Running Plink in a Windows Batch - Issues

Question

I'm putting together a very basic automation script using the windows batch operation in which will loop through a list of IP addresses and run a plink command to logon and keep alive the account on the server because it has recently logged onto the server.

I believe I have most of the function working however I am having an issue with passing through the password. I'm seeing an issue where if the password I have has special characters and in which I run the script through command prompt it does not pass through the special character to the plink command. Here is a look of the script:

@echo on

SET userid=root
SET passwd=Welcome1%

for /f "delims=" %%i in ('type "ipaddress.txt" ') do (
pushd "C:\Program Files (x86)\PuTTY"
plink.exe -pw %passwd% %userid%@%%i hostname
popd
)

The ipaddress.txt file contains:

10.0.0.1
10.0.0.2
10.0.0.3

The idea is to go through the list for each IP address, logon and validate access. I'm also looking to ensure the value Y or N is passed to make sure a server is trusted or not as part of the script. Any help would be greatly appreciated.

Answer 1

You could see your script behaviour with @echo on (run it from within a cmd window instead of double-clicking). You are right that some special characters need to be escaped. If your password should be Welcome1% literally then use

SET passwd=Welcome1%%

or advanced set command syntax

SET "passwd=Welcome1%%"

Edit. Above advice covers particularly % percentage sign in a string. However, escaping some characters with special meaning (e.g. redirectors <, >, |, & etc.) as ^<, ^>, ^|, ^& seems to be a bit inconvenient and could not suffice. Therefore required advanced set command syntax and delayed expansion enabled instead.

For instance, Wel<come>1% string could be used as follows:

SET "userid=root"
SET "passwd=Wel<come>1%%"

for /f "delims=" %%i in ('type "ipaddress.txt" ') do (
  pushd "C:\Program Files (x86)\PuTTY"
  SETLOCAL EnableDelayedExpansion
    plink.exe -pw !passwd! %userid%@%%i hostname
  ENDLOCAL
  popd
)