Question

I’m trying to compare a string stored in a structure. I’m using scanf to input a string and I need to search for the string in the structure. Here is the code I have:

int printing_airports(int all_routes_size,int all_airports_size){

  int i,position;
  char airport;
  printf("Enter airport code:  ");
  scanf("%s", airport);

  for(i=0;i<all_airports_size;i++){
    if(strcmp(airport,all_airports_divid[i].code) == 0){
      position = i;
    }
  }
  printf("%s",all_airports_divid[position].code);
}

This is how I declared my structures

struct all_routes{
  int id;
  char departure_code[4];
  char arrival_code[4];
};
struct all_routes all_routes_divid[500];

This is the error I’m getting when I tried to compile

y:~/enee150/project2: compile
functions.c: In function 'printing_airports':
functions.c:370:15: error: invalid type argument of unary '*' (have 'int')
functions.c:373:5: warning: passing argument 1 of 'strcmp' makes pointer from integer without a cast [enabled by default]
/usr/include/iso/string_iso.h:64:12: note: expected 'const char *' but argument is of type 'char'

What am I doing wrong? Please help me.

Answer 1

You declare airport as a char

char airport;

but use it as a string. Declare it char airport[100]; or so.

printf("Enter airport code:  ");
scanf("%s", airport);

scanf requires a pointer to the variable the result shall be stored in as argument. When declared as char, airport is passed as an int to scanf, that is why the first message mentions int. The argument is dereferenced (unary *) to find the location where to store the scan result.

for(i=0;i<all_airports_size;i++){
  if(strcmp(airport,all_airports_divid[i].code) == 0){

strcmp requires a pointer (to a 0-terminated string) as argument. If passed an integral type like char, without explicit cast, the compiler warns about that (because 99.99+% of the time it’s wrong to do that).