Shell Programming and Scripting

#!/usr/bin/ksh
date=$((05 | 06 | 07))
CURRDATE=$(date +%d)
if [[ "$date" = "$CURRDATE" ]]
        then
                echo true
        else
                echo false
fi

if [[ "$CURRDATE" = @(05|06|07) ]]

#!/usr/bin/ksh
date=@(05|06|07)
CURRDATE=$(date +%d)
if [[ "$CURRDATE" = $date ]]
        then
                echo true
        else
                echo false
fi

File Name Generation

Following substitution, each command word  is scanned for the characters *, ?, and [
unless the -f option has been set. 
If one of these characters appears then the word is regarded as a pattern.
The word is replaced with lexicographically sorted file names that match the pattern.
If no file name is found that matches the pattern, then the word is left unchanged. 
When a pattern  is used for file name generation, the character . at the start of a file name
or immediately following a /, as well as the character / itself, must be matched explicitly. 
In other instances of pattern matching the / and . are not treated specially. 

*   Matches any string, including the null string. 
?   Matches any single character. 
[  . . .  ]   Matches any one of the enclosed characters. A pair of characters separated
by - matches any character lexically between the pair, inclusive.
If the first character following the opening "[  " is a "!  " then any character not enclosed
 is matched. 
A - can be included in the character set by putting it as the first or last character. 
A pattern-list is a list of one or more patterns separated from each other with a |.
Composite patterns can be formed with one or more of the following: 

?(pattern-list )   Optionally matches any one of the given patterns. 
*(pattern-list )   Matches zero or more occurrences of the given patterns. 
+(pattern-list )   Matches one or more occurrences of the given patterns. 
@(pattern-list )   Matches exactly one of the given patterns. 
!(pattern-list )   Matches anything, except one of the given patterns.