> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Parameter Part Two
> Explores advanced parameter expansion techniques using wildcards for flexible string manipulation in Linux, focusing on file paths and extensions.
In Part One, we covered basic parameter‐expansion techniques for stripping fixed prefixes or suffixes. Here, we’ll explore more flexible patterns using wildcards to handle arbitrary extensions, path segments, or words in a string.
## Removing Fixed Prefixes and Suffixes
Often in Linux you work with file paths and extensions:
| Component | Example 1 | Example 2 | Example 3 |
| --------- | -------------------- | -------------------- | ----------- |
| Prefix | `/home/my_username/` | `/home/my_username/` | `/usr/bin/` |
| Name | `text_file` | `text_file2` | `app.py` |
| Suffix | `.txt` | `.txt` | `.py` |
A fixed‐suffix removal like `${var%.txt}` only matches when the filename actually ends in `.txt`:
```bash theme={null}
$ var="/home/my_username/text_file.txt"
$ echo "${var%.txt}"
/home/my_username/text_file
$ var="/home/my_username/text_file2.txt"
$ echo "${var%.txt}"
/home/my_username/text_file2
$ var="/usr/bin/app.py"
$ echo "${var%.txt}"
/usr/bin/app.py
```
Using `${var%.txt}` leaves `.py` files untouched. For arbitrary extensions or dynamic patterns, you’ll need wildcards.
***
## Using Wildcards for General Cases
By introducing `*` in the pattern, you can remove everything up to or after a delimiter (space, slash, dot, etc.).
### Strip the First Word
For a space-separated string, `${var#* }` removes the shortest match from the front (everything up to the first space):
```bash theme={null}
export position1="Senior Cloud Architect"
export position2="Senior DevOps Engineer"
export position3="Associate Frontend Engineer"
export position4="Junior Software Developer"
echo "${position1#* }" # Cloud Architect
echo "${position2#* }" # DevOps Engineer
echo "${position3#* }" # Frontend Engineer
echo "${position4#* }" # Software Developer
```
### Strip the Last Word
Using `${var% *}` removes the shortest match from the end (from the last space onward):
```bash theme={null}
echo "${position1% *}" # Senior Cloud
echo "${position2% *}" # Senior DevOps
echo "${position3% *}" # Associate Frontend
echo "${position4% *}" # Junior Software
```
Always pair `*` with a literal character (e.g., space or slash). A pattern like `${var%*}` matches the entire string, returning an empty result.
***
## Handling Unix‐Style Filenames
Consider two variables:
```bash theme={null}
my_text_file="/home/my_username/text_file.txt"
my_python_file="/usr/bin/app.py"
```
* **Prefix**: directory path
* **Name**: file name
* **Suffix**: extension
### Remove All Directory Components
* `${var#*/}` strips up to the *first* slash
* `${var##*/}` strips up to the *last* slash (longest‐prefix removal)
```bash theme={null}
echo "${my_text_file#*/}" # home/my_username/text_file.txt
echo "${my_python_file#*/}" # usr/bin/app.py
echo "${my_text_file##*/}" # text_file.txt
echo "${my_python_file##*/}" # app.py
```
### Strip File Extension
Use shortest‐suffix (`%`) or longest‐suffix (`%%`). With a single dot, both behave identically:
```bash theme={null}
echo "${my_text_file%.*}" # /home/my_username/text_file
echo "${my_text_file%%.*}" # /home/my_username/text_file
echo "${my_python_file%.*}" # /usr/bin/app
echo "${my_python_file%%.*}" # /usr/bin/app
```
***
## Choosing the Right Operator
| Operator | Description | Example |
| ----------- | ---------------------------- | -------------------------------- |
| `${var#…}` | Remove shortest prefix match | Strip up to first delimiter |
| `${var##…}` | Remove longest prefix match | Strip up to last delimiter |
| `${var%…}` | Remove shortest suffix match | Remove first occurrence from end |
| `${var%%…}` | Remove longest suffix match | Remove all occurrences from end |
* Use **shortest‐suffix** (`%`) for extensions.
* Use **longest‐prefix** (`##`) for directory paths.
With these four operators, you can tailor string manipulations to filenames, paths, or any delimited data.
***
## Links and References
* [Bash Parameter Expansion](https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html)
* [Kubernetes Basics](https://kubernetes.io/docs/concepts/overview/what-is-kubernetes/)
* [Docker Hub](https://hub.docker.com/)