Description of problem:

These lines in src/spicelib/analysis/dctran.c broke ngspice in server mode since they write on stdout at the same time than the function src/frontend/outitf.c:OUTpData that write the output in binary mode:

#ifdef NDEV
                /* show a time process indicator, by Gong Ding, gdiso */
                if(ckt->CKTtime/ckt->CKTfinalTime*100<10.0)
                    printf("%%%3.2lf\b\b\b\b\b",ckt->CKTtime/ckt->CKTfinalTime*100);
                else  if(ckt->CKTtime/ckt->CKTfinalTime*100<100.0)
                    printf("%%%4.2lf\b\b\b\b\b\b",ckt->CKTtime/ckt->CKTfinalTime*100);
                else
                    printf("%%%5.2lf\b\b\b\b\b\b\b",ckt->CKTtime/ckt->CKTfinalTime*100);
                fflush(stdout);
#endif

The serialised double array is thus spoiled by many "%xx.xx\b\b\b\n". 

They are only included if we enable ndev.

I suggest to remove these lines by applying a patch.