if list; then list; [ elif list; then list; ] ... [ else list; ] fi
       The  if list is executed.  If its exit status is zero, the then list is executed.  Otherwise, each
       elif list is executed in turn, and if its exit status is zero,  the  corresponding  then  list  is
       executed  and  the command completes.  Otherwise, the else list is executed, if present.  The exit
       status is the exit status of the last command executed, or zero if no condition tested true.

check file types and compare values

-s FILE
       FILE exists and has a size greater than zero

list contents of directory

-l     List  in  long  format,  giving  mode (see below), file system type (e.g., for devices, the # code
       letter that names it; see intro(3)), the instance or  subdevice  number,  owner,  group,  size  in
       bytes, and time of last modification for each file.

display a line of text

Echo the STRING(s) to standard output.

cause the shell to exit