Break down JSON string in simple perl or simple unix? - objective-c

Question

ok so i have have this
{"status":0,"id":"7aceb216d02ecdca7ceffadcadea8950-1","hypotheses":[{"utterance":"hello how are you","confidence":0.96311796}]}
and at the moment i'm using this shell command to decode it to get the string i need,
echo $x | grep -Po '"utterance":.*?[^\\]"' | sed -e s/://g -e s/utterance//g -e 's/"//g'
but this only works when you have a grep compiled with perl and plus the script i use to get that JSON string is written in perl, so is there any way i can do this same decoding in a simple perl script or a simpler unix command, or better yet, c or objective-c?
the script i'm using to get the json is here, http://pastebin.com/jBGzJbMk and if you want a file to use then download http://trevorrudolph.com/a.flac

Answer 1

How about:
perl -MJSON -nE 'say decode_json($_)->{hypotheses}[0]{utterance}'
in script form:
use JSON;
while (<>) {
print decode_json($_)->{hypotheses}[0]{utterance}, "\n"
}

Answer 2

Well, I'm not sure if I can deduce what you are after correctly, but this is a way to decode that JSON string in perl.
Of course, you'll need to know the data structure in order to get the data you need. The line that prints the "utterance" string is commented out in the code below.
use strict;
use warnings;
use Data::Dumper;
use JSON;
my $json = decode_json
q#{"status":0,"id":"7aceb216d02ecdca7ceffadcadea8950-1","hypotheses":[{"utterance":"hello how are you","confidence":0.96311796}]}#;
#print $json->{'hypotheses'}[0]{'utterance'};
print Dumper $json;
Output:
$VAR1 = {
'status' => 0,
'hypotheses' => [
{
'utterance' => 'hello how are you',
'confidence' => '0.96311796'
}
],
'id' => '7aceb216d02ecdca7ceffadcadea8950-1'
};
Quick hack:
while (<>) {
say for /"utterance":"?(.*?)(?<!\\)"/;
}
Or as a one-liner:
perl -lnwe 'print for /"utterance":"(.+?)(?<!\\)"/g' inputfile.txt
The one-liner is troublesome if you happen to be using Windows, since " is interpreted by the shell.
Quick hack#2:
This will hopefully go through any hash structure and find keys.
my $json = decode_json $str;
say find_key($json, 'utterance');
sub find_key {
my ($ref, $find) = #_;
if (ref $ref) {
if (ref $ref eq 'HASH' and defined $ref->{$find}) {
return $ref->{$find};
} else {
for (values $ref) {
my $found = find_key($_, $find);
if (defined $found) {
return $found;
}
}
}
}
return;
}

Answer 3

Based on the naming, it's possible to have multiple hypotheses. The prints the utterance of each hypothesis:
echo '{"status":0,"id":"7aceb216d02ecdca7ceffadcadea8950-1","hypotheses":[{"utterance":"hello how are you","confidence":0.96311796}]}' | \
perl -MJSON::XS -n000E'
say $_->{utterance}
for #{ JSON::XS->new->decode($_)->{hypotheses} }'
Or as a script:
use feature qw( say );
use JSON::XS;
my $json = '{"status":0,"id":"7aceb216d02ecdca7ceffadcadea8950-1","hypotheses":[{"utterance":"hello how are you","confidence":0.96311796}]}';
say $_->{utterance}
for #{ JSON::XS->new->decode($json)->{hypotheses} };

Answer 4

If you don't want to use any modules from CPAN and try a regex instead there are multiple variants you can try:
# JSON is on a single line:
$json = '{"other":"stuff","hypo":[{"utterance":"hi, this is \"bob\"","moo":0}]}';
# RegEx with negative look behind:
# Match everything up to a double quote without a Backslash in front of it
print "$1\n" if ($json =~ m/"utterance":"(.*?)(?<!\\)"/)
This regex works if there is only one utterance. It doesn't matter what else is in the string around it, since it only searches for the double quoted string following the utterance key.
For a more robust version you could add whitespace where necessary/possible and make the . in the RegEx match newlines: m/"utterance"\s*:\s*"(.*?)(?<!\\)"/s
If you have multiple entries for the utterance confidence hash/object, changing case and weird formatting of the JSON string try this:
# weird JSON:
$json = <<'EOJSON';
{
"status":0,
"id":"an ID",
"hypotheses":[
{
"UtTeraNcE":"hello my name is \"Bob\".",
"confidence":0.0
},
{
'utterance' : 'how are you?',
"confidence":0.1
},
{
"utterance"
: "
thought
so!
",
"confidence" : 0.9
}
]
}
EOJSON
# RegEx with alternatives:
print "$1\n" while ( $json =~ m/["']utterance["']\s*:\s*["'](([^\\"']|\\.)*)["']/gis);
The main part of this RegEx is "(([^\\"]|\\.)*)". Description in detail as extended regex:
/
["'] # opening quotes
( # start capturing parentheses for $1
( # start of grouping alternatives
[^\\"'] # anything that's not a backslash or a quote
| # or
\\. # a backslash followed by anything
) # end of grouping
* # in any quantity
) # end capturing parentheses
["'] # closing quotes
/xgs
If you have many data sets and speed is a concern you can add the o modifier to the regex and use character classes instead of the i modifier. You can suppress the capturing of the alternatives to $2 with clustering parenthesis (?:pattern). Then you get this final result:
m/["'][uU][tT][tT][eE][rR][aA][nN][cC][eE]["']\s*:\s*["']((?:[^\\"']|\\.)*)["']/gos
Yes, sometimes perl looks like a big explosion in a bracket factory ;-)

Answer 5

Just stubmled upon another nice method of doing this, i finaly found how to acsess the Mac OS X JavaScript engine form commandline, heres the script,
alias jsc='/System/Library/Frameworks/JavaScriptCore.framework/Versions/A/Resources/jsc'
x='{"status":0,"id":"7aceb216d02ecdca7ceffadcadea8950-1","hypotheses":[{"utterance":"hello how are you","confidence":0.96311796}]}'
jsc -e "print(${x}['hypotheses'][0]['utterance'])"

Answer 6

Ugh, yes i came up with another answer, im strudying python and it reads arrays in both its python format and the same format as a json so, i jsut made this one liner when your variable is x
python -c "print ${x}['hypotheses'][0]['utterance']"

Answer 7

figured it out for unix but would love to see your perl and c, objective-c answers...
echo $X | sed -e 's/.*utterance//' -e 's/confidence.*//' -e s/://g -e 's/"//g' -e 's/,//g'
:D
shorter copy of the same sed:
echo $X | sed -e 's/.*utterance//;s/confidence.*//;s/://g;s/"//g;s/,//g'