c - getopt switch statement never hitting default case -

c - getopt switch statement never hitting default case -

i've tried searching , haven't found duplicate/similar question.

how come "default" never triggering in case? working on previous homework assignments course of study prepare fall, , i'm having issue getopt() in c.

here particular lines in question:

while ((c = getopt(argc, argv, "i:o:")) != -1) { switch (c) { case 'i': infile = strdup(optarg); break; case 'o': outfile = strdup(optarg); break; default: usage(); //this prints "usage" statement , exits cleanly. } }

my issue is, how come calling

./fastsort b c d

doesn't print usage , exit?

the below code search options -i hello or/and -o world

while((c = getopt(argc, argv, "i:o:") != -1)

however executing is:

./fastsort b c d

where getopt(argc, argv, "i:o:") != -1 not satisfied since none of passed argument a b c dis option

c command-line-arguments getopt