root@app-01:~# true
root@app-01:~# uname -a 2>/dev/null
Linux app-01 6.8.0-51-generic #52-Ubuntu SMP PREEMPT_DYNAMIC Thu Dec 5 13:09:44 UTC 2024 x86_64 GNU/Linux
root@app-01:~# echo P_START; echo P_MID; echo P_END
P_START
P_MID
P_END
root@app-01:~# echo K_START; readlink /proc/$$/exe; head -1 /proc/$$/status; cat /proc/sys/kernel/ostype; cat /proc/sys/kernel/osrelease; cat /proc/uptime; ps -p $$ -o comm= 2>/dev/null; cat /proc/1/comm 2>/dev/null; echo K_END
K_START
cat: /proc/1523/status: No such file or directory
cat: /proc/sys/kernel/ostype: No such file or directory
cat: /proc/sys/kernel/osrelease: No such file or directory
cat: /proc/uptime: No such file or directory
PID TTY TIME CMD
1 ?...... 00:00:02 /sbin/init
445 ?...... 00:00:01 /usr/sbin/sshd -D
534 ?...... 00:00:03 /usr/sbin/nginx: master process
623 ?...... 00:00:00 /usr/sbin/cron -f
712 ?...... 00:00:01 /usr/sbin/mariadbd
845 ?...... 00:00:00 php-fpm: master process
925 ?...... 00:00:00 php-fpm: pool www
926 ?...... 00:00:00 php-fpm: pool www
1523 pts/0.. 00:00:00 -bash
cat: /proc/1/comm: No such file or directory
K_END
-bash: readlink: command not found