The /P switch allows you to set the value of a variable to a line of input entered by the user. Displays the specified promptString before reading the line of input. The promptString can be empty.
Two ways I’ve used it… first:
SET /P variable=
When batch file reaches this point (when left blank) it will halt and wait for user input. Input then becomes variable.
And second:
SET /P variable=<%temp%\filename.txt
Will set variable to contents (the first line) of the txt file. This method won’t work unless the /P is included. Both tested on Windows 8.1 Pro, but it’s the same on 7 and 10.