What is the real difference between while and until ?
I'd like to know if it's possible to do an increasingly loop with "until" and a descending loop with while.
Because I saw that if I do this
COUNTER=0
while [ $COUNTER -lt 10 ]; do
echo The counter is $COUNTER
let COUNTER+=1
done
and this
COUNTER=20
until [ $COUNTER -lt 10 ]; do
echo COUNTER $COUNTER
let COUNTER-=1
done
they work well.
But if I do the opposite, for example:
COUNTER=20
while [ $COUNTER -lt 10 ]; do
echo COUNTER $COUNTER
let COUNTER-=1
done
the script doesn't end.
Does this means that we cannot do a reverse loop with a while in bash?
while
runs the loop while the condition is true. until
runs the loop until the condition is true (i.e. while the condition is false).
See http://www.gnu.org/software/bash/manual/bashref.html#Looping-Constructs.