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Unix for Mac OS X Users
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Customizing the command prompt


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Unix for Mac OS X Users

with Kevin Skoglund

Video: Customizing the command prompt

In this movie we're going to learn how to customize the Unix command prompt. And we talked about long time ago the prompt is this bit of text right here that occurs before every line, right, to prompt you to enter something. I don't know why, but it's very, very satisfying to customize that to something that you like. Maybe it's because it's the part of Unix that you see most often, but it's really useful to be able to customize that and make it look exactly the way that you want. The way that we're going to do that is with a shell variable. And we saw shell variables in the last movie. The shell variable we want here is PS1. That's for the main command prompt.
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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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Unix for Mac OS X Users
6h 35m Beginner Apr 29, 2011

Viewers: in countries Watching now:

Unix for Mac OS X Users unlocks the powerful capabilities of Unix that underlie Mac OS X, teaching how to use command-line syntax to perform common tasks such as file management, data entry, and text manipulation. The course teaches Unix from the ground up, starting with the basics of the command line and graduating to powerful, advanced tools like grep, sed, and xargs. The course shows how to enter commands in Terminal to create, move, copy, and delete files and folders; change file ownership and permissions; view and stop command and application processes; find and edit data within files; and use command-line shortcuts to speed up workflow. Exercise files accompany the course.

Topics include:
  • Moving around the file system
  • Creating and reading files
  • Copying, moving, renaming, and deleting files and directories
  • Creating hard links and symbolic links
  • Understanding user identity, file ownership, and sudo
  • Setting file permissions with alpha and octal notation
  • Changing the PATH variable
  • Using the command history
  • Directing input and output
  • Configuring the Unix working environment
  • Searching and replacing using grep and regular expressions
  • Manipulating text with tr, sed, and cut
  • Integrating with the Finder, Spotlight, and AppleScript
Subjects:
Developer Web
Software:
Mac OS X Unix
Author:
Kevin Skoglund

Customizing the command prompt

In this movie we're going to learn how to customize the Unix command prompt. And we talked about long time ago the prompt is this bit of text right here that occurs before every line, right, to prompt you to enter something. I don't know why, but it's very, very satisfying to customize that to something that you like. Maybe it's because it's the part of Unix that you see most often, but it's really useful to be able to customize that and make it look exactly the way that you want. The way that we're going to do that is with a shell variable. And we saw shell variables in the last movie. The shell variable we want here is PS1. That's for the main command prompt.

There's also a PS2, 3 and 4. those are for other prompts that occur in other contexts and we don't need to worry about those. PS1 is the one we want. PS1= and then we can make it equal to whatever we want, so -->. It's always a good idea to put a space after it just so that it separates the prompt from what you're about to type. Notice the space that it gave me. We could try it without the space and see the difference. See now when I type it's right up against that. So if you like that, you certainly can do it. I prefer to have the space there. So that's it. You can see that it took effect right- away but like the shell variables that we were setting before, if we close this window and log out, it won't be set anymore.

In order to have shell variables set so that they're there all the time, we need to put those in either our .bash_profile or our .bashrc file. If we define them there, then as soon as we log in, then our prompt will be defined the way we want it. So we're going to do that. We're going to move it over there, but this is a great way to play with it. Just play with it here, get it to something that you like, and then we'll move over to .bashrc and we'll actually plug it in there permanently. So let's try a few more. You can have it be whatever you want. You're going to be What now?, space, and that's what you'll get every time, or you can have it just be something like your username, all right. kevin.

Now that's the string kevin. That's not my username kevin. In order to get the username I have to use some special formatting codes. \u will be for my username, so that's my actual username. The other one was just a string of characters. It could have just as easily been bob. It wouldn't have mattered. \u is actually pulling my username from Unix. Let's look at what these other formatting codes are so that you'll be able to use them when customizing your prompt. So as we just saw there's u for username. We also can use a lowercase s for the current shell that we're in. bash in this case.

There's lower case w and upper W which will show the working directory. The difference is that w shows you the full path to get to the working directory whereas capital W just shows you essentially the name of the folder that you're in, just that current directory only. w is the same thing as if you typed pwd. Then there's \d which will show you the date. There's \D which allows you to then provide curly braces with a format, a string from time format. You can look up with those formatting codes or other places. I've just given you a real simple one to show you the year, the month, and the day.

Then we have four different ones that'll show the time, depending on the format you want. There's capital A, lowercase t, there's the at sign, and then there's the capital T. There's capital H for hostname, lowercase h for just the first part of the hostname. There's exclamation point which will be the history number of this command. If you use your history a lot, that might be useful. And then there's the special dollar sign. If you're logged in as root, that will then display a pound sign; otherwise it's going to display a dollar sign . So essentially it gives you a nice visual cue for whether or not you're logged in as root at the moment.

And then \\ would be a literal backslash, if you want to use the actual backslash character instead of using it for one of these formatting codes. So before we launch into a lot of these let me just show you what the Mac default. The Mac default is the \h:\W \u$, space, and then we close the quotes. So that's the default setting. If you decide oh, you know what, I liked most of that. I just wish it didn't show me the hostname at the beginning. Well then, no problem. You can take that out. Let's try some other ones.

So let's say we have t that'll show us the time. We have capital T was another one, shows the time. Capital A. We have a at sign that we can plug in there. So you see the different versions the time that it'll give you. Let's do a lowercase d for the date. If we want capital D then we need to provide some formatting as well. Capital D and then inside the curly braces we'll use %Y-%m-%d. The percents are the special characters.

These dashes could just as easily be swapped in with something like this if you like that better. So let's just do the dashed version for now. There we go. And you can combine these of course. So if you want that, then you also wanted to have a space followed by a slash. Let's pick the at sign. there you go. So now you get the date and time. Now I just want to show you the difference between the w version. Go up here and let's pick out w, lowercase w. Notice that in my current directory it's just the tilde. If I switch into the unix_files directory into test1, now I get that full path, right? Exactly the same thing as if I did pwd, except it abbreviates it for the fact that I am in my user directory.

So it tries to shorten it when it can, but it does still show me the full path. If I instead put the prompt with a capital W, then now I get just the current directory that I am in. As I move backwards I see just the current directory. So again, you can customize it to be absolutely anything you want. This is actually one of the ones that I find to be most useful. So I am just going to copy that using Command+C and then I will back up into my user directory, nano .bashrc, and then we'll just put that in there. Let's drop it right below all the exports we do here.

We'll do export PS1. Now remember export we need to do to make sure that it's available all the time, so go ahead and make sure you add that. export PS1 and then whatever prompt you decided you liked. Ctrl+X. save it, and then just to make sure that it takes effect, you want to say source .bashrc and that'll read that file then. So now that's my prompt and as I move around we'll just see the current directory that I am in. unix_files. That's the file we'll see. So on your own, play around with those different format codes, come up with a prompt that works well for you, and then put that in your .bashrc file.

Find answers to the most frequently asked questions about Unix for Mac OS X Users.


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Q: The exercise files for the following movies appear to be broken:
07_02_files
07_03_files
07_04_files
07_05_files
08_03_files

Is there something wrong with them?
These exercises include one or more "dot files", whose file names start with a period. These files are normally hidden from view by the Finder.  So that they would show up in the Finder, the period has been removed from the file names. Additionally, "_example" has been added at the end of the file name to make it clear that the file will not work as-is. To make the dot files usable, either:

1) Open the file in a text editor to view its contents. Note that it may not be possible to double-click the file to open it because there is no file extension (such as .txt).
2) Resave the file under a new name (usually by choosing File > Save As), adding a "." to the beginning of the file name and removing "_example" from the end.

OR

1) Copy and rename the file from the Unix command line using the techniques discussed in this course. Rename the file by adding a "." to the start and removing "_example" from the end. Include the "-i" option to prevent overwriting an existing file unexpectedly.
Example:  cp -i ~/Desktop/Exercise\ Files/Chapter_07/07_02_files/bashrc_example ~/.bashrc
 
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