Join Kevin Skoglund for an in-depth discussion in this video tr: Translating characters, part of Unix for Mac OS X Users.
In this movie, we're going to take a look at another simple but powerful…Unix tool called TR.…TR is short for Translate and what it does is it copies from the input it…receives to output, but with the substitution of selected characters, according…to translation rules that we give it.…So at its simplest we would have echo a, b, c, and we'll pipe that in to tr, and…the first argument of tr is going to be the thing we want to search for. Our search string.…So we're going to search for all of the commas, and the second argument will be…the replacement string.…
So we'll replace it all with dashes. So as you might guess, it takes all the…commas and it translates them into being dashes.…Now this is a totally valid use.…But translating one character to one character doesn't really reveal how TR works.…So let's try another better example.…Let's say we have echo and for this string let's use the numbers 1 to 6, so…you can just peck away through your keyboard, just pick a random set of…numbers, but not going any higher than 6. And then we're going to pipe that…
- 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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