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Help with awk

 
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# 1  
Old 02-04-2012
Help with awk
Hi, I'm trying to parse a file that looks like this to create an output file based on the first 3 characters
Code:
FL1ABC 
LEX123 
FL1DDD 
LEX888
LEXTHE 
FL1EEE 
FL1FFF 
LEX555

The file will need to have the LEX records appended to each of
the FL1 records above it like this:
Code:
FL1ABCLEX123 
FL1DDDLEX888
FL1DDDLEXTHE 
FL1EEE 
FL1FFFLEX555

Currently i am using
Code:
awk ' 
/^FL1/ { key[++k] = $0; print > "list"; next} 
/^LEX/ { lex[k]   = $0 } 
END    { for (i=1; i<=k; i++) print key[i] lex[i] } 
'  filename

This is giving me
Code:
FL1ABCLEX123 
FL1DDDLEXTHE 
FL1EEE 
FL1FFFLEX555

i.e FL1DDDLEX888 record is getting missed out. Thanks in advance for any help you could provide

Akshay
Last edited by Franklin52; 02-07-2012 at 08:54 AM.. Reason: Please use code tags for code and data samples, thank you
# 2  
Old 02-04-2012
Hi akshay01987,

One way:
Code:
$ cat infile
FL1ABC
LEX123
FL1DDD
LEX888
LEXTHE
FL1EEE
FL1FFF
LEX555 
$ cat script.awk
## When line begins with 'FL1' ...
$0 ~ /^FL1/ {
        ## If previous line also began with 'FL1', flag 'prev_fl1' will
        ## be active, so print it because its value will be overwritten.
        if ( prev_fl1 ) {
                print fl1
        }
        ## Save current 'FL1' register.
        fl1 = $0
        ## Set flag to indicate that last processed line began with 'FL1'
        prev_fl1 = 1
        ## Process next line.
        next
}

## For all other lines...
{
        ## Print previous value of 'FL1' register with current one appended.
        printf "%s%s\n", fl1, $0
        ## Unset variable.
        prev_fl1 = 0
}

END {
        if ( prev_fl1 ) {
                print fl1
        }
}

$ awk -f script.awk infile
FL1ABCLEX123
FL1DDDLEX888
FL1DDDLEXTHE
FL1EEE
FL1FFFLEX555

Regards,
Birei
This User Gave Thanks to birei For This Post:
akshay01987
# 3  
Old 02-05-2012
Thanks a lot bretei

But my requirement is that only LEX records must be appended to FL1 records. Rest all should be ignored and also if there are two or more LEX records they must be appended with previous FL1 record.

Input File
Code:
FL1ABC 
LEX123 
FL1DDD 
LEX888
LEXTHE 
XXX345
FL1EEE 
FL1FFF 
LEX555
RTY567


Then the output should be like
Code:
FL1ABCLEX123 
FL1DDDLEX888
FL1DDDLEXTHE 
FL1EEE 
FL1FFFLEX555

Last edited by Franklin52; 02-07-2012 at 08:55 AM.. Reason: Please use code tags for code and data samples, thank you
# 4  
Old 02-05-2012
Code:
nawk '/^FL1/{x=$0;printf (f?RS:z) x;f++}/^LEX/{print (f?z:x) $0;f=z}' yourfile

This User Gave Thanks to ctsgnb For This Post:
akshay01987
# 5  
Old 02-05-2012
HI ctsgnb

I really thank for the effort u have taken for this i would really appreciate if you could just explain to me wat the code does.

I m a novice in this awk arena Smilie
# 6  
Old 02-05-2012
/^FL1/if the scanned line begins with FL1...
{x=$0store the line in variable x
f?RS:zif f is true (f is not empty AND f is not equal to 0) then take the value of the Record Separator, whose default value is «newline » (character \n) otherwise take the value of z (which actually is just a variable that has not been set so that is empty)
(f?RS:z) xThis is the concatenation of the value taken by the previously described (...) expression with the content of variable x
printf (f?RS:z) xthis display the previously described concatenation but keep on the same line
f++}this is same as f=f+1 (i set the flag to mark that a new FL1 line has just be scanned & printed and that no corresponding LEX line have been printed so far)
/^LEX/if the scanned line start with LEX...
{print (f?z:x) $0if f flag is set we can just print the concatenation of z and $0 (z is actually a variable that has never been set so it is empty) otherwise we need to concatenate the last found FL1 line (which was sored in variable x) to our current LEX line ($0)
f=z}'if we are in LEX line, we must reset the f flag since at least 1 LEX line has been found for the last FL1 line.
---------- Post updated at 10:09 PM ---------- Previous update was at 09:56 PM ----------

You can enhance my code with :
Code:
nawk '/^FL1/{x=$0;printf (f?RS:z) x;f++}/^LEX/{print (f?z:x) $0;f=z}END{printf f?RS:z}' inputfile



Just to ensur that the last line is displayed properly
(in the previous version, if the last line was a FL1 line, a missing "newline" character needed to be displayed to have a better output
This User Gave Thanks to ctsgnb For This Post:
akshay01987
# 7  
Old 02-07-2012
Thanks a lot ctsgnb ; It works like a charm Smilie

---------- Post updated at 04:10 AM ---------- Previous update was at 04:07 AM ----------

Could you let me know on which UNix resources i will have to refer to if i need to scale up in this particular arena
 
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