The Execute Command routine stops program execution and directs
    the command language interpreter (CLI) to execute a command
    that you supply as the argument. If successful, LIB$DO_COMMAND
    does not return control to the calling program. Instead, LIB$DO_
    COMMAND begins execution of the specified command.

    If you want control to return to the caller, use LIB$SPAWN
    instead.

    Format

      LIB$DO_COMMAND  command-string

1 - Returns

    OpenVMS usage:cond_value
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value

2 - Argument

 command-string

    OpenVMS usage:char_string
    type:         character string
    access:       read only
    mechanism:    by descriptor

    Text of the command that LIB$DO_COMMAND executes. The command-
    string argument is the address of a descriptor pointing to
    the command text. The maximum length of the command is 255
    characters.