FILE *__pmOpenLog(const char * progname , const char * logname , FILE * oldstream , int * status );
On return, the function value is the new standard I/O stream. In the event of an error, this will be oldstream unchanged and status will be 0.
is 1, a standard preamble is written to
Log for progname on hostname started date and time
and an atexit (3) handler is installed to write the postscript message to logname
Log finished date and time
when the processes exits.