topic Re: Can not seem to get this IF statement to work in Operating System - HP-UX

Can not seem to get this IF statement to work

Scott Frye_1 — Tue, 21 Dec 2004 13:05:20 GMT

I have three variables
$WCPU = 0.48
$HIGHWATER 0.10
$COUNTER 1
I want to do something like this
If $WCPU is greater than or equal to $HIGHWATER AND $COUNTER is equal to 0 then do something.

I've tried if [$WCPU -ge $HIGHWATER -a $COUNTER -eq 0] but it doesn't work. I get
./toptest.sh[23]: [0.48: not found.

Re: Can not seem to get this IF statement to work

Scot Bean — Tue, 21 Dec 2004 13:14:16 GMT

When using -ge, you need double brackets, also whitespace.

Try [[ $WCPU -ge $HIGHWATER -a $COUNTER -eq 0 ]]

Re: Can not seem to get this IF statement to work

Jerry Jordak — Tue, 21 Dec 2004 13:14:19 GMT

Leave a space between the brackets and the characters inside, like this:

if [ $WCPU -ge $HIGHWATER -a $COUNTER -eq 0 ]

From your error message, it appears the shell is trying to evaluate [$WCPU as a command.

Also, AFAIK, ksh can only handle integers in variables for purposes of determining greater than and less than. It will evaluate 0.48 and 0.10 as 0 in the if statement. You may want to change your numbering to use integers instead.

-JWJ

Re: Can not seem to get this IF statement to work

Scott Frye_1 — Tue, 21 Dec 2004 13:22:03 GMT

Jerry,

What are you suggesting I do with my variables?

Re: Can not seem to get this IF statement to work

Pete Randall — Tue, 21 Dec 2004 13:25:08 GMT

Scott,

Isn't this similar to the problem you had a while back:

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=737698

To quote Clay, "The problem is that the shell only does integer arithmetic. Use awk or bc."

Pete

Re: Can not seem to get this IF statement to work

Jerry Jordak — Tue, 21 Dec 2004 13:28:32 GMT

In cases like this, where I know I might have numbers with values between 0 and 1, I've multiplied the values of the variables by 100, so that the if statements will work properly.

For example, if you define the variables as so:

WCPU=48
HIGHWATER=10

then it will work. If you're getting the $WCPU value from another command or a script, you may need to convert it, by removing the decimal point.

Re: Can not seem to get this IF statement to work

Scott Frye_1 — Tue, 21 Dec 2004 13:32:15 GMT

Pete,

I believe that is in the same ball park. I had forgetten about that thread. I quickly manned bc and I found it does not currently support && or ||. Also, I'm not clear on it usage in my if statement.

If you have done anything like this before, I would enjoy seeing some examples.

Thanks again for refreshing my memory.

Scott

Re: Can not seem to get this IF statement to work

Pete Randall — Tue, 21 Dec 2004 13:38:07 GMT

Scott,

I'm not all that great on shell scripting myself - I only stumbled over that thread while I was searching the ITRC for a solution to your problem.

Pete

Re: Can not seem to get this IF statement to work

Michael Schulte zur Sur — Tue, 21 Dec 2004 14:31:15 GMT

Scott,

if you format wcpu and highwater the same way you can compare them as strings.
WCPU=`printf %06.2f 0.48`
HIGHWATER==`printf %06.2f 0.10`
if [ "$WCPU" > "$HIGHWATER" ]..

greetings,

Michael

Re: Can not seem to get this IF statement to work

Chris Vail — Tue, 21 Dec 2004 17:52:10 GMT

As others have pointed out, ksh only does integer math. You can fix your numbers with:
NCPU=(( "$WCPU" * "100" ))
NHIGHWATER=(( "$HIGHWATER" * "100" ))
if test "$NHIGHWATER" -eq "$NCPU" -a "$COUNTER1" -eq "0"
then
do something
fi

The double parenthesis is ksh's version of the "let" statement.

Re: Can not seem to get this IF statement to work

A. Clay Stephenson — Tue, 21 Dec 2004 18:13:52 GMT

NCPU=(( "$WCPU" * "100" ))
is going to evaluate as 0 if ${WCPU} is 0.48)

Here's a method to leverage bc for the floating-point evaluation. It will return 1 if ${WCPU} >= ${HIGHWATER} and 0 otherwise.

#!/usr/bin/sh

WCPU=0.48
HIGHWATER=0.10
COUNTER=1

typeset -i A=$(echo "a = 0; if (${WCPU} >= ${HIGHWATER}) a = 1;a" | bc)
# now we can do a compound if
if [[ ${A} -ne 0 && ${COUNTER} -eq 0 ]]
then
echo "Do your thing"
fi

Re: Can not seem to get this IF statement to work

Michael Schulte zur Sur — Wed, 22 Dec 2004 07:27:49 GMT

Clay,

your routine does not work if for example
WCPU=10.10
HIGHWATER=4.1

It seems that not every shell supports string1 > string2 comparisons.

Inspired of Chris another try:
#!/usr/bin/sh -x
WCPU=`eval echo 0.08 | awk '{printf("%06.2f",$1*100)}'`
HIGHWATER=`eval echo 0.18 | awk '{printf("%06.2f",$1*100)}'`
if test ${WCPU} -gt ${HIGHWATER}
then
echo do your thing
fi

greetings,

Michael

Re: Can not seem to get this IF statement to work

Scott Frye_1 — Wed, 22 Dec 2004 08:25:01 GMT

Thank you to all who posted to this thread. Although I'm not quite clear what it is doing yet (I love learning this way), I'm going to take Clay's approach.

Thanks again to all.