strcmp-Multiple Strings

Goal: Send error sms if unknown command is received

My device can accept 4 commands via SMS. The sms body is stored in _4G._buffer.
- Relay1 On
- Relay1 Off
- Relay2 On
- Relay2 Off
Using strcmp, if the text message contains any of those, I activate a digital input.
.
** ** if (strcmp(_4G._buffer, "Relay2 on") == 0 ) {       digitalWrite(relay2, LOW);     }     else {}** **
I am now looking to implement a feature that will send a text message saying command not recognized if anything besides the commands above are received.
I try:
** **if (strcmp(_4G._buffer, "Relay1 on" | "Relay1 off" | "Relay2 on" | "Relay2 off") == 0) //if sms says any of these proper commands {   //do nothing, as other lines of code will open/close the valve }   else {     smsSend("Command not reconized"); // send error SMS     }** **
And get this compile error:
exit status 1
invalid operands of types ‘const char [10]’ and ‘const char [11]’ to binary 'operator|'
I am unsure where I am making the mistake. Any help would be greatly appreciated.
Thanks

You have to have a strcmp per string.

Bitwise ORing a string makes no sense whatsoever.

AWOL:
You have to have a strcmp per string.

Bitwise ORing a string makes no sense whatsoever.

Are you suggesting

 if (strcmp(_4G._buffer, "Relay1 off") == 0 ) {
     
    }
    else {
SendError;
}

Wont that affect other lines that I have that say

    if (strcmp(_4G._buffer, "Relay2 off") == 0 ) {
    
    }
    else {
SendError;
}

You only send error once and that is if the previous four conditions fail, note “else if”

if(strcmp(_4G._buffer,"Relay1 on")==0)
{
 digitalWrite(Relay1,LOW);  
}
else if(strcmp(_4G._buffer,"Relay1 off")==0)
{
 digitalWrite(Relay1,HIGH); 
}
else if(strcmp(_4G._buffer, "Relay2 on")==0)
{
 digitalWrite(Relay2,LOW);    
}
else if(strcmp(_4G._buffer,"Relay2 off")==0)
{
 digitalWrite(Relay2,HIGH);  
}
else 
{
SendError;   
}