First, format:
while conditions tested; do
Loop
done
Second, the test conditions
Condition testing is to meet the conditions will have been implemented.
such as:
let i =0
while i < 100;do
echo $i
i++
done
Note: here as long as i is less than 100 have been executed will continue, so the body of the loop, i must change, otherwise it will be caught in an endless loop.
Three, while if mixed with
while conditions tested; do
if conditional formula; then
command
be
done
Four, while reading the file
while read file ；do
Loop
done < file_name
Five, until
until and while the opposite, while a condition is satisfied execution cycle, until the condition is not met execution cycle
until the test condition; do
Loop
done
Sixth, the combination of test conditions
Logic and: a plurality of conditions are satisfied
[[Condition 1 && condition 2]]
Or logic: a plurality of conditions are satisfied
[[Condition 1 || condition 2]]