TweetFollow Us on Twitter

Process Control

Volume Number: 18 (2002)
Issue Number: 10
Column Tag: Section 7

Process Control

ps, top, kill, ...

by Rich Morin

A recent foray into Internet Radio conflicted in some manner with the OSX screen saver on my desktop machine. As a result, I was unable to get the screen saver to go away. I tried all of the usual tricks: hitting mouse buttons, moving the mouse, advancing to keyboard keys (e.g., shift, return) and finally "magic key combinations" (e.g., command-option-escape). No luck.

On Mac OS 9, my next steps would have been to try a "three-finger salute" (i.e., command-control-power), followed by pushing the reset button and if need be, pulling the plug. This being a BSD-based machine, however, I had a better solution at hand.

I went to another machine on the local net, logged into my desktop machine, and killed a couple of sorely-confused processes. I then logged out and returned to my desk, flushed with victory and the knowledge that I had a useful Section 7 topic in hand.

Advance Preparation

My "remote login" trick wouldn't have worked without a bit of advance preparation. OSX, for very good reasons, turns off most "remote services", by default. I don't recommend turning services on, willy-nilly, but ftp and ssh are so handy that I wouldn't want to live without them. And, because my desktop machine is hidden behind a firewall, I consider the risk to be pretty minimal (your mileage may vary).

In any case, here's how to allow remote ftp and ssh on an OSX 10.2 machine: In the System Preferences application, select the Sharing dialog. Under the "Services" tab, turn on the checkboxes labelled "FTP Access" and "Rmote Login".

You will also need a way to "find" your machine from the other one. This can be achieved in any number of ways, including DNS (Domain Name System), /etc/hosts files, etc. Your network administrator will (or should :-) know how to make this happen on your local network. As a last resort, you can use your machine's IP (Internet Protocol) address as a name.

Logging In

Because ftp and ssh aren't OSX-specific tools, you can log in remotely from almost any operating system. This being an OSX-related column, however, I'll assume that you're running OSX. If you're not, you'll have to deal with the vagaries of installing and starting up the needed clients on the machine you're on. On OSX, just start up a Terminal window and type:

% ssh <me>@<mydesk>
<me>@<mydesk>s password:

The first time you do this from a given machine, you'll be asked whether you trust the SSH keys on your desktop machine. Say yes (:-). After entering your password, you'll get a prompt from your desktop machine:

<me>@<mydesk> [~] 1: 

There are all sorts of things you can do at this point, but try not to get too excited and do something you'll regret. Think "delicate surgery", rather than "hack and slash". Thus, the first thing we want to do is find out a bit about the programs that are running over on the desktop machine. To do this, we'll use the top command, which displays system usage statistics and then lists the top processes, in terms of CPU utilization:

<me>@<mydesk> [~] 2: top
Processes:  65 total, 3 running, 62 sleeping... 190 threads   17:39:16
Load Avg:   2.15, 1.46, 1.35
CPU usage:  62.3% user, 37.7% sys, 0.0% idle
SharedLibs: num =  116, resident = 23.2M code, ...
MemRegions: num = 4936, resident =  159M + 13.0M private, ...
VM:         4.22G + 45.8M  5363(0) pageins, 0(0) pageouts   
   PID COMMAND            %CPU      TIME         ...
   758 top                7.9%      0:38.79   ...
   703 tcsh               0.0%      0:00.34   ...
   702 sshd               0.0%      0:00.78   ...
   701 ssh                0.0%      0:00.86   ...
   692 CCacheServ         0.0%      0:06.09   ...
   610 Finder             0.0%      0:18.75   ... 
   ...

Unlike most BSD commands, top doesn't just run and go away. Instead, it refreshes its display about once a second, letting you see if things are changing. When you're done viewing the display, type "q" (or Conrtol-C) and the program will terminate. Alternatively, just start up another Terminal window, leaving top running in the first one...

The system usage statistics are a bit arcane; look at top's man page if you want the details. For now, just note that the number of processes should normally be under 100 and that the load average (time-averaged system load) should be under five. If you see higher values on your machine, you may have a runaway application.

Because top's process list is sorted by CPU utilization, active programs tend to "bubble up". So, look near the top of the list for suspects. In some cases, killing off a sijngle process won't be enough; to restore my desktop to proper functionality, I had to kill the screen saver, the Internet Radio application, and the Finder!

I issued a separate kill com mand for each process I wanted to terminate, specifying the PID (process ID). This let me see and evaluate the effect of each action:

^C<me>@<mydesk> [~] 3: kill -9 610

Be sure to get the PID right; you don't want to kill off an innocent application, by mistake! By the way, kill can do more than just terminate processes. It can send any desired "signal" to one or more specified processes. So, for example, it can be used to tell processes to check their configuration files, etc.

If you can't figure out which command you need to kill, you may need to get a different view of the information. The ps command lists "process status" information, in a variety of formats. For our present purposes, "ps awx" is a reasonable idiom:

<me>@<mydesk> [~] 4: ps awx
  PID  TT  STAT      TIME COMMAND
    1  ??  SLs    0:00.03 /sbin/init     
    2  ??  SL     0:02.35 /sbin/mach_init        
   41  ??  Ss     0:02.24 kextd
  ...

To list the commands in a different order, just pipe together some commands:

<me>@<mydesk> [~] 5: ps awx | sort +3 -rn | more
   62  ??  Ss    56:09.79 .../WindowServer
  ...
  PID  TT  STAT      TIME COMMAND
  994 std  R+     0:00.00 more
  993 std  R+     0:00.01 sort +3 -rn
  ...
  610  ??  S      0:18.80 .../MacOS/Finder -psn_0_3538945
  ...

Transliterated, the pipeline above says to run the output of ps through a line-oriented sort (sorting by the fourth column, in reverse numeric order), then pipe the result through more (a text viewing command). If you know what command you're looking for, of course, you can use grep:

<me>@<mydesk> [~] 6: ps awx | grep Finder
 1006 std  R+     0:00.00 grep Finder
  610  ??  S      0:18.80 .../Finder -psn_0_3538945

With the advent of OSX 10.2, I feel more comfortable in recommending FreeBSD-related books to OSX users and programmers. There are still some differences, to be sure, but any book that covers FreeBSD 4.X commands will be a good match for the OSX 10.2 command set.

Although processes are the workhorses of any BSD system, there are few books that spend much time on them. Quite a few man pages relate to processes, however, and the DOSSIER (www.ptf.com/dossier) volume "Processes: FreeBSD" brings them together in a single volume.


Rich Morin has been using computers since 1970, Unix since 1983, and Mac-based Unix since 1986 (when he helped Apple create A/UX 1.0). When he isn't writing this column, Rich runs Prime Time Freeware (www.ptf.com), a publisher of books and CD-ROMs for the Free and Open Source software community. Feel free to write to Rich at rdm@ptf.com.

 
AAPL
$102.50
Apple Inc.
+0.25
MSFT
$45.43
Microsoft Corpora
+0.55
GOOG
$571.60
Google Inc.
+2.40

MacTech Search:
Community Search:

Software Updates via MacUpdate

Path Finder 6.5.5 - Powerful, award-winn...
Path Finder is a file browser that combines the familiar Finder interface with the powerful utilities and innovative features. Just a small selection of the Path Finder 6 feature set: Dual pane... Read more
QuarkXPress 10.2.1 - Desktop publishing...
With QuarkXPress, you can communicate in all the ways you need to -- and always look professional -- in print and digital media, all in a single tool. Features include: Easy to Use -- QuarkXPress is... Read more
Skype 6.19.0.450 - Voice-over-internet p...
Skype allows you to talk to friends, family and co-workers across the Internet without the inconvenience of long distance telephone charges. Using peer-to-peer data transmission technology, Skype... Read more
VueScan 9.4.41 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Cloud 3.0.0 - File sharing from your men...
Cloud is simple file sharing for the Mac. Drag a file from your Mac to the CloudApp icon in the menubar and we take care of the rest. A link to the file will automatically be copied to your clipboard... Read more
LibreOffice 4.3.1.2 - Free Open Source o...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
SlingPlayer Plugin 3.3.20.505 - Browser...
SlingPlayer is the screen interface software that works hand-in-hand with the hardware inside the Slingbox to make your TV viewing experience just like that at home. It features an array of... Read more
Get Lyrical 3.8 - Auto-magically adds ly...
Get Lyrical auto-magically add lyrics to songs in iTunes. You can choose either a selection of tracks, or the current track. Or turn on "Active Tagging" to get lyrics for songs as you play them.... Read more
Viber 4.2.2 - Send messages and make cal...
Viber lets you send free messages and make free calls to other Viber users, on any device and network, in any country! Viber syncs your contacts, messages and call history with your mobile device,... Read more
Cocktail 7.6 - General maintenance and o...
Cocktail is a general purpose utility for OS X that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more

Latest Forum Discussions

See All

Rhonna Designs Magic (Photography)
Rhonna Designs Magic 1.0 Device: iOS Universal Category: Photography Price: $1.99, Version: 1.0 (iTunes) Description: Want to sprinkle *magic* on your photos? With RD Magic, you can add colors, filters, light leaks, bokeh, edges,... | Read more »
This Week at 148Apps: August 25-29, 2014
Shiny Happy App Reviews   | Read more »
Qube Kingdom – Tips, Tricks, Strategies,...
Qube Kingdom is a tower defense game from DeNA. You rally your troops – magicians, archers, knights, barbarians, and others – and fight against an evil menace looking to dominate your kingdom of tiny squares. Planning a war isn’t easy, so here are a... | Read more »
Qube Kingdom Review
Qube Kingdom Review By Nadia Oxford on August 29th, 2014 Our Rating: :: KIND OF A SQUARE KINGDOMUniversal App - Designed for iPhone and iPad Qube Kingdom has cute visuals, but it’s a pretty basic tower defense game at heart.   | Read more »
Fire in the Hole Review
Fire in the Hole Review By Rob Thomas on August 29th, 2014 Our Rating: :: WALK THE PLANKUniversal App - Designed for iPhone and iPad Seafoam’s Fire in the Hole looks like a bright, 8-bit throwback, but there’s not enough booty to... | Read more »
Alien Creeps TD is Now Available Worldwi...
Alien Creeps TD is Now Available Worldwide Posted by Ellis Spice on August 29th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Dodo Master Review
Dodo Master Review By Jordan Minor on August 29th, 2014 Our Rating: :: NEST EGGiPad Only App - Designed for the iPad Dodo Master is tough but fair, and that’s what makes it a joy to play.   | Read more »
Motorsport Manager Review
Motorsport Manager Review By Lee Hamlet on August 29th, 2014 Our Rating: :: MARVELOUS MANAGEMENTUniversal App - Designed for iPhone and iPad Despite its depth and sense of tactical freedom, Motorsport Manager is one of the most... | Read more »
Motorsport Manager – Beginner Tips, Tric...
The world of Motorsport management can be an unforgiving and merciless one, so to help with some of the stress that comes with running a successful race team, here are a few hints and tips to leave your opponents in the dust. | Read more »
CalPal Update Brings the App to 2.0, Add...
CalPal Update Brings the App to 2.0, Adds Lots of New Stuff Posted by Ellis Spice on August 29th, 2014 [ permalink ] | Read more »

Price Scanner via MacPrices.net

Are We Now In The Post-Post-PC Era?
A longtime and thoroughgoing laptop aficionado, I was more than a little dismayed by Steve Jobs’s declaration back in 2010 when he sprang the iPad on an unsuspecting world. that we’d entered a “post-... Read more
Apple now offering refurbished 21-inch 1.4GHz...
The Apple Store is now offering Apple Certified Refurbished 21″ 1.4GHz iMacs for $929 including free shipping plus Apple’s standard one-year warranty. Their price is $170 off the cost of new models,... Read more
Save $50 on the 2.5GHz Mac mini, on sale for...
B&H Photo has the 2.5GHz Mac mini on sale for $549.99 including free shipping. That’s $50 off MSRP, and B&H will also include a free copy of Parallels Desktop software. NY sales tax only. Read more
Save up to $300 on an iMac with Apple refurbi...
The Apple Store has Apple Certified Refurbished iMacs available for up to $300 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free. These are the best prices on... Read more
The Rise of Phablets
Carlisle & Gallagher Consulting Group, a businesses and technology consulting firm focused solely on the financial services industry, has released an infographic depicting the convergence of... Read more
Bad Driver Database App Allows Good Drivers t...
Bad Driver Database 1.4 by Facile Group is a new iOS and Android app that lets users instantly input and see how many times a careless, reckless or just plain stupid driver has been added to the... Read more
Eddy – Cloud Music Player for iPhone/iPad Fre...
Ukraine based CapableBits announces the release of Eddy, its tiny, but smart and powerful cloud music player for iPhone and iPad that allows users to stream or download music directly from cloud... Read more
A&D Medical Launches Its WellnessConnecte...
For consumers and the healthcare providers and loved ones who care for them, A&D Medical, a leader in connected health and biometric measurement devices and services, has launched its... Read more
Anand Lal Shimpi Retires From AnandTech
Anand Lal Shimpi, whose AnandTech Website is famous for its meticulously detailed and thoroughgoing reviews and analysis, is packing it in. Lal Shimpi, who founded the tech site at age 14 in 1997,... Read more
2.5GHz Mac mini, Apple refurbished, in stock...
The Apple Store has Apple Certified Refurbished 2.5GHz Mac minis available for $509, $90 off MSRP. Apple’s one-year warranty is included, and shipping is free. Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.