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
$567.77
Apple Inc.
+43.02
MSFT
$39.86
Microsoft Corpora
+0.17
GOOG
$525.16
Google Inc.
-1.78

MacTech Search:
Community Search:

Software Updates via MacUpdate

Ember 1.5.1 - Versatile digital scrapboo...
Ember (formerly LittleSnapper) is your digital scrapbook of things that inspire you: websites, photos, apps or other things. Just drag in images that you want to keep, organize them into relevant... Read more
Cyberduck 4.4.4 - FTP and SFTP browser....
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more
TechTool Pro 7.0.3 - Hard drive and syst...
TechTool Pro is now 7, and this is the most advanced version of the acclaimed Macintosh troubleshooting utility created in its 20-year history. Micromat has redeveloped TechTool Pro 7 to be fully 64... Read more
MacFamilyTree 7.1.6 - Create and explore...
MacFamilyTree gives genealogy a facelift: it's modern, interactive, incredibly fast, and easy to use. We're convinced that generations of chroniclers would have loved to trade in their genealogy... Read more
EtreCheck 1.9.9 - For troubleshooting yo...
EtreCheck is a simple little app to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support... Read more
TeamViewer 9.0.28116 - Establish remote...
TeamViewer gives you remote control of any computer or Mac over the Internet within seconds, or can be used for online meetings. Find out why more than 200 million users trust TeamViewer! Free for... Read more
DiskAid 6.6.3 - Use your iOS device as a...
DiskAid is the ultimate transfer tool for accessing the iPod, iPhone or iPad directly from the desktop. Access data such as: music, video, photos, contacts, notes, call history, text messages (SMS),... Read more
Viber 4.1.0 - 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
Apple iOS 7.1.1 - The latest version of...
The latest version of iOS can be downloaded through iTunes. Apple iOS 7 brings an all-new design and all-new features. Simplicity Simplicity is often equated with minimalism. Yet true simplicity is... Read more
1Password 4.3 - Powerful password manage...
1Password is a password manager that uniquely brings you both security and convenience. It is the only program that provides anti-phishing protection and goes beyond password management by adding Web... Read more

Latest Forum Discussions

See All

Pen & Ink Review
Pen & Ink Review By Jennifer Allen on April 24th, 2014 Our Rating: :: CONVENIENT ARTISTRYiPad Only App - Designed for the iPad Pen & Ink is an ideal way to sketch down some visual ideas or simply spark your imagination.   | Read more »
Sonic & All-Stars Racing Transformed...
Sonic & All-Stars Racing Transformed Now Free, to Add New Iconic Characters and Elements Posted by Tre Lawrence on April 24th, 2014 [ | Read more »
Soccer Rally 2 Review
Soccer Rally 2 Review By Carter Dotson on April 24th, 2014 Our Rating: :: GOALKEEPINGUniversal App - Designed for iPhone and iPad Soccer Rally 2 is the most serious vehicular soccer game ever created.   | Read more »
Galaxy Conquerors Review
Galaxy Conquerors Review By Jennifer Allen on April 24th, 2014 Our Rating: :: RETRO SHOOTINGUniversal App - Designed for iPhone and iPad Old school shooting is fun but inaccurate in Galaxy Conquerors.   | Read more »
Yomi Review
Yomi Review By Rob Thomas on April 24th, 2014 Our Rating: :: C-C-C-COMBO BREAKERiPad Only App - Designed for the iPad Round One – Fight! No quarters required for this iOS adaptation of a tabletop adaptation of the arcade fighting... | Read more »
Injustice: Gods Among Us Updated with Ne...
Injustice: Gods Among Us Updated with New Characters, Leaderboards, Gear, and Online Multiplayer Posted by Rob Rich on April 24th, 2014 [ | Read more »
Spin It Review
Spin It Review By Jordan Minor on April 24th, 2014 Our Rating: :: SPIN ME RIGHT ROUNDUniversal App - Designed for iPhone and iPad Spin It has a fine puzzle game model, but its execution lacks energy.   | Read more »
Productivity App NoteSuite is Having its...
Productivity App NoteSuite is Having its Biggest Sale Ever, Just for One Week Posted by Rob Rich on April 24th, 2014 [ permalink ] | Read more »
Wayward Souls Review
Wayward Souls Review By Carter Dotson on April 24th, 2014 Our Rating: :: CARRY ON, WAYWARD SONUniversal App - Designed for iPhone and iPad Wayward Souls is a roguelike-inspired action-RPG that sets a high bar for other games to... | Read more »
The Sandbox Gets Update, Receives New Ca...
The Sandbox Gets Update, Receives New Campaign and New Elements Posted by Tre Lawrence on April 24th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »

Price Scanner via MacPrices.net

Strong iPhone Sales Drive Apple Record March...
Apple on Wednesday announced financial results for its fiscal 2014 second quarter ended March 29, 2014. The Company posted quarterly revenue of $45.6 billion and quarterly net profit of $10.2 billion... Read more
Award-Winning NoteSuite Productivity App is $...
Minneapolis based Theory.io has announced an 80-Percent Markdown NoteSuite for iPad. NoteSuite helps users stay organized by capturing their notes, to-dos and documents in one organized place.... Read more
16GB 1st generation iPad mini available for $...
Radio Shack has a select number of refurbished 1st generation 16GB WiFi iPad minis available for $199.99 on their online store. Choose free shipping or free ship-to-store. We expect these to sell out... Read more
13-inch 2.5GHz MacBook Pro on sale for $100 o...
B&H Photo has the 13″ 2.5GHz MacBook Pro on sale for $1099 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
iPad Sales “Lull” A Reality Correction Of Unm...
I have lots of time for Jean-Louis Gassée, the former Apple Computer executive (1981 to 1990) who succeeded Steve Jobs as head of Macintosh development when the latter was dismissed in 1985. Mr.... Read more
Apple Makes OS X Betas Available To All – Wit...
Apple’s OS X Beta Seed Program, which lets you install the latest pre-release builds, try it out, and submit your feedback, is now open to anyone who wants to sign on rather than to developers and... Read more
Apple Releases iOS 7.1.1 Update
The latest iOS 7.1.1 update contains improvements, bug fixes and security updates, including: • Further improvements to Touch ID fingerprint recognition • Fixes a bug that could impact keyboard... Read more
Logitech Announces Thinner, Lighter, More Fle...
Logitech has announced an update to its Ultrathin for iPad Air, iPad mini and iPad mini with Retina display, improving the flexibility and design of its award-winning predecessor with an even thinner... Read more
Logitech Introduces Hinge, Big Bang and Turna...
Logitech has announced expansion of its tablet product line with three new cases – the Logitech Hinge, the Logitech Big Bang and the Logitech Turnaround – each for the iPad Air, iPad mini and iPad... Read more
WaterField’s Rough Rider Leather Messenger Ba...
WaterField Designs have announced the new 15-inch size of their popular Rough Rider leather messenger bag, a vintage-looking bag that combines Old West charm and ruggedness with distinctly modern... Read more

Jobs Board

*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Position Opening at *Apple* - Apple (United...
…customers purchase our products, you're the one who helps them get more out of their new Apple technology. Your day in the Apple Store is filled with a range of Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Inc. Research Data Specialist - Appl...
…of Worldwide Market Research & Intelligence. The team is responsible for conducting Apple branded consumer market research. It is also responsible for analyzing data Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.