Check out the jc Python package documentation for developers

Try the jc web demo

JC is now available as an Ansible filter plugin in the community.general collection. See this blog post for an example.

JC

JSON Convert

jc JSONifies the output of many CLI tools, file-types, and common strings for easier parsing in scripts. See the Parsers section for supported commands, file-types, and strings.

dig example.com | jc --dig

[{"id":38052,"opcode":"QUERY","status":"NOERROR","flags":["qr","rd","ra"],
"query_num":1,"answer_num":1,"authority_num":0,"additional_num":1,
"opt_pseudosection":{"edns":{"version":0,"flags":[],"udp":4096}},"question":
{"name":"example.com.","class":"IN","type":"A"},"answer":[{"name":
"example.com.","class":"IN","type":"A","ttl":39049,"data":"93.184.216.34"}],
"query_time":49,"server":"2600:1700:bab0:d40::1#53(2600:1700:bab0:d40::1)",
"when":"Fri Apr 16 16:09:00 PDT 2021","rcvd":56,"when_epoch":1618614540,
"when_epoch_utc":null}]

This allows further command-line processing of output with tools like jq or jello by piping commands:

$ dig example.com | jc --dig | jq -r '.[].answer[].data'
93.184.216.34

or using the alternative "magic" syntax:

$ jc dig example.com | jq -r '.[].answer[].data'
93.184.216.34

jc can also be used as a python library. In this case the output will be a python dictionary, a list of dictionaries, or even a lazy iterable of dictionaries instead of JSON:

>>> import subprocess
>>> import jc
>>>
>>> cmd_output = subprocess.check_output(['dig', 'example.com'], text=True)
>>> data = jc.parse('dig', cmd_output)
>>>
>>> data[0]['answer']
[{'name': 'example.com.', 'class': 'IN', 'type': 'A', 'ttl': 29658, 'data':
'93.184.216.34'}]

For jc Python package documentation, use help('jc'), help('jc.lib'), or see the online documentation.

Two representations of the data are available. The default representation uses a strict schema per parser and converts known numbers to int/float JSON values. Certain known values of None are converted to JSON null, known boolean values are converted, and, in some cases, additional semantic context fields are added.

To access the raw, pre-processed JSON, use the -r cli option or the raw=True function parameter in parse().

Schemas for each parser can be found at the documentation link beside each Parser below.

Release notes can be found here.

Why Would Anyone Do This!?

For more information on the motivations for this project, please see my blog post on Bringing the Unix Philosophy to the 21st Century and my interview with Console.

See also:

• libxo on FreeBSD
• powershell
• blog: linux apps should have a json flag
• Hacker News discussion
• Reddit discussion

Use Cases:

• Bash scripting
• Ansible command output parsing
• Saltstack command output parsing
• Nornir command output parsing
• FortiSOAR command output parsing

Installation

There are several ways to get jc. You can install via pip, OS package repositories, or by downloading the correct binary for your architecture and running it anywhere on your filesystem.

Pip (macOS, linux, unix, Windows)

pip3 install jc

OS Package Repositories

For more OS Packages, see https://repology.org/project/jc/versions.

Binaries

For precompiled binaries, see Releases on Github.

Usage

jc accepts piped input from STDIN and outputs a JSON representation of the previous command's output to STDOUT.

COMMAND | jc PARSER [OPTIONS]

Alternatively, the "magic" syntax can be used by prepending jc to the command to be converted. Options can be passed to jc immediately before the command is given. (Note: command aliases and shell builtins are not supported)

jc [OPTIONS] COMMAND

The JSON output can be compact (default) or pretty formatted with the -p option.

Parsers

Options

Exit Codes

Any fatal errors within jc will generate an exit code of 100, otherwise the exit code will be 0. When using the "magic" syntax (e.g. jc ifconfig eth0), jc will store the exit code of the program being parsed and add it to the jc exit code. This way it is easier to determine if an error was from the parsed program or jc.

Consider the following examples using ifconfig:

Setting Custom Colors via Environment Variable

You can specify custom colors via the JC_COLORS environment variable. The JC_COLORS environment variable takes four comma separated string values in the following format:

JC_COLORS=<keyname_color>,<keyword_color>,<number_color>,<string_color>

Where colors are: black, red, green, yellow, blue, magenta, cyan, gray, brightblack, brightred, brightgreen, brightyellow, brightblue, brightmagenta, brightcyan, white, or default

For example, to set to the default colors:

JC_COLORS=blue,brightblack,magenta,green

or

JC_COLORS=default,default,default,default

Disable Colors via Environment Variable

You can set the NO_COLOR environment variable to any value to disable color output in jc. Note that using the -C option to force color output will override both the NO_COLOR environment variable and the -m option.

Streaming Parsers

Most parsers load all of the data from STDIN, parse it, then output the entire JSON document serially. There are some streaming parsers (e.g. ls-s and ping-s) that immediately start processing and outputing the data line-by-line as JSON Lines (aka NDJSON) while it is being received from STDIN. This can significantly reduce the amount of memory required to parse large amounts of command output (e.g. ls -lR /) and can sometimes process the data more quickly. Streaming parsers have slightly different behavior than standard parsers as outlined below.

Note: Streaming parsers cannot be used with the "magic" syntax

Ignoring Errors

You may want to ignore parsing errors when using streaming parsers since these may be used in long-lived processing pipelines and errors can break the pipe. To ignore parsing errors, use the -qq cli option or the ignore_exceptions=True argument with the parse() function. This will add a _jc_meta object to the JSON output with a success attribute. If success is true, then there were no issues parsing the line. If success is false, then a parsing issue was found and error and line fields will be added to include a short error description and the contents of the unparsable line, respectively:

Successfully parsed line with -qq option:

{
  "command_data": "data",
  "_jc_meta": {
    "success": true
  }
}

Unsuccessfully parsed line with -qq option:

{
  "_jc_meta": {
    "success": false,
    "error": "error message",
    "line": "original line data"
  }
}

Unbuffering Output

Most operating systems will buffer output that is being piped from process to process. The buffer is usually around 4KB. When viewing the output in the terminal the OS buffer is not engaged so output is immediately displayed on the screen. When piping multiple processes together, though, it may seem as if the output is hanging when the input data is very slow (e.g. ping):

$ ping 1.1.1.1 | jc --ping-s | jq
<slow output>

This is because the OS engages the 4KB buffer between jc and jq in this example. To display the data on the terminal in realtime, you can disable the buffer with the -u (unbuffer) cli option:

$ ping 1.1.1.1 | jc --ping-s -u | jq
{"type":"reply","pattern":null,"timestamp":null,"bytes":"64","respons...}
{"type":"reply","pattern":null,"timestamp":null,"bytes":"64","respons...}
...

Note: Unbuffered output can be slower for large data streams.

Using Streaming Parsers as Python Modules

Streaming parsers accept any iterable object and return an iterable object allowing lazy processing of the data. The input data should iterate on lines of string data. Examples of good input data are sys.stdin or str.splitlines().

To use the returned iterable object in your code, simply loop through it or use the next() builtin function:

import jc

result = jc.parse('ls_s', ls_command_output.splitlines())
for item in result:
    print(item["filename"])

Custom Parsers

Custom local parser plugins may be placed in a jc/jcparsers folder in your local "App data directory":

• Linux/unix: $HOME/.local/share/jc/jcparsers
• macOS: $HOME/Library/Application Support/jc/jcparsers
• Windows: $LOCALAPPDATA\jc\jc\jcparsers

Local parser plugins are standard python module files. Use the jc/parsers/foo.py or jc/parsers/foo_s.py (streaming) parser as a template and simply place a .py file in the jcparsers subfolder.

Local plugin filenames must be valid python module names and therefore must start with a letter and consist entirely of alphanumerics and underscores. Local plugins may override default parsers.

Note: The application data directory follows the XDG Base Directory Specification

Caveats

Locale

For best results set the locale environment variables to C or en_US.UTF-8 by modifying the LC_ALL variable:

$ LC_ALL=C date | jc --date

You can also set the locale variables individually:

$ export LANG=C
$ export LC_NUMERIC=C

On some older systems UTF-8 output will be downgraded to ASCII with \\u escape sequences if the C locale does not support UTF-8 encoding.

Timezones

Some parsers have calculated epoch timestamp fields added to the output. Unless a timestamp field name has a _utc suffix it is considered naive. (i.e. based on the local timezone of the system the jc parser was run on).

If a UTC timezone can be detected in the text of the command output, the timestamp will be timezone aware and have a _utc suffix on the key name. (e.g. epoch_utc) No other timezones are supported for aware timestamps.

Use In Other Shells

jc can be used in most any shell. Some modern shells have JSON deserialization and filtering capabilities built-in which makes using jc even more convenient.

For example, the following is possible in NGS (Next Generation Shell):

myvar = ``jc dig www.google.com``[0].answer[0].data

This runs jc, parses the output JSON, and assigs the resulting data structure to a variable in a single line of code.

For more examples of how to use jc in other shells, see this wiki page.

Compatibility

Some parsers like dig, xml, csv, etc. will work on any platform. Other parsers that convert platform-specific output will generate a warning message if they are run on an unsupported platform. To see all parser information, including compatibility, run jc -ap.

You may still use a parser on an unsupported platform - for example, you may want to parse a file with linux lsof output on an macOS or Windows laptop. In that case you can suppress the warning message with the -q cli option or the quiet=True function parameter in parse():

macOS:

cat lsof.out | jc --lsof -q

or Windows:

type lsof.out | jc --lsof -q

Tested on:

• Centos 7.7
• Ubuntu 18.04
• Ubuntu 20.04
• Fedora32
• macOS 10.11.6
• macOS 10.14.6
• NixOS
• FreeBSD12
• Windows 10
• Windows 2016 Server
• Windows 2019 Server

Contributions

Feel free to add/improve code or parsers! You can use the jc/parsers/foo.py or jc/parsers/foo_s.py (streaming) parsers as a template and submit your parser with a pull request.

Please see the Contributing Guidelines for more information.

Acknowledgments

• Local parser plugin feature contributed by Dean Serenevy
• CI automation and code optimizations by philippeitis
• ifconfig-parser module by KnightWhoSayNi
• xmltodict module by Martín Blech
• ruamel.yaml module by Anthon van der Neut
• trparse module by Luis Benitez
• Parsing code from Conor Heine adapted for some parsers
• Excellent constructive feedback from Ilya Sher

Examples

Here are some examples of jc output. For more examples, see here or the parser documentation.

arp

arp | jc --arp -p          # or:  jc -p arp

[
  {
    "address": "gateway",
    "hwtype": "ether",
    "hwaddress": "00:50:56:f7:4a:fc",
    "flags_mask": "C",
    "iface": "ens33"
  },
  {
    "address": "192.168.71.1",
    "hwtype": "ether",
    "hwaddress": "00:50:56:c0:00:08",
    "flags_mask": "C",
    "iface": "ens33"
  },
  {
    "address": "192.168.71.254",
    "hwtype": "ether",
    "hwaddress": "00:50:56:fe:7a:b4",
    "flags_mask": "C",
    "iface": "ens33"
  }
]

CSV files

cat homes.csv

"Sell", "List", "Living", "Rooms", "Beds", "Baths", "Age", "Acres", "Taxes"
142, 160, 28, 10, 5, 3,  60, 0.28,  3167
175, 180, 18,  8, 4, 1,  12, 0.43,  4033
129, 132, 13,  6, 3, 1,  41, 0.33,  1471
...

cat homes.csv | jc --csv -p

[
  {
    "Sell": "142",
    "List": "160",
    "Living": "28",
    "Rooms": "10",
    "Beds": "5",
    "Baths": "3",
    "Age": "60",
    "Acres": "0.28",
    "Taxes": "3167"
  },
  {
    "Sell": "175",
    "List": "180",
    "Living": "18",
    "Rooms": "8",
    "Beds": "4",
    "Baths": "1",
    "Age": "12",
    "Acres": "0.43",
    "Taxes": "4033"
  },
  {
    "Sell": "129",
    "List": "132",
    "Living": "13",
    "Rooms": "6",
    "Beds": "3",
    "Baths": "1",
    "Age": "41",
    "Acres": "0.33",
    "Taxes": "1471"
  }
]

/etc/hosts file

cat /etc/hosts | jc --hosts -p

[
  {
    "ip": "127.0.0.1",
    "hostname": [
      "localhost"
    ]
  },
  {
    "ip": "::1",
    "hostname": [
      "ip6-localhost",
      "ip6-loopback"
    ]
  },
  {
    "ip": "fe00::0",
    "hostname": [
      "ip6-localnet"
    ]
  }
]

ifconfig

ifconfig | jc --ifconfig -p          # or:  jc -p ifconfig

[
  {
    "name": "ens33",
    "flags": 4163,
    "state": [
      "UP",
      "BROADCAST",
      "RUNNING",
      "MULTICAST"
    ],
    "mtu": 1500,
    "ipv4_addr": "192.168.71.137",
    "ipv4_mask": "255.255.255.0",
    "ipv4_bcast": "192.168.71.255",
    "ipv6_addr": "fe80::c1cb:715d:bc3e:b8a0",
    "ipv6_mask": 64,
    "ipv6_scope": "0x20",
    "mac_addr": "00:0c:29:3b:58:0e",
    "type": "Ethernet",
    "rx_packets": 8061,
    "rx_bytes": 1514413,
    "rx_errors": 0,
    "rx_dropped": 0,
    "rx_overruns": 0,
    "rx_frame": 0,
    "tx_packets": 4502,
    "tx_bytes": 866622,
    "tx_errors": 0,
    "tx_dropped": 0,
    "tx_overruns": 0,
    "tx_carrier": 0,
    "tx_collisions": 0,
    "metric": null
  }
]

INI files

cat example.ini

[DEFAULT]
ServerAliveInterval = 45
Compression = yes
CompressionLevel = 9
ForwardX11 = yes

[bitbucket.org]
User = hg

[topsecret.server.com]
Port = 50022
ForwardX11 = no

cat example.ini | jc --ini -p

{
  "bitbucket.org": {
    "serveraliveinterval": "45",
    "compression": "yes",
    "compressionlevel": "9",
    "forwardx11": "yes",
    "user": "hg"
  },
  "topsecret.server.com": {
    "serveraliveinterval": "45",
    "compression": "yes",
    "compressionlevel": "9",
    "forwardx11": "no",
    "port": "50022"
  }
}

ls

$ ls -l /usr/bin | jc --ls -p          # or:  jc -p ls -l /usr/bin

[
  {
    "filename": "apropos",
    "link_to": "whatis",
    "flags": "lrwxrwxrwx.",
    "links": 1,
    "owner": "root",
    "group": "root",
    "size": 6,
    "date": "Aug 15 10:53"
  },
  {
    "filename": "ar",
    "flags": "-rwxr-xr-x.",
    "links": 1,
    "owner": "root",
    "group": "root",
    "size": 62744,
    "date": "Aug 8 16:14"
  },
  {
    "filename": "arch",
    "flags": "-rwxr-xr-x.",
    "links": 1,
    "owner": "root",
    "group": "root",
    "size": 33080,
    "date": "Aug 19 23:25"
  }
]

netstat

netstat -apee | jc --netstat -p          # or:  jc -p netstat -apee

[
  {
    "proto": "tcp",
    "recv_q": 0,
    "send_q": 0,
    "local_address": "localhost",
    "foreign_address": "0.0.0.0",
    "state": "LISTEN",
    "user": "systemd-resolve",
    "inode": 26958,
    "program_name": "systemd-resolve",
    "kind": "network",
    "pid": 887,
    "local_port": "domain",
    "foreign_port": "*",
    "transport_protocol": "tcp",
    "network_protocol": "ipv4"
  },
  {
    "proto": "tcp6",
    "recv_q": 0,
    "send_q": 0,
    "local_address": "[::]",
    "foreign_address": "[::]",
    "state": "LISTEN",
    "user": "root",
    "inode": 30510,
    "program_name": "sshd",
    "kind": "network",
    "pid": 1186,
    "local_port": "ssh",
    "foreign_port": "*",
    "transport_protocol": "tcp",
    "network_protocol": "ipv6"
  },
  {
    "proto": "udp",
    "recv_q": 0,
    "send_q": 0,
    "local_address": "localhost",
    "foreign_address": "0.0.0.0",
    "state": null,
    "user": "systemd-resolve",
    "inode": 26957,
    "program_name": "systemd-resolve",
    "kind": "network",
    "pid": 887,
    "local_port": "domain",
    "foreign_port": "*",
    "transport_protocol": "udp",
    "network_protocol": "ipv4"
  },
  {
    "proto": "raw6",
    "recv_q": 0,
    "send_q": 0,
    "local_address": "[::]",
    "foreign_address": "[::]",
    "state": "7",
    "user": "systemd-network",
    "inode": 27001,
    "program_name": "systemd-network",
    "kind": "network",
    "pid": 867,
    "local_port": "ipv6-icmp",
    "foreign_port": "*",
    "transport_protocol": null,
    "network_protocol": "ipv6"
  },
  {
    "proto": "unix",
    "refcnt": 2,
    "flags": null,
    "type": "DGRAM",
    "state": null,
    "inode": 33322,
    "program_name": "systemd",
    "path": "/run/user/1000/systemd/notify",
    "kind": "socket",
    "pid": 1607
  }
]

/etc/passwd file

cat /etc/passwd | jc --passwd -p

[
  {
    "username": "root",
    "password": "*",
    "uid": 0,
    "gid": 0,
    "comment": "System Administrator",
    "home": "/var/root",
    "shell": "/bin/sh"
  },
  {
    "username": "daemon",
    "password": "*",
    "uid": 1,
    "gid": 1,
    "comment": "System Services",
    "home": "/var/root",
    "shell": "/usr/bin/false"
  }
]

ping

ping 8.8.8.8 -c 3 | jc --ping -p          # or:  jc -p ping 8.8.8.8 -c 3

{
  "destination_ip": "8.8.8.8",
  "data_bytes": 56,
  "pattern": null,
  "destination": "8.8.8.8",
  "packets_transmitted": 3,
  "packets_received": 3,
  "packet_loss_percent": 0.0,
  "duplicates": 0,
  "time_ms": 2005.0,
  "round_trip_ms_min": 23.835,
  "round_trip_ms_avg": 30.46,
  "round_trip_ms_max": 34.838,
  "round_trip_ms_stddev": 4.766,
  "responses": [
    {
      "type": "reply",
      "timestamp": null,
      "bytes": 64,
      "response_ip": "8.8.8.8",
      "icmp_seq": 1,
      "ttl": 118,
      "time_ms": 23.8,
      "duplicate": false
    },
    {
      "type": "reply",
      "timestamp": null,
      "bytes": 64,
      "response_ip": "8.8.8.8",
      "icmp_seq": 2,
      "ttl": 118,
      "time_ms": 34.8,
      "duplicate": false
    },
    {
      "type": "reply",
      "timestamp": null,
      "bytes": 64,
      "response_ip": "8.8.8.8",
      "icmp_seq": 3,
      "ttl": 118,
      "time_ms": 32.7,
      "duplicate": false
    }
  ]
}

ps

ps axu | jc --ps -p          # or:  jc -p ps axu

[
  {
    "user": "root",
    "pid": 1,
    "cpu_percent": 0.0,
    "mem_percent": 0.1,
    "vsz": 128072,
    "rss": 6784,
    "tty": null,
    "stat": "Ss",
    "start": "Nov09",
    "time": "0:08",
    "command": "/usr/lib/systemd/systemd --switched-root --system --deseria..."
  },
  {
    "user": "root",
    "pid": 2,
    "cpu_percent": 0.0,
    "mem_percent": 0.0,
    "vsz": 0,
    "rss": 0,
    "tty": null,
    "stat": "S",
    "start": "Nov09",
    "time": "0:00",
    "command": "[kthreadd]"
  },
  {
    "user": "root",
    "pid": 4,
    "cpu_percent": 0.0,
    "mem_percent": 0.0,
    "vsz": 0,
    "rss": 0,
    "tty": null,
    "stat": "S<",
    "start": "Nov09",
    "time": "0:00",
    "command": "[kworker/0:0H]"
  }
]

traceroute

traceroute -m 2 8.8.8.8 | jc --traceroute -p
# or:  jc -p traceroute -m 2 8.8.8.8

{
  "destination_ip": "8.8.8.8",
  "destination_name": "8.8.8.8",
  "hops": [
    {
      "hop": 1,
      "probes": [
        {
          "annotation": null,
          "asn": null,
          "ip": "192.168.1.254",
          "name": "dsldevice.local.net",
          "rtt": 6.616
        },
        {
          "annotation": null,
          "asn": null,
          "ip": "192.168.1.254",
          "name": "dsldevice.local.net",
          "rtt": 6.413
        },
        {
          "annotation": null,
          "asn": null,
          "ip": "192.168.1.254",
          "name": "dsldevice.local.net",
          "rtt": 6.308
        }
      ]
    },
    {
      "hop": 2,
      "probes": [
        {
          "annotation": null,
          "asn": null,
          "ip": "76.220.24.1",
          "name": "76-220-24-1.lightspeed.sntcca.sbcglobal.net",
          "rtt": 29.367
        },
        {
          "annotation": null,
          "asn": null,
          "ip": "76.220.24.1",
          "name": "76-220-24-1.lightspeed.sntcca.sbcglobal.net",
          "rtt": 40.197
        },
        {
          "annotation": null,
          "asn": null,
          "ip": "76.220.24.1",
          "name": "76-220-24-1.lightspeed.sntcca.sbcglobal.net",
          "rtt": 29.162
        }
      ]
    }
  ]
}

uptime

uptime | jc --uptime -p          # or:  jc -p uptime

{
  "time": "11:35",
  "uptime": "3 days, 4:03",
  "users": 5,
  "load_1m": 1.88,
  "load_5m": 2.0,
  "load_15m": 1.94,
  "time_hour": 11,
  "time_minute": 35,
  "time_second": null,
  "uptime_days": 3,
  "uptime_hours": 4,
  "uptime_minutes": 3,
  "uptime_total_seconds": 273780
}

XML files

cat cd_catalog.xml

<?xml version="1.0" encoding="UTF-8"?>
<CATALOG>
  <CD>
    <TITLE>Empire Burlesque</TITLE>
    <ARTIST>Bob Dylan</ARTIST>
    <COUNTRY>USA</COUNTRY>
    <COMPANY>Columbia</COMPANY>
    <PRICE>10.90</PRICE>
    <YEAR>1985</YEAR>
  </CD>
  <CD>
    <TITLE>Hide your heart</TITLE>
    <ARTIST>Bonnie Tyler</ARTIST>
    <COUNTRY>UK</COUNTRY>
    <COMPANY>CBS Records</COMPANY>
    <PRICE>9.90</PRICE>
    <YEAR>1988</YEAR>
  </CD>
  ...

cat cd_catalog.xml | jc --xml -p

{
  "CATALOG": {
    "CD": [
      {
        "TITLE": "Empire Burlesque",
        "ARTIST": "Bob Dylan",
        "COUNTRY": "USA",
        "COMPANY": "Columbia",
        "PRICE": "10.90",
        "YEAR": "1985"
      },
      {
        "TITLE": "Hide your heart",
        "ARTIST": "Bonnie Tyler",
        "COUNTRY": "UK",
        "COMPANY": "CBS Records",
        "PRICE": "9.90",
        "YEAR": "1988"
      }
    ]
  }
}

YAML files

cat istio.yaml 

apiVersion: "authentication.istio.io/v1alpha1"
kind: "Policy"
metadata:
  name: "default"
  namespace: "default"
spec:
  peers:
  - mtls: {}
---
apiVersion: "networking.istio.io/v1alpha3"
kind: "DestinationRule"
metadata:
  name: "default"
  namespace: "default"
spec:
  host: "*.default.svc.cluster.local"
  trafficPolicy:
    tls:
      mode: ISTIO_MUTUAL

cat istio.yaml | jc --yaml -p

[
  {
    "apiVersion": "authentication.istio.io/v1alpha1",
    "kind": "Policy",
    "metadata": {
      "name": "default",
      "namespace": "default"
    },
    "spec": {
      "peers": [
        {
          "mtls": {}
        }
      ]
    }
  },
  {
    "apiVersion": "networking.istio.io/v1alpha3",
    "kind": "DestinationRule",
    "metadata": {
      "name": "default",
      "namespace": "default"
    },
    "spec": {
      "host": "*.default.svc.cluster.local",
      "trafficPolicy": {
        "tls": {
          "mode": "ISTIO_MUTUAL"
        }
      }
    }
  }
]

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