calculating variables with decimals

[lawrenzo]

Hi,

in ksh scripting can someone tell me how to calculate decimal numbers ie:

sz=0.5

msz=$(($sz*1024))

echo $msz

0

I know printf will help me out but not sure of the syntax

Thanks

Chris

[Hein van den Heuvel]

SOL

Shells typically deal with integer only.

You can  store the decimal values a piece of string, but the math will be integer.

You will have to reach out to a tool like 'bc' to do the floating point math.

I suspect that the script you are working with is more about parsing and juggling numbers and string

than it is about issuing commands

If so, then personally I would just step into AWK or PERL and do all of those chunks of script there.

Good luck!

Hein

[James R. Ferguson]

Hi:

In addition to using 'bc', 'awk' or Perl as Hein has advised, you could leverage the 'dtksh' shell in lieu of the 'ksh' one.  The 'dtksh' shell is a Korn93 variant whereas the 'ksh' one of HP-UX is Korn88.

You can find 'dtksh' as '/usr/dt/bin/dtksh' (which requires installlation of the CDE bundle on 11.31).

# cat ./mycalc
#!/usrb/dt/bin/dtksh
typeset -E MSZ
typeset -E SZ=.5
MSZ=$((SZ*1024))
echo ${MSG}
exit 0

# ./mycalc

512

Regards!

...JRF...

[Laurent Menase]

in ksh you can also do fix point calculation , if you don"t deal with too small or too large numbers

For instance

If you want to calculate all with 2 decimal digits.

# sz=50
# msz=$(($sz*1024))
# printf "%d.%02d\n" $((msz/100)) $((msz%100))   
512.00

(10.24 + 11.35)*2.35

you do

typeset  -i res

res=$(((1024*1035)*235))

# printf "%d.%04d\n" $((res/10000)) $((res%10000))

24906.2400

 

[lawrenzo · Accepted solution]

ok great thanks for the info everyone.

Chris

[Dennis Handly]

>in ksh you can also do fix point calculation

Yes, exactly what COBOL does automatically.

[Laurent Menase]

>>in ksh you can also do fix point calculation

>Yes, exactly what COBOL does automatically.

Or old assembly uses when floating point coproc was not so common.

In most case it is enough in scripts, keeping an implicit exponent, it is just basic arithmetic

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