Taking command line options in C -

i have hash table program , i'm trying implement command line option inputs. default action create hash table , read in text file, done after checking options. options alter properties of hash table before creation, e.g -f option specifies table size.

e.g ./program < words.txt -f 400

i'm handling them this:

int main(int argc, char*argv[]){      const char *optstring = "e:f:";     char option;     int tablesize = 100;     int unknown_words, i;     char word[256];     htable h;        default = 1;      while((option = getopt(argc, argv, optstring)) != eof){         switch (option){              case 'e':                 default = 0;                 h = htable_new(tablesize);                  copy_in(h);                  unknown_words = find_words(h, optarg);                 printf("%d", unknown_words);                 break;               case 'f':                  if(optarg && atoi(optarg)>0){                        tablesize = atoi(optarg);                            }                 break;         }      }       if(default==1){          h = htable_new(tablesize);          copy_in(h);          print_stats(h);      }   } 

my issue want enter these flags/options in order. have option -e takes argument (the name of second text file). creates hash table , reads in first text file (like default action) searches hash table words in second file , prints unknown number of words. have option -f specifies use different table size default. if run below command expected behaviour.

./program < words.txt -f 350 -e other_words.txt  

the -f option found first , tablesize variable changed default value given 350. -e option found , carried out using updated value.

however in different order same desired behaviour:

./program < words.txt -e other_words.txt -f 350 

the -e option carried out on default table size , afterwards -f option found , tablesize changed , not used.

i've done below works seems inefficient. if -e option found, loop through remaining options , them first. means duplicate code each relevant option though , i'm curious how else handle this.

 while((option = getopt(argc, argv, optstring)) != eof){         switch (option){              case 'e':                 default = 0;                 for(i=optind;i<argc;i++){                     if(strcmp(argv[i],"-t") == 0){                         if(argv[i+1] && atoi(argv[i+1])>0){                              tablesize =atoi(argv[i+1]);                         }                      }                  }                   h = htable_new(tablesize);                  copy_in(h);                  unknown_words = find_words(h, optarg);                 printf("%d", unknown_words);                 break;               case 'f':                  if(optarg && atoi(optarg)>0){                        tablesize = atoi(optarg);                            }                 break;         }      } 

the typical approach not actual work in option handlers; instead let each handler set variable keep track option specified (and argument was). after parse command line options, can process them in whatever order want. example, like:

const char* filename = null; int tablesize = 0;  while ((option = getopt(argc, argv, optstring)) != eof) {     switch (option) {         case 'e':             filename = optarg;             break;           case 'f':             if (optarg && atoi(optarg) > 0) {                 tablesize = atoi(optarg);                        }             break;     } }  if (filename != null) {     default = 0;     h = htable_new(tablesize);      copy_in(h);     unknown_words = find_words(h, filename);     printf("%d", unknown_words); }