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awk - find first occurence and replace it

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# 1  
Old 03-04-2015
Power awk - find first occurence and replace it
Hello,

I have a requirement to replace the whole string with first occurence of value of a key-value pair.

I have to do this inside awk, as the data I need to work is inside an awk loop.

value of my variable(say LogText) looks like:
LogText=
Code:
date=04Mar message=hello1 name=caq message=hello2 address=abc message=hello3 city=xyz

I need to extract value of first occurence of message (ie.., hello1) into a new variable

I am using the function gensub inside awk to do this. I have tried:

Code:
awk -v LogText="$Log_Text" '{ 
MSG_VALUE=gensub(/^.*message=([A-Za-z0-9]+).*$/,"\\1", 1,LogText); 
print MSG_VALUE
}'

But this is always storing the value of last occurence of message(=hello3) into MSG_VALUE.

I have also tried negative lookaback:
Code:
MSG_VALUE=gensub(/^.*(?!<message).*message=([A-Za-z0-9]+).*$/,"\\1", 1,LogText);

Maybe something wrong here, it fails to match any part of string.

Could anyone help?
I've spent quite a few hours to figure this out and searching on the web before posting here.


Thanks,
CaQ
# 2  
Old 03-04-2015
Just add an exit at the end, so it will exit after the first match
Code:
awk -v LogText="$Log_Text" '{  
MSG_VALUE=gensub(/^.*message=([A-Za-z0-9]+).*$/,"\\1", 1,LogText)  
print MSG_VALUE
exit
  }'

# 3  
Old 03-04-2015
Try
Code:
 awk -vL="$LogText" 'BEGIN {sub(/^[^ ]* message=/, "", L); sub (/ .*$/, "", L); print L}'
hello1

This User Gave Thanks to RudiC For This Post:
cool.aquarian
# 4  
Old 03-04-2015
Quote:
Originally Posted by RudiC
Try
Code:
 awk -vL="$LogText" 'BEGIN {sub(/^[^ ]* message=/, "", L); sub (/ .*$/, "", L); print L}'
hello1

Thanks for this. It worked for me.
I have similar need for another use case.
Here, the variable LogText contains a JSON(which can be multiline), and I want to extract the first occurence same way:

LogText:
Code:
{
    "date" : "04-Mar",
    "name" : "john doe",
    "message" : "hello1",
    "role" : "dev",
    "message" : "hello2",
    "dept" : "chemistry",
    "message" : "hello3"
}

I am trying to obtain the first value of message (hello1) from this
Any clue on this? Smilie
# 5  
Old 03-05-2015
Try
Code:
awk -vL="$L" 'BEGIN {n=split (L, T, "\n"); for (i=1; i<=n; i++) if (T[i] ~ /message/) {split (T[i], K, "\""); print K[4]; break}}'
hello1

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