What is: do if [ $i -nt ${LOG_DIR_PATH}/test ]

What does -nt do for this case?

LOG_DIR_PATH=/home/users/chinboon/test-chinboon/logs/sandbox1

do if 开发者_Go百科[ $i -nt ${LOG_DIR_PATH}/test ] 

The -nt flag checks if file $i has a more recent modification date than file ${LOG_DIR_PATH}/test.

See man 1 test for all available flags.

I am pointing you to man test since

if [ $i -nt ${LOG_DIR_PATH}/test ]; then
   # SOMETHING
fi

is a shorthand for

if test $i -nt ${LOG_DIR_PATH}/test; then
   # SOMETHING
fi

According to IBM DeveloperWorks the purpose if -nt is to

Test if file1 is newer than file 2. The modification date is used for this and the next comparison.

So basically you're checking if the file whose filename is stored in $i is newer than the file with filename ${LOG_DIR_PATH}/test.