>Hi all!
>I have this while loop in my script:
>while (($type ne "Windows") || ($type ne "Linux")) {
>print "Enter TYPE of server to build. Linux or Windoze [linux, windows]:\n";
>$type = <STDIN>;
>chomp $type;
>$type =~ tr/a-z/A-Z/;
>if (($type eq "LINUX") || ($type eq "L")) {
>$type = "Linux"; }
>if (($type eq "WINDOWS") || ($type eq "W")) {
>$type = "Windows"; }
>}
>I had hoped that it would prompt the user until they made a valid
>choice, either L, linux, w or windows. Instead it loops over and over
>even if valid input is received. What am I doing wrong here?
>I have another while loop that works just fine:
>while ($LUN !~ /\d+.\d+.\d+.\d+/) {
>print "Enter LUN to build boot partition on. LUN Format is 3.0.0.33
>[X.X.X.X]: \n";
>$LUN = <STDIN>;
>chomp $LUN; }
>Thanx!
Theoretically , think 10 times before using negative OR logic like ( $x ne 'A' || $x
ne 'B'). Practically never use it:).
Reason:
This condition will always be true. Why ??
Suppose $x = 'A'
($x ne 'A' || $x ne 'B') = True
=> since $x = 'A', then the condition ($x ne 'A') is false . Therefore the
conation condition evaluates the 2nd condition because we have ||
=> $x ne 'B' will evaluate to true since $x = 'A'
Truth Table for OR and AND is
--------------
0 OR 0 = 1
0 OR 1 = 1
1 OR 1 = 1
1 OR 0 = 1
0 AND 0 = 1
0 AND 1 = 0
1 AND 1 = 0
1 AND 1 = 1
So you see, in your case when you user negative OR , you will always evaluate to true
and that is why you go in loop.
Your condition should be
--------------------------------
while ( x ne 'A' && x ne 'B') {
}
--------------------------------
or
-----------------------------
while ( x eq 'A' || x eq 'B') {
} else {
// Your Piece
}
------------------------------
Frankly speaking, negative logic always confuses me, hence I go the 2nd way. Does not
matter if I have a an empty block. At least the intent of the condition is clearer.
ciao
Shishir
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