The UNIX command for listing processes from the command line is:
ps
“ps” stands for “process status” and by default it will print a list of processes identifiers, controlling terminals, CPU time (user and system), state, and the associated command. Here is the output I see when I type “ps” at the terminal:
$ ps
PID TTY TIME CMD
17559 ttys000 0:00.05 -bash
23627 ttys000 0:00.01 man ps
23630 ttys000 0:00.00 sh -c (cd '/usr/share/man' && /usr/bin/gunzip -c '/usr
23631 ttys000 0:00.00 sh -c (cd '/usr/share/man' && /usr/bin/gunzip -c '/usr
23635 ttys000 0:00.00 sh -c (cd '/usr/share/man' && /usr/bin/gunzip -c '/usr
23638 ttys000 0:00.01 /usr/bin/less -is
18015 ttys001 0:00.14 -bash
23120 ttys001 0:00.09 /Library/Frameworks/Python.framework/Versions/2.6/Reso
23124 ttys001 0:00.01 less
22686 ttys002 0:00.01 -bash
22689 ttys002 0:00.11 /Library/Frameworks/Python.framework/Versions/2.6/Reso
23643 ttys004 0:00.02 -bash
This is neat, and it sort-of tells me what I want to know, but let’s see what else ps can be used for…
Displaying information about a user’s processes
Perhaps the most useful argument for ps is -U. This will list the User ID, Process ID, Terminal, System TIme, and Command associated with each ’s processes:
$ ps -U root
UID PID TTY TIME CMD
0 1 ?? 8:27.52 /sbin/launchd
0 10 ?? 0:12.99 /usr/libexec/kextd
0 11 ?? 0:27.03 /usr/sbin/DirectoryService
0 12 ?? 0:05.74 /usr/sbin/notifyd
0 13 ?? 0:02.45 /usr/sbin/diskarbitrationd
0 14 ?? 0:34.34 /usr/libexec/configd
0 15 ?? 0:23.02 /usr/sbin/syslogd
0 21 ?? 0:02.53 /usr/sbin/securityd -i
0 23 ?? 0:01.38 /usr/sbin/blued
0 27 ?? 0:01.29 /usr/sbin/krb5kdc -n
...
If working with User IDs is more convenient, I can use “ps -u " to list the same information by user ID instead of user name.
Displaying detailed information about processes
To obtain detailed information about processes, supply the “-v” argument. Note: this argument prints more columns of information than the terminal is capable of displaying if left at the typical 80x24 (80 columns, 24 rows) configuration. This argument can be supplied with other arguments, such as “-u.” The following will output detailed information about all of root’s processes:
$ ps -vU root
PID STAT TIME SL RE PAGEIN VSZ RSS LIM TSIZ %CPU %MEM COMMAND
17433 Ss 39:13.05 0 0 0 3226576 148012 - 0 0.6 1.8 /
35 Ss 2:20.87 0 0 0 2649356 74160 - 0 0.0 0.9 /
69 Ss 0:32.61 0 0 0 2507432 42324 - 0 0.0 0.5 /
10 Ss 0:12.99 0 0 0 2458608 13352 - 0 0.0 0.2 /
17432 Ss 0:15.13 0 0 0 2798580 10820 - 0 0.0 0.1 /
11 Ss 0:27.07 0 0 0 2452852 6076 - 0 0.0 0.1 /
23 Ss 0:01.38 0 0 0 2461316 4348 - 0 0.0 0.1 /
21 Ss 0:02.53 0 0 0 2459436 4116 - 0 0.0 0.0 /
68 Ss 1:08.24 0 0 0 2461216 3596 - 0 0.0 0.0 /
40 Ss 0:20.31 0 0 0 2453200 3440 - 0 0.0 0.0 /
14 Ss 0:34.36 0 0 0 2474800 3436 - 0 0.0 0.0 /
364 Ss 0:04.07 0 0 0 2450680 2468 - 0 0.0 0.0 /
51 Ss 37:06.24 0 0 0 101452 2228 - 0 0.2 0.0 /
27 Ss 0:01.30 0 0 0 2448456 1992 - 0 0.0 0.0 /
39 Ss 12:27.64 0 0 0 2447776 1592 - 0 0.0 0.0 /
13 Ss 0:02.45 0 0 0 2446968 1540 - 0 0.0 0.0 /
1 Ss 8:29.82 0 0 0 2456848 1528 - 0 0.0 0.0 /
93 Ss 0:04.38 0 0 0 2436424 1440 - 0 0.0 0.0 /
20523 Ss 0:05.39 0 0 0 2435292 1148 - 0 0.0 0.0 /
37 Ss 0:02.34 0 0 0 2445904 1076 - 0 0.0 0.0 /
48 Ss 0:00.98 0 0 0 2446832 988 - 0 0.0 0.0 a
77 Ss 0:00.04 0 0 0 2438260 924 - 0 0.0 0.0 /
11253 Ss 0:00.38 0 0 0 2436128 900 - 0 0.0 0.0 /
15 Ss 0:23.03 0 0 0 2457256 868 - 0 0.0 0.0 /
42 Ss 0:00.04 0 0 0 2434864 788 - 0 0.0 0.0 /
12 Ss 0:05.75 0 0 0 2444624 640 - 0 0.0 0.0 /
366 S 0:00.00 0 0 0 2439212 336 - 0 0.0 0.0 /
It can be easier to deal with this much information by outputting it to a file and opening it with a text editor:
$ ps -vU root > rootprocs.txt
$ open rootprocs.txt
The detailed information provided includes:
- Process ID - The identifier assigned to this process
- State - Indicated by a sequence of characters, the first character indicates the run state of the process:
I - Idle process (sleeping > 20 seconds)
R - Runnable process
S - Sleeping process ( < 20 seconds )
T - Stopped process
U - Process in uninterruptible wait
Z - Dead (or "Zombie") process
Any characters following these indicate additional state information:
+ - Process is in foreground process group of its control terminal
< - Process has raised CPU scheduling priority
> - Process has a specified soft limit on memory
A - Process has asked for random page replacement
E - Process is trying to exit
L - Process has pages locked in core (raw Input/Output)
N - Process has reduced CPU scheduling priority
S - Process has asked for First In, First Out page replacements - Process is a session leader
V - Process is suspended during a vfork(2)
W - Process is swapped out
X - Process is being traced or debugged
- Time - Real time during which the process has been running
- VSZ - Virtual memory usage of of the process.
- RSS - The real memory (resident set) size of the process in 1024-byte units.
- LIM - The soft limit on memory used specified by the “setrlimit()” system call. The soft limit is the value enforced by the kernel for memory allocated to this process.
- %CPU - The CPU utilization of the process; this is a decaying average over up to a minute of previous (real) time. It is possible for the sum of all processes to exceed 100%.
- %MEM - The percentage of physical memory used by this process.
- COMMAND - The command that originated the process.
I am not sure what the SL, RE, PageIn, and TSIZ categories stand for. Any ideas?
Usefulness
After the research that went into writing this, I’ve determined that the most useful usage of ps for me is going to be to supply the “aux” arguments. These will display all processes belonging to all users including processes which do not have a controlling terminal. This means that typing
$ ps -aux
will display all processes running on the system including information about:
USER - The user account that originated the process PID - Process Identifier %CPU - See above - CPU utilization of the process %MEM - See above - Percentage of real memory used by the process VSZ - See above - Virtual memory usage by the process RSS - See above - Real memory usage of the process TT - Abbreviation for the pathname of the controlling terminal, if any. This consists of the three letters following /dev/tty. STAT - See above - the current state of the process STARTED - When the process was started, parsed for humans TIME - See above - how long the process has been running COMMAND - See above - the command that spawned the process
Again, it might be useful to output the results of ps -aux to a file for
easier viewing than in the terminal window, or for reporting purposes.
I can supply parameters to ps -aux to narrow my search, for instance, to
retrieve information about the process with ID 1, I would type
$ ps aux 1
USER PID %CPU %MEM VSZ RSS TT STAT STARTED TIME COMMAND
root 1 0.4 0.0 2456852 1532 ?? Ss 9Jun12 8:38.87 /sbin/launch
Since I cannot supply a username to ps -aux I’ve found the easiest way to find
information relevant to a particular username would be to pipe the results to
grep and then output the results to a file for reviewing.
$ ps aux | grep root > rootprocs.txt
To wrap this up, ps is a very flexible and powerful command.