Learn Linux Shell Scripting - Fundamentals of Bash 4.4

A recap on if-then-else 

If-then-else logic does almost exactly what the name implies: if something-is-the-case, then do-something or else do-something-else. In practice, this could be if the disk is full, then delete some files or else report that the disk space looks great. In a script, this could look something like this:

reader@ubuntu:~/scripts/chapter_09$ cat if-then-else-proper.sh #!/bin/bash###################################### Author: Sebastiaan Tammer# Version: v1.0.0# Date: 2018-09-30# Description: Use the if-then-else construct, now properly.# Usage: ./if-then-else-proper.sh file-name#####################################file_name=$1# Check if the file exists.if [[ -f ${file_name} ]]; then  cat ${file_name} # Print the file content. ...