Reads City - Temp pairs from file, sorts, and write out

homerseklet.c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#define MAX_TEMP 100
#define NAME_LEN 128
struct city_data{

    char name[128];
    int temp;
};
void xchg(struct city_data *left,struct city_data *right)
{
    char name[NAME_LEN];
    int temp;
    strcpy(name,left->name);
    temp=left->temp;
    strcpy(left->name,right->name);
    left->temp=right->temp;
    strcpy(right->name,name);
    right->temp=temp;
}
//left->temp == (*left).temp
int main(){
    FILE *fr;
    FILE *fw;
    char row[255];
    char *token;

    unsigned n=0,min_index=0;
    int i,changed=1;
    struct city_data cd[MAX_TEMP];
    fr = fopen("homerseklet.txt", "r");
    while (fgets(row, 255, fr) != NULL)  {
      if ((strlen(row)>0) && (row[strlen (row) - 1] == '\n'))
        row[strlen (row) - 1] = '\0';
      token = strtok(row," ");
      strcpy(cd[n].name, token);
      token = strtok(NULL, " ");
      cd[n].temp = atoi(token);
      n++;
    }

    for(i=1;i<n;i++){
        if(cd[i].temp<cd[min_index].temp){
            min_index=i;
        }
    }
    while(changed){
    changed=0;
    for(i=0;i<n-1;++i){
        if(cd[i].temp>cd[i+1].temp){
           changed=1;
            xchg(&cd[i],&cd[i+1]);
            }
        }
    }
    fw = fopen("homerseklet_rendezett.txt", "w+");
    for (i=0;i<n;++i){
      fprintf(fw, "%s %i\n", cd[i].name,cd[i].temp);
    }
    return 0;
}