How to redirect output to a log from expect command

Question

I have the following code. How can I redirect the output of the expect to a log file to see if the scp has copied everything successfully. This piece of my code runs in background.

    export L_SRC_SID L_SID MOUNT_POINT SERVICE_PASS APP_SERVER_1 SRC_MOUNT_POINT

    #And now transfer the file over
    /usr/bin/expect -c '
    set timeout -1
    cd /$env(MOUNT_POINT)/$env(L_SID)/apps
    spawn scp -pr apps$env(L_SRC_SID)@$env(APP_SERVER_1):/$env(SRC_MOUNT_POINT)/$env(L_SRC_SID)/apps/* .
    expect {
            yes/no { send yes\r ; exp_continue }
            password: { send $env(SERVICE_PASS)\r }
    }
    expect eof
    '

Answer 1

Simply redirect the output of your invocation of expect:

/usr/bin/expect -c '
set timeout -1
cd /$env(MOUNT_POINT)/$env(L_SID)/apps
spawn scp -pr apps$env(L_SRC_SID)@$env(APP_SERVER_1):/$env(SRC_MOUNT_POINT)/$env(L_SRC_SID)/apps/* .
expect {
        yes/no { send yes\r ; exp_continue }
        password: { send $env(SERVICE_PASS)\r }
}
expect eof
' >> /path/to/logfile 2>> /path/to/errorfile

Or, if you only want to capture the output of scp, redirect only its output:

/usr/bin/expect -c '
set timeout -1
cd /$env(MOUNT_POINT)/$env(L_SID)/apps
spawn scp -pr apps$env(L_SRC_SID)@$env(APP_SERVER_1):/$env(SRC_MOUNT_POINT)/$env(L_SRC_SID)/apps/* . >> /path/to/logfile 2>> /path/to/errorfile
expect {
        yes/no { send yes\r ; exp_continue }
        password: { send $env(SERVICE_PASS)\r }
}
expect eof
'

Answer 2

expect has an oddly named log_file procedure that (drumroll...) logs to files so you can usually just say

#!/usr/bin/env expect
set timeout -1
log_file blah.log
...

within the TCL code. See log_file (and also log_user) in the expect(1) man page for details.