How can I view information about running processes on Ubuntu, without using ps, through the proc directory?

How to view information about running processes on Ubuntu without using ps, via the directory proc through the terminal? I don't quite understand

 1
linux
Author: tsukirin, 2020-12-01
Source

1 answers

pushd /proc/

for pid in [0-9]*
do
  printf "\n${pid}\t"
  cat $pid/cmdline
done

popd
 0
Author: eri, 2020-12-01 14:45:10