Array with only even number - bash

Question

for X in {18..2500} ; is one line of my script, which means to pick number one by one like: 18,19,20,21,22,23....till 2500
However I find I only need even number right now: 18,20,22,24.....2500
Then what should I do by a slight modify of the line?
Thanks
edit:
It's bash...
My script is now changed to:
#!/bin/bash
TASK=1101;
NUM=9;
TEND=1100;
for X in {18..2500};{
if (X % 2 == 0);
do
echo "$X echo \"Wait until $NUM job is done\" $NUM" ;
NUM=$((NUM+2)) ;
X=$((X+1)) ;
TEND=$((TEND+100)) ;
echo "$X -t $TASK-$TEND jobs.sh" ;
TASK=$((TASK+100)) ;}
done
but got errors like:
line 15: syntax error near unexpected token `do'

Answer 1

You can specify the increment:
for X in {18..2500..2}
A sequence expression takes the form {x..y[..incr]}, where x and y are
either integers or single characters, and incr, an optional increment, is
an integer.
Or
for X in `seq 18 2 2500`

Answer 2

This is not C++. This is a bash script.
Your for-loop needs to start with a do:
for X in {18..2500}; do
Your if-statement syntax looks off. It should probably be something like this, note the then:
if [[ $((X % 2)) == 0 ]]; then
if-blocks end with:
fi
And the for-do block ends with:
done
Better still... do away with the if statement and use Bash's for-loop construct to generate only even numbers:
for ((X = 18; X <= 2500; X += 2)); do
echo "$X echo \"Wait until $NUM job is done\" $NUM" ;
# ...
done

Answer 3

Try the modulus operator. In almost all languages, it'll look something like this:
if (x % 2 == 0) // …Do something
That is valid C code, but can easily be applied to other languages.
You can think of the mod operator as a division sign placed in the same location, but rather than returning the results of the division it returns the remainder. Therefore in this code, if the remainder of a divide-by-two is 0, then it divides evenly by two, and so it's even by definition.

Answer 4

If your language has a for(;;) syntax you can
for (X = 18; X <= 2500; X += 2)

Answer 5

There are a couple things you can do:
use the modulus function for your language:
for x in {18..2500} {
if (x mod 2=0) {
do something;}
step through your For loop 2 at a time:
for x in {18..2500} step 2 {
do something;}