Linux Command - ps

The Linux ps command will show a snapshot of the current running processes on a system.

The ps command has a lot of options. Many of these options are not important and we would be duplicating a lot of obscure documentation if we coverd them here. We are only covering the more useful options here. I am keeping some duplicate options if they are important to know. I’ve excluded some BSD sort keys and some extra format options ( ex: AIX ). If you want a full listing check the man page. This is mostly based off of the ps from the procps-ng package.

• Only keeping the most common and useful options to do most things.

ps       # all procs with same ID and TTYs
ps -ef   # all procs, full listing
ps aux   # similar but BSD options and more useful cols

ps -eo pid,user,args --sort user                   # show all procs, select 3 cols, sort by user
ps -e  -o user:50,pid,command:100,flags            # adjust width of user column to 50, command column to 100

Using -o will override -f and since that is since that was grouped with -e they are both overridden:

ps -ef  -o user:50,pid,command                  #

Lots of info, sorted by cpu and mem:

ps -e -o pid,ppid,euser,pri,ni,stat,wchan,thcount,%mem,vsz,rss,lstart,etime,time,args --sort %cpu
ps -e -o pid,ppid,euser,pri,ni,stat,wchan,thcount,%mem,vsz,rss,lstart,etime,time,args --sort %rss

Option types can be mixed, may have duplicate functionality:

• 1 UNIX options - have a dash, may be grouped
• 2 BSD options - no dash, may be grouped

• 3 GNU long options - two dashes.

• Default: Selects all procs with same effective user ID and same TTY.
• If using BSD options, will also include procs from other TTYs and will display the ‘stat’ field.

SIMPLE PROCESS SELECTION

PROCESS SELECTION BY LIST

   These options accept a single argument in the form of a blank-separated or comma-separated list.  They can be used multiple times.  For example: ps -p "1 2" -p 3,4

OUTPUT FORMAT CONTROL

OUTPUT MODIFIERS

THREAD DISPLAY

Some notes from the man page:

• CPU usage is currently expressed as the percentage of time spent running during the entire lifetime of a process. This is not ideal, and it does not conform to the standards that ps otherwise conforms to. CPU usage is unlikely to add up to exactly 100%.
• The SIZE and RSS fields don’t count some parts of a process including the page tables, kernel stack, struct thread_info, and struct task_struct. This is usually at least 20 KiB of memory that is always resident. SIZE is the virtual size of the process (code+data+stack).
• Processes marked ‘defunct’ are dead processes (so-called “zombies”) that remain because their parent has not destroyed them properly. These processes will be destroyed by init(8) if the parent process exits.

PROCESS FLAGS

The sum of these values is displayed in the “F” column, which is provided by the flags output specifier:

PROCESS STATE CODES

Here are the different values that the s, stat and state output specifiers (header “STAT” or “S”) will display to describe the state of a process:

For BSD formats and when the stat keyword is used, additional characters may be displayed:

STANDARD FORMAT SPECIFIERS

This version of ps includes format specifiers from many other implementations of this tool. There are about 125 of them. See the man page for the full list. I’m just putting what I think is most useful here.

CODE HEADER DESCRIPTION

Process / Thread Info:

Memory Info: