Avoid bash script waiting for user enter the Enter key

Question

I have the following entry in a bash script:

 echo "Please see attached file" | mailx -S smtp=$smtpServer -s "Subject of the mail" -a $logfile -r "sender@domain.com" receiver1@domain.com receiver2@domain.com

It's working fine if there is no error in sending mail, but if there is an error, mailx will show the error message and wait for user to press the enter key. How can I want to avoid that? It should not wait for the user to press the enter key.

Answer 1

You would normally try to use the application switches for non-interactive mode or suppressing errors for this. I didn't find any explicit ones for mailx after quick skim of the docs, however.

A more general approach of doing this would be to use the timeout command for this, which runs the specified command and kills it if it is still running after specified timeout.

For example, in your case, the command would be:

echo "Mail body" | timeout 15s mailx ${MAILX_OPTIONS}

This command will kill mailx if it's still running after 15 seconds, which should be only in the case of a lingering error message.

Answer 2

In the gross-hack category of solutions, send along a gratuitous carriage return, which will be there if needed, and thrown away if not:

{ echo "Please see attached file"; echo; } | mailx ...

Answer 3

You can run the command in an expect shell, which will watch allow you to look for prompts and send information in response.

#!/usr/bin/expect
spawn COMMAND
expect "PROMPT"
send "RESPONSE\n";
interact