Shell Programming and Scripting

Hi, i',m new to bash scripting and i have the following scrip,
however, when i try to executig it i get an error saying "traveltime: line 6: * 60: syntax error: operand expected (error token is "* 60")"
however, i can't see why it would say that. I though that would be ok. Can somebody tell me how i can solve this please. thanks

Try this in place of the existing MINUTES= line. It takes the number of minutes in the derived HOURS and subtracts from the original number of minutes.

Code:

MINUTES=$(( $TOTMINUTES - ($HOURS \* 60) ))

./testscript 121 60

The trip will take 2 hours and 1 minutes

Stop press.

Got it working by escaping the percent sign (i.e. the remainder from the calculation) with:

Code:

MINUTES=$(($TOTMINUTES \% 60))

works out of the 'box' for me on FC12.
nice work, btw.

You don't need to put dollar signs inside the evaluation brackets. $((A+B)) is perfectly valid if A and B are variables containing integers.

You'd get this error if you didn't pass any parameters in on the command line. If no parameters are passed to the script, the $1 (line 6) would evaluate to null and the resulting expression would be

Code:

$(( * 60 ))

which is missing an operand. You could avoid this by testing for the number of parameters passed to the script and aborting if one is missing:

Code:

if $(( $# < 2 )) 
then
   echo "missing parameter(s); expected: distance speed"
fi

If you are not familiar with it, the variable $# evaluates to the number of parameters passed to the script (or to a function if the code is inside of a function).

Mythl, thanks for your reply, i adjusted my code to

Code:

 

#X60=$(($1 * 60))
TOTMINUTES=$(($X60 / $2))
HOURS=$(($TOTMINUTES / 60))
MINUTES=$(($TOTMINUTES \% 60))

i get this error ": line 12: / : syntax error: operand expected (error token is "/ ")" what should it look like in full?
Also, i'm using sh traveltime to execute my script, is that still a valid way or doing it as i'm still new to this?

Hi.

Code:

#X60=$(($1 * 60))

Is this a comment, a typo or a command prompt?

Code:

TOTMINUTES=$(($X60 / $2))

would certainly fail it it's a comment.

It's often helpful to run your script with

Code:

set -x

This will show you exactly what is failing.

You might also want to add some validation for command-line parameters.

Either, for example:

Code:

if [ $# -ne 2 ]; then
  echo "Usage: ...."
  exit
fi

or

Code:

X60=$(1:-1}