Nifi Expression language: append or prepend the attribute with string "$$$"

[#1]

I have requirement where I need to append and prepend the attribute with "$$$". how ever, Nifi expression language is appending or prepending with "\$"

For example: if attribute named "myattr" value is "This is Test"

when I do ${myattr:prepend('$$$'):append('$$$')}

I am expecting "$$$This is Test$$$"

but the output is "\$This is Test\$"

Is there any way to append or prepend the attribute with "$$$"

[#2 · Accepted solution]

@Anil Reddy

use 9$ instead of 3$

${myattr:prepend('$$$$$$$$$'):append('$$$$$$$$$')}

in expression language if you use 3$ are results as 1$ so we need to use 9$ if you want 3$ sign to be added to the attribute value.

Input:-
"myattr" value is "This is Test"

expression:-
${myattr:prepend('$$$$$$$$$'):append('$$$$$$$$$')}

Output:-
$$$This is Test$$$

[#3 · Accepted solution]

@Anil Reddy

use 9$ instead of 3$

${myattr:prepend('$$$$$$$$$'):append('$$$$$$$$$')}

in expression language if you use 3$ are results as 1$ so we need to use 9$ if you want 3$ sign to be added to the attribute value.

Input:-
"myattr" value is "This is Test"

expression:-
${myattr:prepend('$$$$$$$$$'):append('$$$$$$$$$')}

Output:-
$$$This is Test$$$

[#4]

what might be the reason for the extra character '\' ?

[#5]

it seems like replaceText processor is replacing '$$$$$*' in the content to '\$' while replacing the flow file content!

seems like actual issue is I have an attribute namely "myattr"

when myattr is "$$This is test$$", if I replace the flowfile content with myattr, the content in the flowfile is "\$this is test\$"

[#6]

Thanks, prepend worked for me, I needed to add a comma before a value.

[#7 · Accepted solution]

@SS_Jin 
Another option is to use the NiFi expression Language (NEL) function "literal()}" in the NEL statement:

${myattr:append(${literal('$$$')}):prepend(${literal('$$$')})}

This removes the need to you are using the correct number of "$" to escape $ in the NEL.

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Thank you,
Matt

[#8]

That's perfect !