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Hi, I just wondering how to Passing structures of array to functions

Here is my code

#include <stdio.h>

struct harbour 
{
    int harbourId;
    int maxCap;
    int timeUpload;
    double amount;
    
};

struct ship
{
    int number;
    int shipId;
    int sMaxCap;
    int sActCap;
    int aTime;
};
void readHarbour()
{
    int i=0, lineCount=0;
    struct harbour dock[100]; 
	FILE *harbourf;
	harbourf = fopen("data.txt","r");
    do 
    {
        fscanf(harbourf, "%d %d %d %lf", &dock[i].harbourId, &dock[i].maxCap, &dock[i].timeUpload, &dock[i].amount);
        
        lineCount++;
        i++;
    } while (feof(harbourf) == 0);
 
}
void readShip()
{
    int i=0, lineCount=0;
    struct ship ship[100]; 
	FILE *shipf;
	shipf = fopen("data2.txt","r");
    do 
    {
        fscanf(shipf, "%d %d %d %d", &ship[i].shipId, &ship[i].sMaxCap, &ship[i].sActCap, &ship[i].aTime);
        
        lineCount++;
        i++;
    } while (feof(shipf) == 0);

}
void processing(int lineCount)
{
    // pass to here 
}
    
}

int main() 
{
    struct harbour h[100];
    struct ship s[100];
    
    readShip(s);
	readHarbour(h);    
    return 0;
}
  • 2 Contributors
  • 1 Reply
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  • 16 Hours Discussion Span
  • Latest Post Latest Post by thines01

Dani AI

Generated

’s problem is that the arrays are created inside readHarbour() / readShip() and vanish when those functions return. As suggested, pass the destination from main — but also pass a capacity, return the number of items read, and check file/scan results. Avoid feof() as the loop condition; use the return value from fscanf() (or read lines with fgets() + sscanf()).

Example pattern (robust, minimal):

#include <stdio.h>
#include <stddef.h>

typedef struct { int id; int capacity; int upload_time; double amount; } Harbour;
typedef struct { int id; int max_cap; int act_cap; int arrival; } Ship;

/* returns number read, 0 on error or empty file */
size_t read_harbours(Harbour out[], size_t max, const char *path)
{
    FILE *f = fopen(path, "r");
    if (!f) return 0;
    size_t n = 0;
    while (n < max) {
        int got = fscanf(f, "%d %d %d %lf",
                         &out[n].id, &out[n].capacity,
                         &out[n].upload_time, &out[n].amount);
        if (got == EOF) break;
        if (got != 4) { /* handle or skip malformed line */ break; }
        n++;
    }
    fclose(f);
    return n;
}

/* processing should accept pointers + counts */
void processing(const Harbour docks[], size_t docks_n,
                const Ship ships[], size_t ships_n);

Key points and troubleshooting:

  • Declare arrays in main (or malloc and return a pointer) and pass them in. Local arrays in a function do not survive return.
  • Always check fopen() and the return value of fscanf(); a mismatched format string will break the loop.
  • Return the actual count read and use size_t for sizes.
  • Use const in processing() when inputs are not modified.
  • If parsing fails, print or log the offending line (use fgets() for that) to debug input-format problems.
  • Keep the format string and file data in sync; small typos in the format are the most common source of silent failures.
Member Avatar for thines01

Change your readShip and readHarbour function signatures to accept the pointers of your structures.
Example:

typedef struct HARBOUR 
{
    int harbourId;
    int maxCap;
    int timeUpload;
    double amount;
} harbour;

void readHarbour(harbour* docks)
{
	// code goes here
}

int main(void)
{
	harbour docks[100] = {0};
	readHarbour(docks);
	return 0;
}
Edited by thines01 because: clarity
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