c - detecting no argument with getopt_long -

how detect user passed no arguments program getopt_long? detect user calling program no arguments checking argc, user calling program dash?

$ my_prog - 

do need include option somehow in getopt statement?

while(ca = getopt_long(argc, argv, "abc:d:",...) 

what function return?

you can use optind variable determine such arguments:

the variable optind index of next element of argv[] vector processed. shall initialized 1 system, , getopt() shall update when finishes each element of argv[].

for example,

  for(int = optind; < argc; i++)     printf("unknown argument: %s\n", argv[i]); 

you can after argument processing find out if there such unexpected arguments.