Shell Programming

[Scott E Smith]

Hello all...
I am attempting to ensure that the value of a given variable matches one of three strings.
Basically it's
if "$PIE" does not equal "cherry" "apple" or "pumpkin" then i want to exit the loop and print the usage statement. If it does match then i want the loop to continue.
My syntax is as follows but does not work, I think is may be an -0 or || compund expression issue.... Thanks.
#!/usr/bin/sh
PIE=cherry

if [ "$PIE" != [ "apple" || "cherry" || "pumpkin" ]]
then
echo "\n****Valid names are apple,cherry or pumpkin!\n" ; exit 1
else
echo "\n****Name is valid!\n"

Thanks in advance for the help....

[David Child_1 · Accepted solution]

Try:

case $PIE in
apple) echo "\n****Name is valid!\n" ;;
cherry) echo "\n****Name is valid!\n" ;;
pumpkin) echo "\n****Name is valid!\n" ;;
*) echo "\n****Valid names are apple,cherry or pumpkin!\n" ; exit 1 ;;
esac

[James R. Ferguson]

Hi Scott:

...
# if [ "$PIE" != "apple" -a "$PIE" != "cherry" -a "$PIE" != "pumpkin" ]; then
> echo "bad pie!"
> else
> echo "yummy pie!"
> fi

Regards!

...JRF...

[Stuart Abramson_2]

I don't think that "if" works that way.

I would probably do that with "case":

case $PIE in
pumpkin) print "Thank you.";;
cherry | apple) print "Gracias.";;
*) print "Wrong answer. Sorry..."
exit;;
esac
# Process pie


statements...

[Dario_1]

Hi!

Try the following:

if [ "$PIE" != "apple" -o "$PIE" != "cherry" -o "$PIE" != "pumpkin" ]
then
echo "Not good"
else
echo "Goood!"
fi

Regards,

Dario

[Hai Nguyen_1]

You can also do this:

if [ $PIE = apple -o $PIE = cherry -o $PIE = pumpkin ]
then
echo true
else
echo wrong
fi

[Michael Kelly_5]

Scott,
this is a logic problem.
The logic says
"If $PIE is not equal to "apple" OR if $PIE is not equal to "cherry" OR if $PIE is not equal to "pumpkin"
then
echo "\n****Valid names are apple,cherry or pumpkin!\n" ; exit 1
else ...

As written, $PIE is not equal to "apple" so the test is TRUE and because it is TRUE, the shell will not evaluate the rest of the tests and it executes the first echo command.
The way to do this is by using an AND operator.

Here is a version that will do what you want.

#!/bin/sh
PIE=cherry

if [ "$PIE" != "apple" -a $PIE != "cherry" -a $PIE != "pumpkin" ]
then
echo "\n****Valid names are apple,cherry or pumpkin!\n" ; exit 1
else
echo "\n****Name is valid!\n"
fi

HTH,
Michael.

[James R. Ferguson]

Hi:

Do *not* [no pun intended] use the 'or' operator [ -o ] with negatated equality checks. You will not achieve the desired outcome. Try this:

# PIE=apple

# [ "$PIE" != "apple" -a "$PIE" != "cherry" -a "$PIE" != "pumpkin" ] && echo BAD_PIE!

...now change '-a' to '-o':

[ "$PIE" != "apple" -o "$PIE" != "cherry" -o "$PIE" != "pumpkin" ] && echo BAD_PIE!

Regards!

...JRF...

[John Meissner]

if [ "$PIE" != "apple"] || [ $"PIE" != "cherry" ] || [ "$PIE" != "pumpkin" ] ;
then
echo "Usage: `basename $0` {whatever options}"
exit
else
#whatever commands you wnat
fi

[John Meissner]

looking at everyone's replies... isn't it interesting how many differnt approaches there are as well as the ones we choose to take?

[Ian Dennison_1]

Why not just got for a burger? :)

Null points pse. Ian

[Scott E Smith]

You guys all kick A$$..... Thanks a bunch. Ian you get points for humor...

[James R. Ferguson]

Hi John M:

Your example should be use "&&" not "||" as:

# if [ "$PIE" != "apple" ] && [ "$PIE" != "cherry" ] && [ "$PIE" != "pumpkin" ]
> then
> echo BAD_PIE
> else
> echo GOOD_PIE
> fi

Regards!

...JRF...

[Dario_1]

James:

Thank you for shaking my head. I used your approach (trying to avoid the typing) but using the -o option and forgot to remove the exclamation (!). You are totally correct....Thank you for the correction.

Regards,

Dario

[John Meissner]

James,
No - my example is correct. He's asking if pie does not equal apple OR pumpkin - hence the || operator. Whereas if he was checking to see if pie does not equal applor AND pumpkin then i'd use the &&

[Donny Jekels]

Scott,

use the shell's built in test operator.

the next if statement calls an external test operator;

if [ $PIE = xxx ]; then blabla
fi

for faster processing use the internal test operator

if [[ "$PIE" != "apple" -a "$PIE" != "cherry" -a "$PIE" != "pumpkin" ]]

[Bill Douglass]

Case-insensitive example:

#!/bin/sh
PIE=$1
if echo $PIE | egrep -i -q -e "^apple$|^cherry$|^pumpkin$"
then
echo "$PIE pie; umm-umm-good"
else
echo "I don't know about $PIE pie"
fi

[Jean-Louis Phelix]

Hi,

This variant uses 'select' : you have to choose a number instead of a fruit. See 'select' in man sh-posix.

Regards.

#!/usr/bin/sh
export PS3="Enter Fruit "
select VAR in apple cherry pumpkin
do
[ -z "$VAR" ] &&
{
echo "$REPLY is note a correct choice, exiting ..."
break
}
echo "You've chosen a $VAR"
done

[Chris Vail]

The best solution, as pointed out by others is to use the case statement. But since you also asked for other solutions, here's a wierd one:

echo $PIE|egrep '^(apple|cherry|pumpkin)' 2>&1 > /dev/null
if test "$?" ne "0"
then
echo "ICKYPOO!!! I don't like $PIE pie!"
else
echo "Yummmm: a $PIE pie!"
fi

Chris<--regexps are your friend......
(if sometimes a very confusing friend)