$ pidof apache2
31751 31750 31749 31748 31747 31489 31488 31487 31486 31485 1500

$ ps aux | grep apache2 | grep -v grep | awk -n '{print $2}'
1500
31485
31486
31487
31488
31489
31747
31748
31749
31750
31751

$ ps aux | grep apache2 | grep -v grep | awk -n '{printf $2" "}'
1500 31485 31486 31487 31488 31489 31747 31748 31749 31750 31751

$ date +%T:%N; pidof apache2 ;  date +%T:%N
17:06:05:627088798
31751 31750 31749 31748 31747 31489 31488 31487 31486 31485 1500
17:06:05:634500908

$ date +%T:%N; ps aux | grep apache2 | grep -v grep | awk -n '{printf $2" "}' ;  date +%T:%N
17:06:29:887314682
1500 31485 31486 31487 31488 31489 31747 31748 31749 31750 31751
17:06:29:903997288

$ ps aux | grep apache2 | grep -v grep | awk -n '{print $2}' | sort -rn
31751
31750
31749
31748
31747
31489
31488
31487
31486
31485
1500

$ ps ax | grep firefox
8621 ??  S       5:20.24 firefox
10409 p3  R+      0:00.00 grep firefox

$ ps -ef | pgrep login
102
103
6245
6361

$ ps -ef | pgrep login | sort -rn
6361
6245
103
102

$ ps -ef | pgrep login | sort -rn | head -n 1
6361