Shulou(Shulou.com)06/02 Report--

Sometimes we need to send ssh commands to the server in batches, but there may be some servers that are newly joined and have not yet been configured with ssh secret-free. At this time, we will be prompted to enter yes/no or password and so on. The expect script command is used to automatically type the corresponding text for us when prompted for this.

Expect script

First, look at a shell script to realize the automatic connection of ssh.

#! / usr/bin/expect spawn ssh 192.168.1.241expect "password" send "123456\ r" expect "] #" {send "ls-la\ r"} interact

Note that the first line uses #! / usr/bin/expect instead of the normal bash script

Spawn is used to start a new process.

Expect "password". Note that this is an internal command in the expect script, which is used to wait for process feedback. It can accept strings and regular expressions. This means that the output of the process started by spawn is regarded as the input of the expect command. If the password script is included, it will output 123456\ r to the standard output.

Note that\ r represents a line break, which is the same as the line break after we enter a command.

Send: send interaction values instead of entering them manually

Then we enter the server of 241and the window will output [root@hadoop01 ~] #, which matches our] #, so we output the ls-la command to the console and wrap. Here we have curly braces after our expect, which is consistent with the effect written on two lines above. It can be understood as another way of writing.

The role of interact is very special, which means waiting for the end of the spawn command and staying at the server to continue interaction. without this, it is possible that the send corresponding to the expect is over before the send is executed. We can use expect eof instead of interact to exit after waiting for the end of spawn (eof will be sent to expect after the end of spawn process)

Multi-branch syntax

The above expect belongs to the single branch pattern, which represents a match. If the match is not, you have to type it yourself, but we may have a different prompt the first time, and you need to use multi-branch syntax at this time.

Expect will be output as long as it matches to either aaa or password.

#! / usr/bin/expectspawn ssh 192.168.1.241expect {"aaa" {send "bbb\ r"} "password" {send "nf123456\ r"}} expect "] #" {send "ls-la\ r"} interact

Expect command line arguments

The above expect script functions may have been achieved, to avoid having a lot of expect scripts, I prefer to use the expect command

#! / bin/bashSERVER= "192.168.1.241" PASSWD=nf123456expect-c "set timeout-1; spawn ssh $SERVER; expect {\" yes/no\ "{send\" yes\ r\ "; exp_contine;}\" password:\ "{send\" $PASSWD\ r\ "; expect\"] #\ "{send\" ls-la\ r\ "} Expect\ "] #\" {send\ "exit\ r\"}; expect eof; "

The above shell function is the same as that of the expect script, which is entered after logging in through ssh, the ls-la command

Set timeout-1 sets the timeout

Expect needs to be followed by-c

The expect command is enclosed in double quotation marks, which should be noted

If there is a "need to use\" escape.

Line 15 represents the end of the ls-la command to send an exit command, which generally needs to be added to prevent blocking

End of expect eof matching spawn

Ssh batch secret-free demo

#! / bin/bashSERVERS= "192.168.1.241 192.168.1.242" PASSWD= "123456" function sshcopyid {expect-c "set timeout-1; spawn ssh-copy-id $1; expect {\" yes/no\ "{send\" yes\ r\ "; exp_contine;}\" password:\ "{send\" $PASSWD\ r\ "; exp_continue;}} Expect eof; "} for server in $SERVERSdo sshcopyid $serverdone

The above is the whole process of the expect command to achieve batch ssh secret-free under linux. I hope it can help you.

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