To specify an action when a word matches the pattern:
cat diary #!/bin/sh today=`date +%m/%d` (presents the date in the format 01/31) case $today in 07/18) echo "Aonoch Mhor" ;; 07/21) echo "Ben Wyvis" ;; 08/02) echo "Buicheille Etive Mhor" ;; 08/03) echo "Slioch" ;; *) echo "Wet..low level today" esac date +%m/%d 07/18 diary Aonoch Mhor
The value for the word $today is generated by the date command. This is then compared with various patterns so that the appropriate commands are executed.
Note the use of the pattern *, this can be used to specify default patterns as the * character is the shell wildcard character.