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.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Carbon Copy Cloner 4.1.18 - Easy-to-use...
Carbon Copy Cloner backups are better than ordinary backups. Suppose the unthinkable happens while you're under deadline to finish a project: your Mac is unresponsive and all you hear is an ominous,... Read more
Hopper Disassembler 4.2.14- - Binary dis...
Hopper Disassembler is a binary disassembler, decompiler, and debugger for 32- and 64-bit executables. It will let you disassemble any binary you want, and provide you all the information about its... Read more
BetterTouchTool 2.291 - Customize Multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
Sound Studio 4.8.11 - Robust audio recor...
Sound Studio lets you easily record and professionally edit audio on your Mac. Easily rip vinyls and digitize cassette tapes, or record lectures and voice memos. Prepare for live shows with live... Read more
Sound Studio 4.8.11 - Robust audio recor...
Sound Studio lets you easily record and professionally edit audio on your Mac. Easily rip vinyls and digitize cassette tapes, or record lectures and voice memos. Prepare for live shows with live... Read more
BetterTouchTool 2.291 - Customize Multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
Carbon Copy Cloner 4.1.18 - Easy-to-use...
Carbon Copy Cloner backups are better than ordinary backups. Suppose the unthinkable happens while you're under deadline to finish a project: your Mac is unresponsive and all you hear is an ominous,... Read more
Hopper Disassembler 4.2.14- - Binary dis...
Hopper Disassembler is a binary disassembler, decompiler, and debugger for 32- and 64-bit executables. It will let you disassemble any binary you want, and provide you all the information about its... Read more
VOX 2.8.30 - Music player that supports...
VOX just sounds better! The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features and support for all audio formats you should ever need.... Read more
Default Folder X 5.1.6b3 - Enhances Open...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click on... Read more

The best 2v2 card combos in Clash Royale
2v2 is making it's grand return toClash Royalequite soon. 2v2 has quickly become one of the game's most popular gameplay modes, though they still have yet to make it a permanent fixture in the game. 2v2 is exciting and adds some new flavor to... | Read more »
The best games we played this week - Aug...
Another busy week has come to a close. We played a lot of excellent games this week and now it's time to look back and reflect on some our favorites. Here are our picks for the week of August 18. [Read more] | Read more »
War Wings beginner's guide - how to...
War Wings is the newest project from well-established game maker Miniclip. It's a World War II aerial dogfighting game with loads of different airplane models to unlock and battle. The game offers plenty of single player and multiplayer action. We... | Read more »
How to win every 2v2 battle in Clash Roy...
2v2 is coming back to Clash Royale in a big way. Although it's only been available for temporary periods of time, 2v2 has seen a hugely positive fan response, with players clamoring for more team-based gameplay. Soon we'll get yet another taste of... | Read more »
Roll to Win with Game of Dice’s new upda...
Joycity’s hit Game of Dice gets a big new update this week, introducing new maps, mechanics, and even costumes. The update sets players loose on an exciting new map, The Cursed Tower, that allows folks to use special Runes mid-match. If you feel... | Read more »
Bottom of the 9th (Games)
Bottom of the 9th 1.0.1 Device: iOS iPhone Category: Games Price: $4.99, Version: 1.0.1 (iTunes) Description: Play the most exciting moment of baseball in this fast-paced dice and card game! | Read more »
The best apps for viewing the solar ecli...
If you somehow missed the news, many parts of the United States will be witness to a total solar eclipse on August 21 for the first time in over 90 years. It'll be possible to see the eclipse in at least some capacity throughout the continental U... | Read more »
The 5 best mobile survival games
Games like ARK: Survival Evolved and Conan Exiles have taken the world of gaming by storm. The market is now flooded with hardcore survival games that send players off into the game's world with nothing but maybe the clothes on their back. Never... | Read more »
Portal Walk (Games)
Portal Walk 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Portal Walk is adventure and relaxing platform game about Eugene. Eugene stuck between worlds and trying to find way back home.... | Read more »
Technobabylon (Games)
Technobabylon 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: City of Newton, 2087. Genetic engineering is the norm, the addictive Trance has replaced almost any need for human interaction,... | Read more »

Price Scanner via MacPrices.net

Weekend sale: 13-inch MacBook Pros for up to...
Amazon has new 2017 13″ MacBook Pros on sale today for up to $200 off MSRP, each including free shipping: – 13″ 3.1GHz/256GB Space Gray MacBook Pro (MPXV2LL/A): $1599.99 $200 off MSRP – 13″ 3.1GHz/... Read more
Back To School With The Edge Desk All-in-one...
Back to school is just around the corner, and the ergonomically correct Edge Desk all-in-one portable kneeling desk is ideal for students living in dorms and small apartments, Edge Desk features:... Read more
Norton Core Secure Wi-Fi Router Now Available...
First introduced at the 2017 Consumer Electronics Show (CES), Norton Core, a secure, high-performance Wi-Fi router, fundamentally changed the concept of Wi-Fi routers by making security the primary... Read more
ViewSonic Adds New 27-inch 4K UHD Monitor to...
ViewSonic Corp. has introduced the VP2785-4K, a 27-inch 4K UHD (3840×2160) monitor that delivers precise and consistent color representation and performance to ensure incredible image quality. Built... Read more
Apple now offering Certified Refurbished 2017...
Apple is now offering Certified Refurbished 2017 27″ iMacs for up to $350 off original MSRP. Apple’s one-year warranty is standard, and shipping is free. The following models are available: – 27″ 3.... Read more
13-inch 2.3GHz MacBook Pros on sale for $100...
Amazon has the new 2017 13″ 2.3GHz MacBook Pros on sale today for $100 off MSRP, each including free shipping: – 13″ 2.3GHz/128GB Space Gray MacBook Pro (MPXQ2LL/A): $1199.99 $100 off MSRP – 13″ 2.... Read more
Clearance 2016 13-inch MacBook Airs available...
B&H Photo has clearance 2016 13″ MacBook Airs available for up to $200 off original MSRP. Shipping is free, and B&H charges NY & NJ sales tax only: – 13″ 1.6GHz/128GB MacBook Air (MMGF2LL... Read more
Clearance 21-inch and 27-inch iMacs available...
B&H Photo has clearance 21″ and 27″ Apple iMacs available for up to $500 off original MSRP, each including free shipping plus NY & NJ sales tax only: – 27″ 3.3GHz iMac 5K: $1799 $500 off... Read more
New iOS 11 Productivity Features Welcome But...
The iOS community is in late summer holding mode awaiting the September arrival of the iPhone 8 and iOS 11. iOS 11 public betas have been available for months — number six was released this week —... Read more
Samsung Electronics Launches New Portable SSD...
Samsung Electronics America, Inc. has announced the launch of Samsung Portable SSD T5 – its newest portable solid state drive (PSSD) that raises the bar for the performance of external memory... Read more

Jobs Board

Development Operations and Site Reliability E...
Development Operations and Site Reliability Engineer, Apple Payment Gateway Job Number: 57572631 Santa Clara Valley, California, United States Posted: Jul. 27, 2017 Read more
Frameworks Engineering Manager, *Apple* Wat...
Frameworks Engineering Manager, Apple Watch Job Number: 41632321 Santa Clara Valley, California, United States Posted: Jun. 15, 2017 Weekly Hours: 40.00 Job Summary Read more
Map Quality Analyst Lead, *Apple* Maps Eval...
…a team of subject matter experts measuring the quality of a range of Apple Maps algorithms, such as Map search, recommendations, and routing. Our group works with Read more
Business Development Manager, *Apple* Pay -...
Job Summary Apple Pay is seeking an experienced Business Development professional to join the Apple Pay team to develop partnerships and strategic alliances with Read more
Information Systems Engineer, *Apple* Retai...
Job Summary Do you have a passion for the technology and systems that make Apple amazing? Are you interested in joining IS&T Retail on what they do best? This is an Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.