The Linux ps Command: Finding What's Eating Your CPU

The server was sluggish. "Too many processes," they said. But which ones? I typed "ps" and got a screen full of data I couldn't understand.

That day I learned: ps is your window into what's running. Master it.

---

First ps Output

ps

Resulted in:

  PID TTY          TIME CMD
    1 ?        00:00:02 systemd
  412 ?        00:00:01 sshd
  823 pts/0    00:00:00 bash
  824 pts/0    00:00:00 ps

This shows processes for the current terminal only. Not helpful.

BSD style (aux)

ps aux

Shows all processes for all users:

• a = all users
• u = user-oriented format
• x = include processes without terminal

POSIX style (-ef)

ps -ef

Standard format:

• e = every process
• f = full format

---

Understanding ps Columns

USER vs UID

ps -eo user,pid,cmd

User, process ID, command.

CPU and MEM

ps -eo user,pid,pcpu,pmem,cmd

Shows %CPU and %MEM usage.

Sorting by CPU

ps -eo pcpu,pid,user,cmd --sort=-pcpu | head -10

Top CPU consumers.

---

ps Commands That Work

Find a specific process

ps aux | grep nginx

Classic pipeline.

Find by name

ps -C nginx

By command name.

Find by user

ps -U www-data

All processes for user.

Full command with arguments

ps -efww

Wide output for full commands.

Tree view

ps -ejH

Shows parent-child relationships.

Detailed view

ps -Fal

Extra detailed format.

---

The ps Command Builder

Building ps commands with the right fields is easier with the ps Command Builder:

• Select columns from a list
• Choose format easily
• Copy the exact command you need

---

Common ps Patterns

Top 10 by CPU

ps -eo pcpu,pid,user,args --sort=-pcpu | head -n 11

Skip header row (11 = 10 + 1).

Top 10 by memory

ps -eo pmem,pid,user,args --sort=-pmem | head -n 11

All Java processes

ps -C java -o pid=,cmd=

Processes on specific port

lsof -i :8080 | tail -n +2 | awk '{print $2}' | xargs ps -p

Zombie processes

ps aux | grep "defunct"

---

Quick Reference

Command	What It Does
ps	Simple list
ps aux	BSD all users
ps -ef	POSIX full
ps -C name	By command
ps -U user	By user
ps -eo columns	Custom columns
ps --sort=col	Sort output

---

Lessons Learned

1. ps aux is most common — shows everything.

2. Sort by using --sort=-column — minus for descending.

3. Use -eo for custom columns — exactly what you need.

4. Combine with grep — filter specific processes.

5. ps shows current state — for real-time, use top.

---

Conclusion: ps Is Your Process Lens

ps tells you exactly what's running—use it to debug performance issues.

The ps Command Builder makes selecting columns easy.

---

Further Reading

• ps Manual
• ps Command Builder
• Linux Tools Library