• Christian Hesse's avatar
    global: variable names are CamelCase · 870f00bb
    Christian Hesse authored
                ___  _         ___     __
               / _ )(_)__ _   / _/__ _/ /_
              / _  / / _ `/  / _/ _ `/ __/
             /____/_/\_, /  /_/ \_,_/\__/
     _       __     /___/       _             __
    | |     / /___ __________  (_)___  ____ _/ /
    | | /| / / __ `/ ___/ __ \/ / __ \/ __ `/ /
    | |/ |/ / /_/ / /  / / / / / / / / /_/ /_/
    |__/|__/\__,_/_/  /_/ /_/_/_/ /_/\__, (_)
                                    /____/
    
    RouterOS has some odd behavior when it comes to variable names. Let's
    have a look at the interfaces:
    
    [admin@MikroTik] > / interface print where name=en1
    Flags: D - dynamic, X - disabled, R - running, S - slave
     #     NAME                                TYPE       ACTUAL-MTU L2MTU
     0  RS en1                                 ether            1500  1598
    
    That looks ok. Now we use a script:
    
    { :local interface "en1";
      / interface print where name=$interface; }
    
    And the result...
    
    [admin@MikroTik] > { :local interface "en1";
    {...   / interface print where name=$interface; }
    Flags: D - dynamic, X - disabled, R - running, S - slave
     #     NAME                                TYPE       ACTUAL-MTU L2MTU
     0  RS en1                                 ether            1500  1598
    
    ... still looks ok.
    We make a little modification to the script:
    
    { :local name "en1";
      / interface print where name=$name; }
    
    And the result:
    
    [admin@MikroTik] > { :local name "en1";
    {...   / interface print where name=$name; }
    Flags: D - dynamic, X - disabled, R - running, S - slave
     #     NAME                                TYPE       ACTUAL-MTU L2MTU
     0  RS en1                                 ether            1500  1598
     1   S en2                                 ether            1500  1598
     2   S en3                                 ether            1500  1598
     3   S en4                                 ether            1500  1598
     4   S en5                                 ether            1500  1598
     5  R  br-local                            bridge           1500  1598
    
    Ups! The filter has no effect!
    That happens whenever the variable name ($name) matches the property
    name (name=).
    
    And another modification:
    
    { :local type "en1";
      / interface print where name=$type; }
    
    And the result:
    
    [admin@MikroTik] > { :local type "en1";
    {...   / interface print where name=$type; }
    Flags: D - dynamic, X - disabled, R - running, S - slave
     #     NAME                                TYPE       ACTUAL-MTU L2MTU
    
    Ups! Nothing?
    Even if the variable name ($type) matches whatever property name (type=)
    things go wrong.
    
    The answer from MikroTik support (in Ticket#2019010222000454):
    
    > This is how scripting works in RouterOS and we will not fix it.
    
    To get around this we use variable names in CamelCase. Let's hope
    Mikrotik never ever introduces property names in CamelCase...
    
    *fingers crossed*
    870f00bb
ip-addr-bridge 618 Bytes