Expect的生成将ssh的-i解释为自己的

Question

In expect, is there some way to quote the command run by spawn? An expect script which pushes the public key from one AWS instance to another AWS instance, spawn manipulates the command such that ssh's -i option becomes a invalid cat option.

The script.

#!/usr/bin/expect -d 

spawn sudo -s cat /root/.ssh/id_rsa.pub | ssh -i /tmp/key.pem ec2-user@ip-50-101-23-6 sudo -s 'dd of=/root/.ssh/authorized_keys oflag=append conv=notrunc'
expect {
    "*yes/no*"    { send "yes\r"; exp_continue }
}

The error.

$ pushSSH.expect
expect version 5.44.1.15
argv[0] = /usr/bin/expect  argv[1] = -d  argv[2] = ./pushSSH.expect                        
set argc 0
set argv0 "./pushSSH.expect"
set argv ""
executing commands from command file ./pushSSH.expect
spawn sudo -s cat /root/.ssh/id_rsa.pub | ssh -i /tmp/key.pem ec2-user@ip-50-101-23-6 sudo -s 'dd of=/root/.ssh/authorized_keys oflag=append conv=notrunc'
parent: waiting for sync byte
parent: telling child to go ahead
parent: now unsynchronized from child
spawn: returns {13106}

expect: does "" (spawn_id exp4) match glob pattern "*yes/no*"? no
cat: invalid option -- 'i'
Try `cat --help' for more information.

expect: does "cat: invalid option -- 'i'\r\nTry `cat --help' for more information.\r\n" (spawn_id exp4) match glob pattern "*yes/no*"? no
expect: read eof
expect: set expect_out(spawn_id) "exp4"
expect: set expect_out(buffer) "cat: invalid option -- 'i'\r\nTry `cat --help' for more information.\r\n"

Does the command work when run manually? Yes.

sudo -s cat /root/.ssh/id_rsa.pub | ssh -i /tmp/key.pem ec2-user@ip-50-101-23-6 sudo -s 'dd of=/root/.ssh/authorized_keys oflag=append conv=notrunc'
0+1 records in
0+1 records out
401 bytes (401 B) copied, 7.8214e-05 s, 5.1 MB/s

OS: Red Hat Enterprise Linux Server release 6.7 (Santiago)

expect version 5.44.1.15

Answer 1

Expect's spawn command executes its arguments directly without passing them to a shell. This means that shell constructs like i/o redirection and pipelines won't work. When you run...

spawn sudo -s cat /root/.ssh/id_rsa.pub | ssh -i /tmp/key.pem ...

...expect is passing /root/.ssh/id_rsa.pub and everything after that as arguments to the cat command.

If you want to run a shell pipeline, you need to explicitly start a shell and pass it the command line:

spawn sh -c {sudo -s cat /root/.ssh/id_rsa.pub | ssh -i /tmp/key.pem ...}

For example:

expect1.7> spawn sh -c {echo hello world | sed s/world/nurse/}
spawn sh -c echo hello world | sed s/world/nurse/
14450
expect1.8> expect EOF
hello nurse
expect1.9>