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Patterns
The patterns used by case are the same as those used by pathname expansion. Patterns are terminated with a “)” character. Here are some valid patterns:
Table 31- 1: case Pattern Examples
Pattern Description
Pattern Description
a) Matches if word equals “a”.
[[:alpha:]]) Matches if word is a single alphabetic character.
???) Matches if word is exactly three characters long.
*.txt) Matches if word ends with the characters “.txt”.
*) Matches any value of word. It is good practice to include this as the last pattern in a case command, to catch any values of word that did not match a previous pattern; that is, to catch any possible invalid values.
Here is an example of patterns at work:
#!/bin/bash
read -p "enter word > " case $REPLY in
[[:alpha:]]) echo "is a single alphabetic character." ;; [ABC][0-9]) echo "is A, B, or C followed by a digit." ;;
???) echo "is three characters long." ;;
*.txt) echo "is a word ending in '.txt'" ;;
*) echo "is something else." ;; esac
#!/bin/bash
read -p "enter word > " case $REPLY in
[[:alpha:]]) echo "is a single alphabetic character." ;; [ABC][0-9]) echo "is A, B, or C followed by a digit." ;;
???) echo "is three characters long." ;;
*.txt) echo "is a word ending in '.txt'" ;;
*) echo "is something else." ;; esac
It is also possible to combine multiple patterns using the vertical bar character as a sepa- rator. This creates an “or” conditional pattern. This is useful for such things as handling both upper- and lowercase characters. For example:
#!/bin/bash
# case-menu: a menu driven system information program clear
echo "
Please Select:
A. Display System Information
B. Display Disk Space
C. Display Home Space Utilization
Q. Quit "
read -p "Enter selection [A, B, C or Q] > "
case $REPLY in
q|Q) echo "Program terminated." exit
;;
a|A) echo "Hostname: $HOSTNAME" uptime
;;
b|B) df -h
;;
c|C) if [[ $(id -u) -eq 0 ]]; then
echo "Home Space Utilization (All Users)" du -sh /home/*
else
echo "Home Space Utilization ($USER)" du -sh $HOME
fi
#!/bin/bash
# case-menu: a menu driven system information program clear
echo "
Please Select:
A. Display System Information
B. Display Disk Space
C. Display Home Space Utilization
Q. Quit "
read -p "Enter selection [A, B, C or Q] > "
case $REPLY in
q|Q) echo "Program terminated." exit
;;
a|A) echo "Hostname: $HOSTNAME" uptime
;;
b|B) df -h
;;
c|C) if [[ $(id -u) -eq 0 ]]; then
echo "Home Space Utilization (All Users)" du -sh /home/*
else
echo "Home Space Utilization ($USER)" du -sh $HOME
fi
;;
*) echo "Invalid entry" >&2 exit 1
;;
esac
;;
*) echo "Invalid entry" >&2 exit 1
;;
esac
Here, we modify the case-menu program to use letters instead of digits for menu selec- tion. Notice how the new patterns allow for entry of both upper- and lowercase letters.