I use `set -e` but it has its own quirks. A couple:

An arithmetic expression that evaluates to zero will cause the script to exit. e.g this will exit:

  set -e
  i=0
  (( i++ )) # exits

Calling a function from a conditional prevents `set -e` from exiting. The following prints "hello\nworld\n":

  set -e
  main() {
     false  # does not return nor exit
     echo hello
  }
  if main; then echo world; fi

Practically speaking this means you need to explicitly check the return value of every command you run that you care about and guard against `set -e` in places you don't want the script to exit. So the value of `set -e` is limited.

More at https://mywiki.wooledge.org/BashFAQ/105

grep has a bad interaction with set -e, since it (infuriatingly) exits with 1 if no lines are matched.

Well, otherwise `if grep "line" $file; then` wouldn't work, which in my opinion is the primary use case for grep in scripts.

I'd still prefer a `grep <args> || true` over not having `set -e` for the whole file.

You can `set +e` before and `set -e` after every such command. I indent those commands to make it look like a block and to make sure setting errexit again isn’t forgotten.

But you probably still want an error if the input file does not exist. To handle grep correctly in a robust manner requires many lines of boilerplate, set +e, storing $?, set -e, distinguishing exit values 0, 1, and 2.