• char*
  string to be sent to caller output
• int
  identification number of calling ngspice shared lib (default is 0, see Chapt. 19.6)
• void*
  return pointer received from caller during initialization, e.g. pointer to object having sent the request

Sending output from stdout, stderr to caller. ngspice printf, fprintf, fputs, fputc functions are redirected to this function. The char* string is generated by assembling the print outputs of the above mentioned functions according to the following rules: The string commences with `stdout ', if directed to stdout by ngspice (with `stderr ' respectively); all tokens are assembled in sequence, taking the printf format specifiers into account, until `\n' is hit. If set addescape is given in .spiceinit, the escape character \ is added to any character from $[]\" found in the string.

Each callback function has a void pointer as the last parameter. This is useful in object oriented programming. You may have sent the this (or self) pointer of the caller's class object to ngspice.dll during calling ngSpice_Init (19.3.2.1). The pointer is returned unmodified by each callback, so the callback function may identify the class object that has initialized ngspice.dll.