PowerShell: **reading** input from the keyboard AND **redirecting output** to a variable/file

Question

Sorry if my question is trivial; I'm a beginner with PowerShell.

My program (plink) is expecting for an answer from the keyboard and will return some output. Is it possible to redirect the output to a variable/file?

Details:

_{(I am assigning the command, itself, to a variable, for convenience.)}

Without output redirection — Console output is OK:

PS C:\Users\user> $mycmd="plink -v -ssh -l $user $myserver vncserver -list"
PS C:\Users\user> invoke-expression $mycmd
user@server's password:
TigerVNC server sessions:
X DISPLAY #     PROCESS ID
:1              26788
PS C:\Users\user>

However with output redirection in to a variable:

PS C:\Users\user> $myoutput=invoke-expression "$mycmd"

...still waiting in this state ==> I type my passwd blindly (passwd prompt is captured in $myoutput)

PS C:\Users\user> $myoutput

user@server's password:

TigerVNC server sessions:

X DISPLAY # PROCESS ID

PS C:\Users\server>

$myoutput variable contents is OK But the password prompt is redirected in to the variable too !

My pbm now is how to make usage comprehensive :user can't guess when typing his passwd :( (i.e. how to handle the password prompt?)

Remarqs: verbose mode of plink (plink -v ...) still outputting to the console when redirecting to $myoutput

$myoutput=invoke-expression "$mycmd"

Looking up host "server"
Connecting to xxx.XXX.XXX.XXX port 22
We claim version: SSH-2.0-PuTTY_Release_0.66
Server version: SSH-2.0-OpenSSH_7.4
Using SSH protocol version 2
Doing Diffie-Hellman group exchange
Doing Diffie-Hellman key exchange with hash SHA-256
Host key fingerprint is:
ssh-rsa 2048 blabklablablablabla
Initialised AES-256 SDCTR client->server encryption
Initialised HMAC-SHA-256 client->server MAC algorithm
Initialised AES-256 SDCTR server->client encryption
Initialised HMAC-SHA-256 server->client MAC algorithm
Using username "user".
Using SSPI from SECUR32.DLL
Attempting GSSAPI authentication
GSSAPI authentication initialisation failed
The target was not recognized.

I enter my passwd here (in the dark)

Sent password
Access granted
Opening session as main channel
Opened main channel
Started a shell/command
Server sent command exit status 1
Disconnected: All channels closed

Answer 1

The password prompt is part of the output from plink, so you should expect it to go into $myoutput and not to the console.  I expect that, when you type $myoutput=invoke-expression "$mycmd", it just seems to hang, and doesn’t give you another PS prompt.  It is probably silently reading the password from the keyboard!  If you just go ahead and type the password, it will work.  (Warning: the password may display on the console screen.)

As mentioned above, since the password prompt is part of the output from plink, it goes into $myoutput.  So, you need to be prepared to handle the first line of $myoutput being the password prompt.