[SOLVED] Getting JSON value from JSON String using Shell Script

Issue

I have this JSON String:

{"name":"http://someUrl/ws/someId","id":"someId"}

I just want to get value for "id" key and store it in some variable. I succesfully tried using jq. But due to some constraints, I need to achieve this just by using grep and string matching.

I tried this so far: grep -Po '"id":.*?[^\\]"'; But that is giving "id":"ws-4c906698-03a2-49c3-8b3e-dea829c7fdbe" as output. I just need the id value. Please help

Solution

With a PCRE regex, you may use lookarounds. Thus, you need to put "id":" into the positive lookbehind construct, and then match 1 or more chars other than ":

grep -Po '(?<="id":")[^"]+'

where

• (?<="id":") - requires a "id":" to appear immediately to the left of the current position (but the matched text is not added to the match value) and
• [^"]+ - matches and adds to the match 1 or more chars other than ".

To get the values with escaped quotes:

grep -Po '(?<="id":")[^"\\]*(?:\\.[^"\\]*)*'

Here, (?<="id":") will still match the position right after "id":" and then the following will get matched:

• [^"\\]* - zero or more chars other than " and \
• (?:\\.[^"\\]*)* - zero or more consequent sequences of:
  • \\. - a \ and any char (any escape sequence)
  • [^"\\]* - zero or more chars other than " and \

Answered By - Wiktor Stribiżew