Mastering Linux Command Line

Wildcards in Linux Commands

Linux commands allow for the use of wildcards to simplify tasks and match patterns effectively.

Wildcard *: Matches zero or more characters.

$ ls bear*

bears bears7 bears_chicago

$ ls *bear*

bears bears7 bears_chicago polarbears

Wildcard ?: Matches exactly one character.

$ ls bears?

bears7

Special Keys for Efficiency

Tab Key: Enables command auto-completion, saving time and reducing errors.
Arrow Keys:
- Move horizontally to edit commands.
- Navigate vertically through the command history.

Command Line Editing with Ctrl and ESC

Ctrl-C: Abort the current process and return to the prompt.
Ctrl-a: Move to the beginning of the line.
Ctrl-e: Move to the end of the line.
ESC Key: Often used to exit a stuck process or editing mode.

Identifying File Types with file

The file command helps determine file types such as text, executable, PDF, or directories.

$ file read-write.txt

$ file world.exe

$ file examples

$ file Linux_slides.pdf

Viewing and Printing Text: `cat` and `echo`

cat: Displays file contents.

$ cat bears

$ cat bears7

$ cat bears bears7

echo: Outputs text to the terminal or writes it to a file.

$ echo ‘Hello World!’

$ echo “Welcome, $USER” > welcome.txt

$ echo “Welcome, $USER” > welcome.txt

Redirect Output (>): Overwrites existing file content.

$ echo ‘Hi there!’ > greeting.txt

$ cat bears > teddybears

Append Output (>>): Adds content to an existing file.

$ echo ‘Hi yourself!’ >> greeting.txt

$ cat bears >> greeting.txt

Exercise: Using `cat` and `echo`

View file contents using cat:

$ cat lions

$ cat tigers

$ cat bears

Combine multiple files into one:

$ cat lions tigers > animals

$ cat bears >> animals

$ cat animals

Use echo to create and modify files:

$ echo ‘My name is Chris’ > myname.txt

$ echo “Hello $USER” >> myname.txt

$ cat myname.txt

Conclusion

Mastering these fundamental Linux commands and features enables efficient navigation, file management, and productivity on the command line. Whether you’re redirecting output, using wildcards, or understanding file types, these tips ensure a smooth Linux experience.

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