Update 003-the-cat-tac-command.md (bobbyiliev#222)

Changed command focused from only txt file to any kind of file.

Author: ashutosh321607

ebook/en/content/003-the-cat-tac-command.md

@@ -24,13 +24,13 @@ cat file1 file2 ...
 3. To create a file with the cat command:
 
 ```
-cat > filename
+cat > file_name
 ```
 
 4. To display all files in current directory with the same filetype:
 
 ```
-cat *.txt
+cat *.<filetype>
 ```
 
 5. To display the content of all the files in current directory:
@@ -42,7 +42,7 @@ cat *
 6. To put the output of a given file into another file:
 
 ```
-cat oldfile > newfile
+cat old_file_name > new_file_name
 ```
 7. Use cat command with `more` and `less` options:
 
@@ -51,22 +51,22 @@ cat filename | more
 cat filename | less
 ```
 
-8. Append the contents of file1.txt to file2.txt:
+8. Append the contents of file1 to file2:
 
 ```
-cat file1.txt >> file2.txt
+cat file1 >> file2
 ```
 
 9. To concatenate two files together in a new file:
 
 ```
-cat file1.txt file2.txt merge.txt
+cat file1_name file2_name merge_file_name
 ```
 
 10. Some implementations of cat, with option -n, it's possible to show line numbers:
 
 ```
-cat -n file1.txt file2.txt > newnumberedfile.txt
+cat -n file1_name file2_name > new_numbered_file_name
 ```
 
 
@@ -114,15 +114,15 @@ tac <specified_file_name>
 2. This option attaches the separator before instead of after.
 
 ```
-tac -b concat.txt tacexample.txt
+tac -b concat_file_name tac_example_file_name
 ```
 3. This option will interpret the separator as a regular expression.
 ```
-tac -r concat.txt tacexample.txt
+tac -r concat_file_name tac_example_file_name
 ```
 4. This option uses STRING as the separator instead of newline.
 ```
-tac -s concat.txt tacexample.txt
+tac -s concat_file_name tac_example_file_name
 ```
 
 5. This option will display the help text and exit.