jp

jp

jp is a program that can be used to grok json at the command line via path expressions. Here it is used as a demo for build process.

Dockerfile and Makefile are used to illustrate docker build and deployment examples.

Usage:

As a pretty printer.

cat file.json | jp

You can use print to print a specific node in the JSON. The docker inspect command outputs JSON which can be piped to jp which then can select a particular path and node in the JSON. The - before print indicates that JSON input is stdin.

$ docker inspect a6a2 | jp - print /[0]/Config/Env
["PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"]

You can save the JSON output and parse conditionally. The following prints memory capacity of the system.

$ lshw -json > /tmp/x
$ jp /tmp/x if  'children[0]/children[0]/id == memory' print /children[0]/children[0]/size
3.3663483904e+10

You can use foreach to print elements of an Array:

$ jp /tmp/x foreach  'children[0]/children' print |wc -l
3

The following lists out array at children[0]/children[]. Then each line is piped again to another jp to check for CPU 0 capabilities and capacity.

$ jp /tmp/x foreach  'children[0]/children' print | \
while read line; do echo $line | \
    jp - if 'businfo == cpu@0' list /capabilities/vmx /capacity  ;done 
true 3.400132e+09 

You can run it in server mode which will serve at a given port.

jp -port 8080 -server

Connect web browser to http://localhost:8080.

jy

The directory jy contains a program that can convert YAML to JSON and back.