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jq hack #1: colored less

September 28, 2020

Sometimes you want to look at a lot of JSON output in the terminal. Sometimes this JSON output is nicely formatted, and often it is compacted by a REST endpoint. Examples of verbose output:

$ kubectl get nodes -o json
$ curl 'https://hacker-news.firebaseio.com/v0/topstories.json'

In both cases you can pipe the output through:

$ ... | jq -C . | less -R

The -C parameter to jq forces colors. When omitted, jq will only print colors when an interactive terminal is detected. Piping further into less removes the colors. Additionally, we have to tell less to interpolate those ANSI colors so that we don't see a bunch of ESC[1;39m codes.

$ kubectl get nodes -o json | jq -C . | less -R
{
  "apiVersion": "v1",
  "items": [
    {
      "apiVersion": "v1",
      "kind": "Node",
      "metadata": {
        "annotations": {
...
:

Here,

  • jq -C:
    --color-output / -C and --monochrome-output / -M:
    
    By default, jq outputs colored JSON if writing to a terminal.
    You can force it to produce color even if writing to a pipe
    or a file using -C, and disable color with -M.
    
  • less -R:
    -R or --RAW-CONTROL-CHARS
    
    Like -r, but only ANSI "color" escape sequences are output in
    "raw" form. Unlike -r, the screen appearance is maintained
    correctly in most cases. ANSI "color" escape sequences are
    sequences of the form:
    
        ESC [ ... m
    
    where the "..." is zero or more color specification characters.
    For the purpose of keeping track of screen appearance, ANSI color
    escape sequences are assumed to not move the cursor. [...]