Join Kevin Skoglund for an in-depth discussion in this video The PATH variable, part of Unix for Mac OS X Users.
In the last movie, we saw how commands and programs are really just files that…are being executed, and we saw that we type echo 'Hello world' that what it's…actually doing is executing a file that is located in bin/echo.…I write the argument.…Those are doing exact same thing.…This is just a shortcut for finding this file and executing it.…So how does Unix do that?…How does Unix know to find echo in this location or to put it another way,…if I create another file named echo, how does Unix know not to use that one…instead, or what if I wanted it to use that one instead?…How would I go about doing that?…Well, the way that Unix manages all of this is with a variable called PATH.…
$PATH will show you the current value of your path and the path is always a…colon-separated list of file paths and this is the list that Unix will use when…trying to locate commands to execute.…The early entries take precedence over the later ones.…So what it does is it starts at the left.…When we type echo, it says, "Oh! I'll look in user bin.…
- 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
Skill Level Beginner
Q: The exercise files for the following movies appear to be broken:
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.
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
The instructor uses the UNIX program 'units' to convert 72° Fahrenheit to degrees Celsius. The returned value of 40 is incorrect. The correct result should be 22°C. What's the reason for this discrepancy?
The problem is that units does the 5/9 calculation but does not have the ability to subtract 32. So you'll need to subtract (or add) the 32 degrees yourself.
1. Introduction to Unix
2. Filesystem Basics
3. Working with Files and Directories
4. Ownership and Permissions
5. Commands and Programs
6. Directing Input and Output
7. Configuring Your Working Environment
8. Unix Power Tools
9. Useful Mac-Only Commands and Techniques
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