set -e creates two problems. The first is that what is considered "failure" by the shell is not consistent or intuitive. The second is that what each of your

set -e creates two problems. The first is that what is considered "failure" by the shell is not consistent or intuitive. The second is that what each of your tools consider failure is also not necessarily intuitive. You're getting a false sense of security at best. E.g. grep considers no matches worthy of a non-zero (a.k.a. error) exit code while df considers an invalid block size an error worthy of a exit code of zero. Ostensibly printf(1) exits with non-zero on an error, but a format specifier with insufficient arguments is not an error.