How to add an element to json file in perl [closed] - json

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To change the md5 checksum of a json file, I am using the following filter in my httpd.conf:
ExtFilterDefine jsonfilter mode=output intype=application/json cmd="/usr/bin/perl -pe 'END { unless (-f q{/tmp/md5_filter.tmp}) { print qq(\\n\,\"STRING\"\: \") . time() . qq(\x0D\"\\n) }'"
But after the filter run, I receive an error, probally because the new string / timestamp get added after the last bracket } and leads to an unvalid json format:
SyntaxError: JSON.parse: unexpected non-whitespace character after JSON data at line 224 column 2 of the JSON data
Does someone know how to get this run correctly? Just to be sure: I just want to change the output of the file, before it gets response to the client browser. I don't want to change the original file itself. This should be untouched.

Answer 1

probally because the new string / timestamp get added after the last bracket } and leads to an unvalid json format
I don't know any details of the environment that you're working in, but I suspect that your suspicion is correct here.
You could try to fix your string-manipulating solution (perhaps by working out when you're processing the final line of the input and then printing your addition before printing the closing brace. But the best solution is to gather the input into a single string and then process it using a JSON parser.
Something like this (untested):
perl -MJSON -ne '$json .= $_; END { my $data = decode_json($json); $data->{STRING} = time; print encode_json($data);'
Update: To explain the various parts of my code.
-MJSON - loads the JSON module
-ne - n iterates over the input (putting each line, in turn, into $_); e executes code from the command line
$json .= $_ - this is run for every line of the input. It just takes each line and gathers them all together in a variable called $json
END { ... } - this block of code is only run once - after the input has all been read
my $data = decode_json($json) - takes the JSON text string (now stored in $json) and decodes it into a Perl data structure. That data structure is stored in $data
$data->{STRING} = time - adds another key/value pair to the data structure
print encode_json($data) - encodes the altered data structure back into a JSON string and prints that string to STDOUT