Changes: v4 since v3: * Use $(()) instead of expr(1) for math. v3 since v2: * Use read function instead of cat(1) to read counter value. * Add a newline after the count value in state file and notmuch_counter_value() output. v2 since v1: * Rename $notmuch_counter variable to $notmuch_counter_command. * Rename notmuch_counter() function to notmuch_counter_value(). * Fix documentation for notmuch_counter_value(). * Removed unneeded and add missing "|| return" in notmuch_counter_reset(). * Coding style fixes.