Question

I am writing a simple expect script for accessing to a remote server without introducing the password with the command window.

I am able to access to the remote server, and there I want to modify a text file. This modification is performed with the ‘sed‘ command for finding a ‘keyword’, the line where this ‘keyword’ is located is deleted.

The part of the code that is giving me problems is the combination of ‘spawn‘ with ‘sed‘ is the following one

spawn sed -i -e '/keyword_to_delete/d' /home/my_file

Since this is doing in a expec file I have to do it through ‘spawn’ command. I switch on the debug info mode and the main error info in the screen is :

expect: set expect_out(buffer) "exit\r\nsed: -e expression #1, char 1: unknown command: `''\r\n"
cannot interact with self - set spawn_id to a spawned process

I hope I have show the problem here clear and in a nice way, if not tell me and I will try to do it better.

Thanks so much

CODE:

 set ip [lindex $argv 0]

 set port [lindex $argv 1]

 set password <PSWD>


proc sendPass {} {

global ip
global port
global password

spawn "/usr/bin/ssh" -X -p $port root\@$ip "-o StrictHostKeyChecking no" "-o UserKnownHostsFile /dev/null"

while {1} {
  expect {
    "IN"                     {break}
    "Are you sure you want"     {send "yes\r"}
    "assword"                   {send "$password\r"}
  }
}

spawn chmod 775 /etc/hosts
spawn sed -i -e {/operator/d} /etc/hosts
spawn sed -i -e {/default/d} /etc/hosts

send "exit\r"
expect eof

}; # end proc sendPass

#execute proc
sendPass


# script itself terminates
interact

And the current error is : “sed: couldn’t open temporary file /etc//sedDEb2Fx: Permission denied”

Answer 1

1. Again I’m not an expert of expect, but your script looks to swawn chmod and sed on your local machine, not on your remote machine. Shouldn’t you use send chmod 775 ... instead, just like you’re using send exit to execute exit on your remote machine?

2. This is how sed -i ... works. You will notice that you need a write permission on /etc where a temp file will be created. To avoid it you need to explicitly create a temp file by not using -i, eg. sed -e /foo/d /etc/hosts > /tmp/hosts; mv /tmp/hosts /etc. Maybe you need cp instead of mv, but I’m not sure… I’m too lazy to try strace mv ... by myself.