Using PowerShell variable for example in FTP.exe - variables

Question

How do you use powershell variables when you run program in it? Is it simply not possible?
Example:
$url = "test.com"
ftp
ftp> open $url
Unknown host $url.

Answer 1

The FTP command will read commands from a file, so you can use Powershell to create a file containing the required commands and then tell the command to read from the file. It is best to create a unique name for the temporary file and remember to delete it when you are finished:
PS C:\> $url = "test.com"
PS C:\> $filename = "foo.bar"
PS C:\> $tempFile = [io.path]::GetTempFileName()
PS C:\> #"
>> open $url
>> get $filename
>> quit
>> "# >>$tempFile
>>
PS C:\> cat $tempFile
open test.com
get foo.bar
quit
PS C:\> ftp -s:$tempFile
PS C:\> remove-item $tempFile
A multi-line string #"..."# is a good way to create a temporary file for external commands because it lets you write the commands in a natural way.
Other commands may not accept input from a file. In that case it is worth checking whether you can specify all of the needed commands on the command line. Many non-Powershell commands will actually accept multi-line arguments even though when run from cmd.exe there would be no way to pass such arguments. For example:
PS C:\python34> python -c #"
>> for i in range(10):
>> print(i)
>> "#
>>
0
1
2
3
4
5
6
7
8
9
PS C:\python34>