multiple conditions in if statements

Shell Programming and Scripting
1

Hi all, I'm confused about the proper syntax for multi-conditional if then statements. I'm trying to set limitations on info input on the command line.. i.e.

if [$x=[+|-|/|*|%]] ;then
$x=$vr1
else
print "You have entered an invalid option."

Can someone please clue me in on what is wrong with my syntax; what teh correct syntax is for using "and" "or" in similar statements.

2

Try this !

if [ $i = "+" -o $i = "-" -o $i = "/" -o $i = "%" ]; then
$x=$vr1
else
print "You have entered an invalid option."

3

Just to add:.... and is represented by "-a".

4

On assignments to a variable, do x= instead of $x= .

When you use a mixture of -o and -a, you might have to control precedence. In the following, the first line would test true because -o has precedence:
if [ a = a -o b = b -a c = C ]
But add parentheses (you would need to backslash these) and it would now test false:
if [ ( a = a -o b = b ) -a c = C ]

Also, when checking for several values, a case statement makes for nice clean code, and even more handy when each value will result in a different action:

case $x in
 +|-|/|%) x=$vr1;;
       *) print "You have entered an invalid option."
          exit 1;;
esac