How to get all process ids without ps command on Linux？

On Linux, all running process have "metadata" stored in the /proc filesystem.

#  for exe in /proc/*/exe; do ls -l $exe; done

# man  ps  

# ps -C sshd --no-header

# ps -C dockerd --no-header

-C cmdlist

Select by command name.  This selects the processes whose executable name is given in cmdlist.

you can use the long options --headers and --no-headers to enable printing headers each page or disable headers entirely, respectively.

#  ps -eo nlwp,pcpu,user,pid,ppid,args  --sort nlwp  

注：以 nlwp排序，默认正序

LWP -- 轻量级进程，即线程

NLWP --线程数，即 number of threads in process

#  ps -eo pid,cmd,%mem,%cpu --sort=-%mem

Thecommand is highly valuable for system admins during troubleshooting the system. 

You can display the processes list in a sorted manner to find out the highest memory usage processes.

#  ps -mp   ${pid}    -o   THREAD,tid,time

参数解释：

   -m:显示所有的线程

   -p:pid进程使用CPU的时间

   -o:该参数后是用户自定义格式。

  如：THREAD,tid,time表示线程、线程ID号、线程占用的时间。

$ ps -Hp   ${pid}  

参考

ps(1) — Linux manual page

https://man7.org/linux/man-pages/man1/ps.1.html

Linux PS command with examples

https://www.fosslinux.com/43296/linux-ps-command-with-examples.htm

How to get all process ids without ps command on Linux？

https://stackoverflow.com/questions/32913424/how-to-get-all-process-ids-without-ps-command-on-linux

What is the difference between ps and top command?

https://unix.stackexchange.com/questions/62176/what-is-the-difference-between-ps-and-top-command