To increase similarity with regular shells, the handler signature could be changed to
int handler(int argc, char **argv);.

The return value 0 would indicate success, anything else would be treated as an error.

The shell would need to be changed to iterate over the whole string with strtok, counting the parameters and to check the return value of the handler. If an error occurred the shell could print a message.

All shell commands would need to be updated for the new signature.

Pros:

• shell commands can communicate errors more easily (just return 1)
• no need for use of the unfamiliar strtok within the commands
• easier portability of existing commands

Cons:

• commands loose the ability to sscanf through parameters expecting spaces