Update bash-extracting_from_files.md

docs/pages/bash/bash-extracting_from_files.md

@@ -191,7 +191,20 @@ You can redirect a result and store it in a file thanks to the `>` redirection:
 ## Replacing patterns (sed)
 
 
+!!! question "Using the sed command, convert CSV file into a tabular file in a new file called `nat2021.tsv`"
 
 
+??? example "Click to show the solution"  
+    ```bash
+    # command
+    sed "s/;/\t/g" nat2021.csv > nat2021.tsv
+    ```
 
+!!! question "In the tabular file, replace the information 1/2 by F/M"
 
+??? example "Click to show the solution"  
+    ```bash
+    # command
+    sed -i "s/^1/M/g" nat2021.tsv
+    sed -i "s/^2/F/g" nat2021.tsv
+    ```
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