comparing files

Juanita is a highly experienced and competent RHEL Sysadmin at Red Hat. She want compare 3 files and find ALL developers who are in all 3 files: 

1. kubernetes_instructors.txt
2. linux_instructors.txt
3. mariadb_intructors.txt

She wants to add all developers in all 3 files to a new file called have_kubernetes_linux_and_mariadb_expertise.txt so that she can email them and have them start developing lesson plans for an upcoming Kubernetes-Linux-MariaDB Intregration Training Week.

Please list and explain all comm commands that Juanita will need to issue to complete project.

Juanita can use the comm command to find the lines that are common in all three files and create a new file with their names. Here are the commands she will need to issue:

1. Change the current working directory to the directory where the three files are located.
   • cd /path/to/files
2. Use the comm command to find the lines that are common in all three files.
   • sudo comm -12 <(sort kubernetes_instructors.txt) <(sort linux_instructors.txt) <(sort mariadb_instructors.txt) > common_instructors.txt

   • The comm command compares two files line by line and outputs the lines that are common to both files. We need to run the comm command three times to compare all three files.

     The -12 option suppresses lines that are unique to the first or second file, and only shows the common lines in both files. The <() syntax is a process substitution that allows us to sort the files before passing them to the comm command.

     The > operator redirects the output to a file called common_instructors.txt.

3. Create a new file called have_kubernetes_linux_and_mariadb_expertise.txt and copy the contents of common_instructors.txt to it.
   • sudo touch have_kubernetes_linux_and_mariadb_expertise.txt
   • sudo cp common_instructors.txt have_kubernetes_linux_and_mariadb_expertise.txt
4. Email the instructors whose names are in the new file using the mail command or any other preferred email client.

Overall, the commands that Juanita will need to issue are: 

• • cd /path/to/files
  • sudo comm -12 <(sort kubernetes_instructors.txt) <(sort linux_instructors.txt) <(sort mariadb_instructors.txt) > common_instructors.txt
  • sudo touch have_kubernetes_linux_and_mariadb_expertise.txt
  • sudo cp common_instructors.txt have_kubernetes_linux_and_mariadb_expertise.txt