fix: Improve grep command to filter files ending with .txt (#7627)

src/data/roadmaps/linux/content/104-text-processing/109-pipe.md

@@ -5,11 +5,11 @@ The pipe (`|`) is a powerful feature in Linux used to connect two or more comman
 Here is a simple example of piping two commands, `ls` and `grep`, to list all the text files in the current directory:
 
 ```bash
-ls | grep .txt
+ls | grep '\.txt$'
 ```
 
-In this example, `ls` lists the files in the current directory and `grep .txt` filters out any files that don't end with `.txt`. The pipe command, `|`, takes the output from `ls` and uses it as the input to `grep .txt`. The output of the entire command is the list of text files in the current directory.
+In this example, `ls` lists the files in the current directory and `grep '\.txt$'` filters out any files that don't end with `.txt`. The pipe command, `|`, takes the output from `ls` and uses it as the input to `grep '\.txt$'`. The output of the entire command is the list of text files in the current directory.
 
 Visit the following resources to learn more:
 
-- [@article@Piping and Redirection](https://ryanstutorials.net/linuxtutorial/piping.php#piping)
+- [@article@Piping and Redirection](https://ryanstutorials.net/linuxtutorial/piping.php#piping)