Operating System - HP-UX의 주제 Re: Shell Programming

Shell Programming

Scott E Smith — Thu, 19 Jun 2003 16:43:20 GMT

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....

Re: Shell Programming

David Child_1 — Thu, 19 Jun 2003 16:48:53 GMT

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

Re: Shell Programming

James R. Ferguson — Thu, 19 Jun 2003 16:52:07 GMT

Hi Scott:

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

Regards!

...JRF...

Re: Shell Programming

Stuart Abramson_2 — Thu, 19 Jun 2003 16:52:34 GMT

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...

Re: Shell Programming

Dario_1 — Thu, 19 Jun 2003 17:00:59 GMT

Hi!

Try the following:

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

Regards,

Dario

Re: Shell Programming

Hai Nguyen_1 — Thu, 19 Jun 2003 17:01:28 GMT

You can also do this:

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

Re: Shell Programming

Michael Kelly_5 — Thu, 19 Jun 2003 17:11:35 GMT

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.

Re: Shell Programming

James R. Ferguson — Thu, 19 Jun 2003 17:18:10 GMT

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...

Re: Shell Programming

John Meissner — Thu, 19 Jun 2003 17:25:11 GMT

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

Re: Shell Programming

John Meissner — Thu, 19 Jun 2003 17:29:45 GMT

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

Re: Shell Programming

Ian Dennison_1 — Thu, 19 Jun 2003 17:38:25 GMT

Why not just got for a burger? :)

Null points pse. Ian

Re: Shell Programming

Scott E Smith — Thu, 19 Jun 2003 17:44:02 GMT

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

Re: Shell Programming

James R. Ferguson — Thu, 19 Jun 2003 17:45:42 GMT

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...

Re: Shell Programming

Dario_1 — Thu, 19 Jun 2003 17:58:08 GMT

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

Re: Shell Programming

John Meissner — Wed, 25 Jun 2003 11:27:40 GMT

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 &&

Re: Shell Programming

Donny Jekels — Wed, 25 Jun 2003 11:39:19 GMT

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" ]]

Re: Shell Programming

Bill Douglass — Wed, 25 Jun 2003 12:00:40 GMT

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

Re: Shell Programming

Jean-Louis Phelix — Wed, 25 Jun 2003 12:08:17 GMT

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

Re: Shell Programming

Chris Vail — Wed, 25 Jun 2003 13:19:53 GMT

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)