Expect does not detect string - shell

Question

I need to automate the input of a string in a command called from a shell (sh) script, using expect To accomplish this I have:
#!/bin/sh
MY_ARGS="-a -b -c" expect -c "
spawn mycommand $MY_ARGS
expect 'continue, I know what I am doing' { send -- 'continue, I know what I am doing\r' }
expect eof"
The mycommand output is:
Enter "continue, I know what I am doing" to use the outdated data anyway:
But the string is not being detected and therefore nothing is sent. What is wrong with the expect command?
Thanks.

Answer 1

There's a few things going on here:
When you write var=value some_command, then $var is set in the environment for the command.
Inside expect you need $env(MY_ARGS)
But now you have a quoting problem, you can't put the expect body in double quotes because you
don't want the shell to expand that variable.
#sexpect_Expect.for.Shells is right, single quotes are not special in Tcl (and hence expect). expect sees this:
expect {
{'continue,} {I}
{know} {what}
{I} {am}
{doing'} { send -- "'continue," "I" "know" "what" "I" "am" "doing\r'" }
}
To solve the quoting problems, I recommand using a quoted heredoc in the shell
export MY_ARGS='-a -b -c'
# .......v..........v these quotes are crucial
expect <<'END_EXPECT'
set phrase "continue, I know what I am doing"
set timeout -1
spawn mycommand {*}$env(MY_ARGS)
expect $phrase
send -- "$phrase\r"
expect eof
END_EXPECT
Note how I expanded the env variable: {*}$env(MY_ARGS) -- the {*} syntax splits the variable content into separate words.