test for odd number

B-Boy · 08-12-2008, 06:09 AM

Hi guys I need help again...how can i check if a var is an odd number

matthewg42 · 08-12-2008, 06:24 AM

In any particular language, or a general method? In general you do a mod 2 and see if the result is 0 or 1.

B-Boy · 08-12-2008, 06:30 AM

Quote:

Originally Posted by matthewg42

In any particular language, or a general method? In general you do a mod 2 and see if the result is 0 or 1.

in bash scripting

ta0kira · 08-12-2008, 06:48 AM

Try this:

Code:

if [ $(echo "$value%2" | bc) -eq 1 ]; then
  echo "$value is an odd number"
fi

ta0kira

B-Boy · 08-12-2008, 07:35 AM

Quote:

Originally Posted by ta0kira

Try this:

Code:

if [ $(echo "$value%2" | bc) -eq 1 ]; then
  echo "$value is an odd number"
fi

ta0kira

thanks that is exactly what i needed

Hko · 08-12-2008, 07:35 AM

Running bc only to see if a number is od or even looks a bit like an overkill to me.

Faster version:

Code:

if [ $(($value%2)) == 0 ]; then
    echo Even
else
    echo odd
fi

sundialsvcs · 08-12-2008, 09:54 PM

The "traditional" way I've seen it done is by a logic-AND with $01. This tests the least-significant bit: zero means even.

Code:

if (foo & 0x01) {
  // number is odd
} else {
  // number is even
}

B-Boy · 08-13-2008, 12:22 AM

thanks guys