Is there a command line tool that will auto pretty-print json? - json

Question

I know that tools like 'jq' can let you add a pipe to the command and format it, but you can't use it for situations like displaying real time json logs from a local server. Is there a tool that can achieve that?

Answer 1

I assume you use a default linux distribution with systemd installed, and all services will communicate with systemd to make protocol entries.
Back in the days linux created log files only, but they got to big. Then they added logrotate to keep it a bit more clean.
A up to date linux distribution uses systemd to store protocol entries, which is much better.
To read a protocol you need to find the service you are looking for first.
To list all services connected with systemd call ...
systemctl list-units | grep service
You could use it without grep if you really cant use pipes.
Anyway, pick the service you like and call its protocol via journalctl. Here are some examples ...
journalctl -u ssh.service -p warning -n 30 # (sudo) last 30 warnings and errors SSH created
journalctl -u apache2.service -p err --no-pager # (sudo) all Apache entries without using the pager (less)
journalctl -k -p err --since today # (sudo) kernel error messages of today
Add the option -o json or -o json-pretty to it and you will have the output you wanted. You can also add option -F or --follow to show most recent journal entries, and continuously print new entries as they are appended to the journal. This way you could make cool backgrounds with conky for example.
You can also get the status of your service via systemctl ...
systemctl status apache2.service # (sudo) status of Apache
This way you can pretty print ...
real time json logs from a local server
like you wanted, and without using jq ...
admin#suse:~$ journalctl -u apache2.service -p warning -n 1 -o json-pretty --no-pager
{
"__CURSOR" : "s=65cbb17b253f44c0b800cee690cfb9ee;i=187fd;b=d3effa777ddf4ba9b4f82f126be4439e;m=51cb2bb2d53;t=54b7c4c9ffbeb;x=9fd3b1bc1e50a798",
"__REALTIME_TIMESTAMP" : "1490372117134315",
"__MONOTONIC_TIMESTAMP" : "5620815834451",
"_BOOT_ID" : "d3effa777ddf4ba9b4f82f126be4439e",
"_TRANSPORT" : "syslog",
"_SYSTEMD_SLICE" : "system.slice",
"_MACHINE_ID" : "dc3b59f36cc34cfa8873c5b530577a2a",
"_HOSTNAME" : "suse",
"SYSLOG_FACILITY" : "1",
"_UID" : "33",
"_GID" : "33",
"PRIORITY" : "4",
"SYSLOG_IDENTIFIER" : "/usr/lib/cgi-bin/captainlog/search.sh",
"MESSAGE" : "Request for the specified frontend is not possible. REMOTE_ADDR: xxxx:xxx:xxxx:xxxx:xxxx:xxxx:xxx:xxxx",
"_COMM" : "logger",
"_CAP_EFFECTIVE" : "0",
"_SYSTEMD_CGROUP" : "/system.slice/apache2.service",
"_SYSTEMD_UNIT" : "apache2.service",
"SYSLOG_PID" : "21314",
"_PID" : "21314",
"_SOURCE_REALTIME_TIMESTAMP" : "1490372117133991"
}
Here is a good guide I found on the internet.