String / segmentation fault

/*                                                                           
  Program to calculate trip and plan flights                                 
*/
#define TRIP 6
#define NAMEMAX 40
#define DEST 1

#include <stdio.h>
#include <string.h>


int main(void)
{
  int i, trip_num, row, col;
  char travel_name[TRIP][DEST],
    dest_in[1];


  printf("Please enter the number of trips:");
  scanf("%d", &trip_num);

  while (trip_num > TRIP)
    {
      printf("Invalid number of trip. (Min of 3 trips and Max 6 tri开发者_运维百科ps).\n");\
  /*input number of trips*/
      printf("Please enter the number of trips:");
      scanf("%d", &trip_num);
      if (trip_num < TRIP)
        printf("Valid trip number. Please proceed to enter destination code.\
\n");
    }

  for (i=0; i < trip_num ; i++)

    {
      printf("Please enter name of destination(Note: use _ to for spaces in \
name):\n");
      scanf("%s", &dest_in);
      if (strlen(dest_in) < NAMEMAX)
        strcpy(travel_name[i],dest_in);
   /*   else (strlen(dest_in) > NAMEMAX) */



  for (row = 0; row < trip_num; row++)
    {
      for (col=0; col < DEST; col++)
        printf("Trip#:%d travel_name:%s \n", row+1, travel_name[row][col]);
    }

  return 0;
}

I'm trying to get the user to put in a name as string and store it if the name is 40 character or less but its giving me a segmentation fault

trip_num is not initialized. It is unknown how many times the for loop executes so:

travel_name[i][0]=dest_in[100];

could be writing past the end of the array. Also, what is the purpose of that statement? I don't really follow what it is trying to do so I would start by figuring that out.

There are lots of problems with your code.

1. scanf("%s", &dest_in) will read a string into dest_in which could potentially overflow your buffer because there is no size specifier. Consider changing it to scanf("%99s", dest_in) so you read 99 characters maximum, + 1 for the null terminator which is 100 (your array size). Also, there is no need to use to & operator here.

2. travel_name[i][0]=dest_in[100]; You are accessing a character that is outside the bounds of dest_in. The only index you should access is 0.

3. printf("Trip#:%d travel_name:%s \n", row+1, travel_name[row][col]); Your code says that you want to print a string. printf goes looking for a pointer to a character array but travel_name[row][col] is a single character.

4. while (trip_num > TRIP). You tell the user to enter a number between 3 and 6 but you don't check if the input is less than 3.

I think it's because --> What is trip_num ?

These types of problems can be easily solved through the use of a debugger. May I suggest learning gdb (or cgdb) or perhaps an outright IDE with built-in debugging capabilities like Eclipse CDT.