singularity

用户问题

using kubectl how can i see the logs for a pod

ChatGPT

Use:

kubectl logs

If the pod has multiple containers:

kubectl logs  -c

For live streaming logs:

kubectl logs -f

For previous instance (e.g. after crash):

kubectl logs --previous

You can combine flags too:

kubectl logs -f --previous  -c

用户问题

can i prettify this json output with grep or something?

ChatGPT

grep won’t prettify JSON—it just filters lines. Use jq instead. Pipe the output:

kubectl logs  | jq

For container logs:

kubectl logs  -c  | jq

If the logs aren’t valid JSON per line, you can try:

kubectl logs  | jq -R 'fromjson?'

That tries to parse each line as JSON, skipping invalid ones.

用户问题

jq after few entries “parse error: Invalid numeric literal at line 6, column 11”

ChatGPT

That error usually means your logs include lines that aren’t valid JSON—possibly malformed entries, plain text, or partial lines.

Here’s how to handle that robustly:

Option 1: Best-effort line-by-line JSON parsing

kubectl logs  | jq -R 'fromjson?'

This treats each line as a raw string (-R), attempts to parse as JSON (fromjson?), and skips lines that fail.

Option 2: Filter only valid JSON lines first (if they’re easily greppable)

If you know valid entries start with {, for example:

kubectl logs  | grep '^{.*}' | jq -R 'fromjson?'

Option 3: Debug problematic lines

To find and inspect the bad entries:

kubectl logs  | jq -R 'try fromjson catch .'

This shows raw lines on failure instead of skipping them—useful for debugging.

Want to isolate only the malformed lines?:

kubectl logs  | jq -R 'select(try fromjson | not)'

Let me know if you’re working with multi-line JSON or structured log formats (e.g., GCP-style).

用户问题

i am getting a bunch of json formatted logs with the following command kubectl logs -f deployment-backend-847d585f47-sc55p | jq -R ‘fromjson? | select(.user_agent | test(“SURAJ”))’

each incoming json object has a “time” key with the value being formatted thusly “2025-04-14T19:28:06.643848075Z”

using my jq command, is it possible to humanize this time field and change it to a more readable format?

ChatGPT

Yes. jq doesn’t natively parse RFC3339 nanosecond timestamps, but you can trim and parse it to a readable format with a little string work.

Example:

kubectl logs -f deployment-backend-847d585f47-sc55p \
  | jq -R 'fromjson? 
    | select(.user_agent | test("SURAJ")) 
    | .time = (.time | sub("\\..*"; "") | fromdateiso8601 | strftime("%Y-%m-%d %H:%M:%S"))'

What this does:

You can of course change the format string to anything you prefer, e.g.:

"%Y-%m-%d %H:%M:%S"
"%b %d %H:%M"
"%I:%M:%S %p"

Let me know if you want to append the human-readable time instead of replacing the original.

用户问题

this command does not work, i can see it running but i see no logs no output

ChatGPT

Thanks—likely cause: fromjson? fails silently when .time isn’t present or the timestamp can’t be parsed (due to the nanoseconds). Let’s isolate and validate step by step.

✅ Step-by-step fix:

  1. Inspect raw lines first:
kubectl logs -f deployment-backend-847d585f47-sc55p | head -n 5

Ensure each line is valid JSON with a .time field.

  1. Test just parsing and displaying .time:
kubectl logs -f deployment-backend-847d585f47-sc55p \
  | jq -R 'fromjson? | select(.time) | {time: .time}'
  1. Now trim nanoseconds, parse, and format:
kubectl logs -f deployment-backend-847d585f47-sc55p \
  | jq -R '
      fromjson? 
      | select(.user_agent | test("SURAJ")) 
      | select(.time)
      | .human_time = (.time | sub("\\..*"; "") | fromdateiso8601 | strftime("%Y-%m-%d %H:%M:%S"))
    '

🛠️ Why this version works:

Let me know if you want to filter time range or change the output structure.

用户问题

the first two work fine, i can see each log has time but the third one gives no output

ChatGPT

Got it. That points to the issue being in this part:

sub("\\..*"; "")

This regex removes everything from the dot onward—including the trailing Z, which fromdateiso8601 requires.

✅ Fix: keep the trailing Z

Use this instead:

sub("\\.[0-9]+Z$"; "Z")

Full working command:

kubectl logs -f deployment-backend-847d585f47-sc55p \
  | jq -R '
      fromjson? 
      | select(.user_agent | test("SURAJ")) 
      | select(.time)
      | .human_time = (
          .time 
          | sub("\\.[0-9]+Z$"; "Z") 
          | fromdateiso8601 
          | strftime("%Y-%m-%d %H:%M:%S")
        )
    '

This trims only the nanoseconds, preserves the Z, and parses correctly.

Let me know if you want time replaced instead of duplicated as human_time.

用户问题

make this last command an alias, add it to my zshrc call it klog-cua

ChatGPT

Add this to your ~/.zshrc:

alias klog-cua='kubectl logs -f deployment-backend-847d585f47-sc55p | jq -R '\''fromjson? | select(.user_agent | test("SURAJ")) | select(.time) | .human_time = (.time | sub("\\.[0-9]+Z$"; "Z") | fromdateiso8601 | strftime("%Y-%m-%d %H:%M:%S"))'\'''

Then run:

source ~/.zshrc

Now you can just run:

klog-cua

Let me know if you want to parameterize the pod name or the user-agent match string.

用户问题

any way to list all available aliases in zsh?

ChatGPT

Yes—just run:

alias

That lists all currently defined aliases in your Zsh session.

To find a specific one (e.g., klog-cua):

alias | grep klog-cua

To list aliases defined in your zshrc (not inherited), you can also grep your config:

grep '^alias' ~/.zshrc

Let me know if you want a function instead—more flexible than an alias if you’re planning to pass args.