Script for testing SFTP login status?

I've written expect and bash scripts to work this.... (though it can get fancier as mentioned above).

Bash script: executed with three arguments: user, pass, and host. For example ./bwrap.sh ninja_user ninja_star1234 ninja.com

The script creates a log file which later used for checking successful log in/out.

#!/bin/bash

# log file
log="connection_test.log"
if [ -f $log ];
then
    echo "Older file $log exists, removing and creating new..."
    rm -rf $log
    touch $log
else
    echo "Creating log file"
    touch $log
fi

# running expect script.
# arg 1 is user, arg 2 is pass, arg 3 is host 
./one.exp $1 $2 $3  >> $log

# checking log for connections 
if grep --quiet logout $log; then
    echo "connection successful, proceeding to backup" >> $log
else
    echo "connection failed, please check server" >> $log
    exit 1
fi

Now to the expect script, it has a timeout of 10 seconds, and I actually prefer to work w/o strict host key. If you do want to work with strict host key edit the relevant line and add an expect "yes/no" ....

#!/usr/bin/expect -f

set user [lindex $argv 0];
set password [lindex $argv 1];
set host [lindex $argv 2];

set timeout 10
# now ssh
spawn ssh $user@$host -o StrictHostKeyChecking=no
match_max 100000 # Look for passwod prompt
expect "*?assword:*"
# Send password aka $password
send -- "$password\r"

expect "*$ "
send -- "whoami\r"
expect "<user name>"  # change user
send -- "exit\r"
expect eof

Hope this helps.

For sftp connection please: add line to bash script where $4 is port

./one.exp $1 $2 $3 $4 >> $log

add line to expect script:

set port [lindex $argv 3];

replace in expect script

spawn ssh $user@$host -o StrictHostKeyChecking=no

with

spawn sftp $host@$user -o Port=$port StrictHostKeyChecking=no

and

 expect "*$ "

with

expect "sftp>"

Since I do not have an SFTP server to test it on, the changes are made based on [this question]: sftp a file using shell script

Also, [expect homepage]: http://expect.sourceforge.net/ might be handy.

Lastly, reading your comment regarding a straight forward approach, it's possible to simply use nc and see if the host:port is up. For this you can use:

#!/bin/bash

# log file
log="connection_test.log"
if [ -f $log ];
then
    echo "Older file $log exists, removing and creating new..."
    rm -rf $log
    touch $log
else
    echo "Creating log file"
    touch $log
fi

# nc
nc_command=`nc -z -w 5 $1 $2 | tee -a $log`
if [[ $nc_command == *succeeded* ]];
then
    echo "Server is listening, ready for backup" | tee -a $log
else
    echo " Server seems to be offline, please check" | tee -a $log
    exit 1
fi 

To run the last script use: ./test.sh host port

If by chance, your backup script is based on Python, you might want to check out check_sftp, a so-called active check brought with Checkmk. It has the specific use-case of checking SFTP servers. Since it is based on Python and the pure-Python SSH implementation Paramiko, all you need is Python. It contains a few Checkmk specifics such as the password store and OMD_ROOT integration, which you might need to rip out to get it to work standalone. But it is somewhat sophisticated, including options to PUT or GET files or even compare timestamps on the server, so it might be worth a try. Since it adheres to the Nagios Check Plugin Guidelines, you can rely on the exit code 0 for success.

Another Python-based option might be Fabric (which is also based on Paramiko), or using the SFTP module of Paramiko directly.

You could test sftp connectivity by just doing an ssh connection test:

if $(ssh -q [email protected] exit)
then
    echo yes
fi

If the server does not allow ssh, you could do use nmap but that doesn't test key authentication:

nmap myserver.bfworks.com -PN -p ssh | grep 'open'