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Stopping processes

From: Unix for Mac OS X Users

Video: Stopping processes

Over the course of the last two movies we've been looking at how we can view and monitor the different processes that are running in Unix. In this movie I want us to see how we can stop processes. Now, the number one best way to stop a process is with Ctrl+C. That assumes that you're running the process inside your Terminal window. You started it. It's just taking too long or maybe you changed your mind in the middle of it. Ctrl+C tells Unix, hey! Stop that process, interrupt it, let's go back to the command line. So that's the best thing, but sometimes we can't use that. Sometimes there are processes that are running in the background, or maybe there's a process that we did have control of but somehow we've lost control.

Stopping processes

Over the course of the last two movies we've been looking at how we can view and monitor the different processes that are running in Unix. In this movie I want us to see how we can stop processes. Now, the number one best way to stop a process is with Ctrl+C. That assumes that you're running the process inside your Terminal window. You started it. It's just taking too long or maybe you changed your mind in the middle of it. Ctrl+C tells Unix, hey! Stop that process, interrupt it, let's go back to the command line. So that's the best thing, but sometimes we can't use that. Sometimes there are processes that are running in the background, or maybe there's a process that we did have control of but somehow we've lost control.

So we can still see it, we can see it's running there, and we really wish it would go away. Well, to do that, we use the kill command. In order to show you how we would do it, let's do ps aux. We see a listing there and you will see I have a listing on here for s000 bash. That's my current bash program. Now I am going to open up a new window. Essentially what I want here is a process that I am not afraid to kill off, because I don't have an errant process running right now and I don't want to use sort of advanced tricks to get one running. Instead, I am just going to create this new Terminal here.

Now when I do ps aux you'll see that I see another bash here and this bash is owned by 0001. Let's clear the screen just so we can see it nice and well. Here is bash down here and if we scroll up here, it should be this other bash up here. Now notice 000 is the one that I am on. That's the one I don't want to get rid of. The one I want to get rid of is 001. That's the other window that's going on and that's the process I am going to kill. I am going to forcibly just stop that bash from running.

What I need is the process ID. That's how we tell Unix which process we want. Every single process has a unique ID, so it's the way that we can reference it. What we use is kill 1837. That's the process ID. We have killed it, except that we haven't. Some processes can't be killed by using kill on its own like this. So always try kill first. It'll do its best to kill it off. But there are cases where it'll say, you know what, I think you probably don't want to do that. This is one of those cases, because it's running bash in a Terminal window.

So it says, you know what, I could kill that off but I think that's probably not a great idea. So it didn't do it. Let's just take a look here. ps aux, I will clear the screen, just so we can see it is still running. Right here it is 001, bash, same process ID. But if we pass it the -9 option, that says, yeah! I know better than you. It means really, really, really kill this thing off. Forcibly kill it. So kill -9 and then the process ID number. Now, I killed it off. Let's take ps aux again. Take a look.

Notice that it's not there. The only bash that I have is 000 and come over here to the other Terminal and look, process completed. The process is done. If I hit anything, I don't get anything in that window anymore. I killed off that process. But you can do this anytime you've got a process that's taking up tons of memory, tons of CPU usage, something you don't have control over. Obviously you want to be careful. A lot of these processes your system needs. You don't want to just start killing off processes willy-nilly. But it is a technique if there is a process that you know needs to be killed. This is how you would do it.

First, try kill and then kill with the - 9 option as well.

Show transcript

This video is part of

Image for Unix for Mac OS X Users
Unix for Mac OS X Users

82 video lessons · 27833 viewers

Kevin Skoglund
Author

 
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  1. 3m 57s
    1. Introduction
      1m 14s
    2. Using the exercise files
      2m 43s
  2. 32m 2s
    1. What is Unix?
      7m 27s
    2. The terminal application
      4m 23s
    3. Logging in and using the command prompt
      5m 19s
    4. Command structure
      5m 22s
    5. Kernel and shells
      5m 25s
    6. Unix manual pages
      4m 6s
  3. 15m 58s
    1. The working directory
      2m 49s
    2. Listing files and directories
      3m 59s
    3. Moving around the filesystem
      4m 58s
    4. Filesystem organization
      4m 12s
  4. 1h 4m
    1. Naming files
      5m 41s
    2. Creating files
      2m 19s
    3. Unix text editors
      6m 39s
    4. Reading files
      5m 35s
    5. Reading portions of files
      3m 27s
    6. Creating directories
      2m 40s
    7. Moving and renaming files and directories
      8m 32s
    8. Copying files and directories
      3m 7s
    9. Deleting files and directories
      3m 38s
    10. Finder aliases in Unix
      4m 10s
    11. Hard links
      5m 30s
    12. Symbolic links
      6m 36s
    13. Searching for files and directories
      6m 32s
  5. 34m 58s
    1. Who am I?
      4m 3s
    2. Unix groups
      1m 52s
    3. File and directory ownership
      6m 41s
    4. File and directory permissions
      4m 27s
    5. Setting permissions using alpha notation
      6m 49s
    6. Setting permissions using octal notation
      3m 49s
    7. The root user
      1m 57s
    8. sudo and sudoers
      5m 20s
  6. 52m 34s
    1. Command basics
      4m 4s
    2. The PATH variable
      4m 13s
    3. System information commands
      3m 40s
    4. Disk information commands
      6m 8s
    5. Viewing processes
      5m 0s
    6. Monitoring processes
      3m 36s
    7. Stopping processes
      3m 19s
    8. Text file helpers
      6m 50s
    9. Utility programs
      7m 28s
    10. Using the command history
      8m 16s
  7. 20m 39s
    1. Standard input and standard output
      1m 24s
    2. Directing output to a file
      4m 13s
    3. Appending to a file
      2m 44s
    4. Directing input from a file
      5m 28s
    5. Piping output to input
      4m 40s
    6. Suppressing output
      2m 10s
  8. 41m 28s
    1. Profile, login, and resource files
      9m 11s
    2. Setting command aliases
      6m 59s
    3. Setting and exporting environment variables
      4m 54s
    4. Setting the PATH variable
      6m 10s
    5. Configuring history with variables
      6m 17s
    6. Customizing the command prompt
      6m 5s
    7. Logout file
      1m 52s
  9. 1h 25m
    1. grep: Searching for matching expressions
      5m 21s
    2. grep: Multiple files, other input
      4m 28s
    3. grep: Coloring matched text
      2m 57s
    4. Introduction to regular expressions
      3m 22s
    5. Regular expressions: Basic syntax
      3m 19s
    6. Using regular expressions with grep
      5m 20s
    7. tr: Translating characters
      8m 17s
    8. tr: Deleting and squeezing characters
      5m 30s
    9. sed: Stream editor
      7m 45s
    10. sed: Regular expressions and back-references
      7m 8s
    11. cut: Cutting select text portions
      7m 42s
    12. diff: Comparing files
      4m 35s
    13. diff: Alternative formats
      4m 30s
    14. xargs: Passing argument lists to commands
      7m 25s
    15. xargs: Usage examples
      7m 59s
  10. 42m 25s
    1. Finder integration
      4m 45s
    2. Clipboard integration
      5m 5s
    3. Screen capture
      3m 42s
    4. Shut down, reboot, and sleep
      3m 34s
    5. Text to speech
      2m 36s
    6. Spotlight integration: Searching metadata
      3m 41s
    7. Spotlight integration: Metadata attributes
      4m 24s
    8. Using AppleScript
      5m 23s
    9. System configurations: Viewing and setting
      5m 51s
    10. System configurations: Examples
      3m 24s
  11. 1m 26s
    1. Conclusion
      1m 26s

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