Conditional ef/elif in scripting

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# 1  
Old 08-07-2011
Conditional ef/elif in scripting

Hi everyone,

I'm slowly teaching myself shell scripting. I only have one reference book at the momement and i am stuck on a conditional if /elif problem

I have a basic Fahrenheit to Celsius converter script with a condition based on temperature echo output.

There are five conditions, but whenever i run the script it outputs the first and ignores the rest regardless.

#Usage: To convert Fahrenheit to Celsius
echo "Fahrenheit to Celsius Converter 0.1"
echo         "by Me"
echo "Enter Temperature in Degrees Fahrenheit"
read F
#forumla C=(5/9)*(F-32)
C=$(echo "scale=2;(5/9)*($F-32)" |bc)
echo "$F degress Fahrenheit is = $C degrees Celsius"

if [ "$C -lt 0" ] || [ "$C -ge 50" ]
        echo "Too hot or cold to even think about!"
elif [ "$C -ge 30" ] && [ "$C -lt 50" ]
        echo "Such a HOT DAY!"
elif [ "$C -ge 20" ] && [ "$C -le 30" ]
        echo "That sounds like a pleseant day!"
elif [ "$C -ge 10" ] && [ "$C -le 20" ]
        echo "Ooo, thats a cool day. Better dress warmly"
elif [ "$C -ge 0" ] && [ "C$ -le 10" ]
        echo "SO COLD! I'm staying in today!"


What am I doing wrong here?
# 2  
Old 08-07-2011
You've got your quotes wrong in your conditional expressions.

if [ "$C -lt 0" ] || [ "$C -gt 50" ]

should be
if [ "$C" -lt 0 ] || [ "$C" -gt 50 ]

The non-empty string of the first expression will always be true.
# 3  
Old 08-07-2011
Thanks agama Smilie

But now i get an err "integer expression expected" on each elif line (twice on the first)
# 4  
Old 08-07-2011
Then check (with echo "$C") what really you have. Or better add 'set -x' to the beginning of your script (as the second line) and see what happens.
This User Gave Thanks to yazu For This Post:
# 5  
Old 08-07-2011
The output of the top half of the script when provided a number of say 100 (degrees) is calculated to 37.40.

The exact err output i get (in the first instance) is

./ line 12: [: 37.40: integer expression expected

# 6  
Old 08-07-2011
Ok. /bin/sh can't work with floating numbers. Truncate them (sed 's/\..*//') or not use scale in bc evaluation, or use bc in test conditions or use awk or ... (a lot).
# 7  
Old 08-07-2011
haha. Thanks yazu.... much to learn, i still have.....
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