Linux Return Code

Linux Command Success or not

root@mariadbcluster-0:/# ls
bin   data  dev  home  lib64           media  opt   root  run.sh  srv  tmp  var
boot  db    etc  lib   mariadbcluster  mnt    proc  run   sbin    sys  usr

A failed test

root@mariadbcluster-0:/# ls |grep aa
root@mariadbcluster-0:/# res=$?
root@mariadbcluster-0:/# echo $res
1

A Success test

root@mariadbcluster-0:/# ls |grep mnt
mnt
root@mariadbcluster-0:/# res=$?
root@mariadbcluster-0:/# echo $res
0

The res =0 is success and =1 is failed. where $? is get the previous result.