jq – commandline JSON processor

What are JSON and CSV formats?

JSON is an acronym for JavaScript Object Notation. Often used in web apps, but it is not limited to JavaScript. One can use any programming language such as Perl, Python or CLI tools such as jq.

CSV is an acronym for Comma-separated values. It is a text file you can use in spreadsheet apps, programming languages and many other apps.

Installing jq

Since jq is available in most common repos, I will use that one for my needs. Here is how to install jq on a Debian or Ubuntu Linux using the apt command/apt-get command:

$ sudo apt install jq

RHEL/Fedora/CentOS/Alma/Rocky Linux user try the dnf command:

$ sudo dnf install jq

Alpine Linux user try the apk command:

$ sudo apk add jq

SUSE or OpenSUSE Linux user try the zypper command:

$ sudo zypper in jq

macOS / OS X user install homebrew and then use the brew command:

$ brew install jq


$ jq -h
jq - commandline JSON processor [version 1.6]

Usage:  jq [options] <jq filter> [file...]
        jq [options] --args <jq filter> [strings...]
        jq [options] --jsonargs <jq filter> [JSON_TEXTS...]

jq is a tool for processing JSON inputs, applying the given filter to
its JSON text inputs and producing the filter's results as JSON on
standard output.

The simplest filter is ., which copies jq's input to its output
unmodified (except for formatting, but note that IEEE754 is used
for number representation internally, with all that that implies).

For more advanced filters see the jq(1) manpage ("man jq")
and/or https://stedolan.github.io/jq


        $ echo '{"foo": 0}' | jq .
                "foo": 0

Some of the options include:
  -c               compact instead of pretty-printed output;
  -n               use `null` as the single input value;
  -e               set the exit status code based on the output;
  -s               read (slurp) all inputs into an array; apply filter to it;
  -r               output raw strings, not JSON texts;
  -R               read raw strings, not JSON texts;
  -C               colorize JSON;
  -M               monochrome (don't colorize JSON);
  -S               sort keys of objects on output;
  --tab            use tabs for indentation;
  --arg a v        set variable $a to value <v>;
  --argjson a v    set variable $a to JSON value <v>;
  --slurpfile a f  set variable $a to an array of JSON texts read from <f>;
  --rawfile a f    set variable $a to a string consisting of the contents of <f>;
  --args           remaining arguments are string arguments, not files;
  --jsonargs       remaining arguments are JSON arguments, not files;
  --               terminates argument processing;

Named arguments are also available as $ARGS.named[], while
positional arguments are available as $ARGS.positional[].

See the manpage for more options.

ตัวอย่างไฟล์ df.json

    "fs": "/dev/mapper/vgubuntu-root",
    "type": "ext4",
    "size": "915G",
    "used": "135G",
    "avail": "734G",
    "usedpercentage": "16%",
    "mounted": "/"
    "fs": "/dev/nvme0n1p2",
    "type": "ext4",
    "size": "1.4G",
    "used": "378M",
    "avail": "939M",
    "usedpercentage": "29%",
    "mounted": "/boot"
    "fs": "/dev/nvme0n1p1",
    "type": "vfat",
    "size": "511M",
    "used": "30M",
    "avail": "482M",
    "usedpercentage": "6%",
    "mounted": "/boot/efi"

convert JSON to CSV

$ cat df.json | jq -r '.[]| join(",")'
$ cat df.json | jq -r '.[]| join(",")' > df.csv
$ cat df.csv