Join Kevin Skoglund for an in-depth discussion in this video Reading portions of files, part of Unix for Mac OS X Users.
In this movie, we'll look at two other useful commands for reading files.…They are head and tail.…The difference is with both of these commands, they will read just a portion of the file.…head displays the lines from the beginning of the file. This is useful for just…peeking at the start of the file, let's say viewing the first ten lines.…tail does the same thing but in reverse.…It displays lines from the end of a file.…This comes in very handy, when you want to look at files like access logs or…error logs where the latest entries in the file will be added to the end.…So for example, you can view the tail of a web server's access log to see the…most recent requests made to the web server.…
tail also has a very useful option, the f option which allows us to follow the file.…It reads the tail of the file normally, but then instead of exiting back to the…command prompt, it will watch for changes to the file.…Whenever a new line is added, it will show us that line. We are following the…file waiting for updates.…
- 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
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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