, and another command verb[..]
Editing Commands in sed
Last edited by Scrutinizer; 03-12-2012 at 06:16 AM..
These 2 Users Gave Thanks to Scrutinizer For This Post:
alister ctsgnb
# 12  
Old 03-12-2012
Although I already knew that those commands listed in your second quote should not be delimited by a semicolon, it's news to me that POSIX does not require it for the others.

Thank you very much for the POSIX enlightenment, Scrutinizer.

And thanks for reporting back, ctsgnb.

Regards,
Alister
# 13  
Old 03-12-2012
@Scruti & Alister :

Just to validate that this is the handling of the semicolon after the {} clause that caused the error, i gave a last shot :

see :

Code:
# /usr/xpg4/bin/sed -n '/Failed/{x;//!p;x;};h' my










#

Code:
# /usr/xpg4/bin/sed -n '/Failed/{x;//!p;x;}
> h' my
call ttcacheautorefreshstatsget('CGOWNER','CG_CLIENT_PLAN');
#

... worked !
These 3 Users Gave Thanks to ctsgnb For This Post:
agama alister Scrutinizer
# 14  
Old 03-12-2012
Nice job narrowing it down, ctsgnb.

Regards,
Alister
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